Dissertations / Theses on the topic 'Modulation de position d’impulsion'
To see the other types of publications on this topic, follow the link: Modulation de position d’impulsion.
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Modulation de position d’impulsion.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Boussebt, Amina. "Etude et mise en oeuvre de la technologie Li-Fi pour un lit de bébé connecté sans fil et sans radio." Electronic Thesis or Diss., Limoges, 2023. http://www.theses.fr/2023LIMO0091.
Full textAbstract:
Le domaine de la télésurveillance a connu un grand essor ces dernières décennies et concerne divers contextes par exemple en milieu hospitalier, en maison de retraite, chez les particuliers. La majorité des systèmes de télésurveillance existants aujourd’hui reposent sur la technologie des radiofréquences (RF). Nous proposons dans cette thèse, des travaux portant sur la télésurveillance dans un contexte nouveau qui concerne une crèche. Les RF présentant certains inconvénients, comme l’impact des interférences électromagnétiques, mais aussi des failles de sécurité, une solution alternative est la technologie de communication par optique sans fil. Ainsi, nous avons étudié l'utilisation de la technologie infrarouge pour la transmission simultanée de données issues de capteurs placés sur les pieds des lits de bébé mais aussi sur les bébés couchés dans leur lit au sein de la crèche. Le système de réception est constitué de photodiodes situées aux coins d'un panneau d'éclairage central au plafond de l'environnement. La simulation du canal réalisée grâce à la technique de lancer de rayons associés à la méthode de Monte-Carlo a permis de déterminer le gain du canal pour chaque dispositif. Plusieurs scénarios de déploiement ont été définis en considérant le caractère amovible ou fixe des dispositifs et l’interchangeabilité des lits dans la pièce. Le partage du canal utilise la technique d’accès multiple par répartition de codes (OCDMA) associée aux codes optiques orthogonaux (OOC) dont la principale limitation est l’interférence d’accès multiple (IAM). Les performances de la modulation binaire par position d’impulsion (2-PPM) avec OCDMA et un décodage souple en réception ont été établies théoriquement et par simulation pour les différents scénarios définis considérant un réseau de 11 utilisateurs constitué de 8 lits et 3 dispositifs portés par des bébés. Les résultats ont été obtenus avec des récepteurs conventionnels par corrélation sans et avec limiteur puis un récepteur à annulation parallèle d’interférence plus efficace pour réduire l’impact de l’IAM. De plus, la faisabilité de l’utilisation de la technique OCDMA pour la transmission simultanée en optique sans fil a été mise en évidence par des expérimentations menées grâce à un banc de test développé en radio logicielle. Le banc a été mis en place, en utilisant des USRP (Universal Software Radio Peripheral) et des front-ends optique sans fil développés spécifiquementThe field of the remote monitoring has experienced significant advancements in recent decades, and now covers different contexts, such as hospitals, retirement homes, and private homes also. The majority of existing systems are based on radio frequency technology (RF).We propose in this thesis, research focused on remote monitoring in a new context involving a nursery. Given the limitations of RF technology, including the impact of electromagnetic interference, and security vulnerabilities, an alternative solution is optical wireless communication technology. Therefore, we investigated the use of infrared technology for simultaneous transmission of data collected from sensors placed on the foot of baby beds, and also on the babies themselves lying in their beds within the nursery. The reception system consists of photodiodes positioned at the corners of a central lighting panel on the celling. The channel simulation carried out using ray-tracing and Monte-Carlo methods was used to determine the channel gain for each device. Several deployment scenarios were defined, considering the nature of the devices (removable or fixed) and the interchangeability of beds in the room. The channel sharing employs the code division multiple access (OCDMA) associated with the optical orthogonal codes (OOC) with the primary constraint being the137 multiple access interference (MAI). The performance of binary pulse position modulation (2- PPM) with OCDMA and soft decoding in reception was studied theoretically and by simulation involving the different scenarios. These scenarios consider a network of 11 users, consisting of 8 beds and 3 devices carried by babies. Results were obtained using the conventional correlation receiver without and with hard limiters, as well as a parallel interference cancellation receiver to reduce the impact of MAI. Additionally, the feasibility of implementing OCDMA technology for simultaneous optical wireless communication transmission was demonstrated through experimental work using a test bench developed in software-defined radio. The test bench was established using universal software radio peripheral (USRP), and specially designed wireless optical front-ends
2
Ray, Indrani. "Analysis of offset pulse position modulation." Thesis, University of Huddersfield, 2015. http://eprints.hud.ac.uk/id/eprint/24847/.
Full textAbstract:
This work presents the performance analysis of the offset pulse position modulation (PPM) scheme using graded-index plastic optical fibre with a Gaussian impulse response. The aim of this analysis is to predict how sensitivity, error, number of required photons, threshold voltage, and the effect of inter-symbol interference will change with the change in the number of data bits encoded at a rate of 1 Gbit/s. An information theory analysis is presented in detail and also the band-utilization efficiency is determined. Results are compared to equivalent digital PPM and multiple PPM schemes and it is also shown that offset PPM gives an advantage over on-off keying (OOK). Bit error rate (BER) analysis has been presented numerically. The errors due to different coding techniques are compared. It has also been shown that offset pulse position modulation is more power efficient than multiple pulse position modulation. The spectral analysis of offset pulse position modulation coding scheme has been carried out. For an offset PPM sequence the spectral characteristics is presented both theoretically and numerically. The results show strong frequency components at the frame rate and, if return-to-zero pulses are used, the slot rate. Slot synchronisation has been taken into consideration for the first time as offset PPM spectrum exhibits discrete slot rate component. The effect of pulse shaping and modulating index on the spectrum has been shown. The dependency of slot component on the pulse shape is examined. The results show that the frame synchronisation is possible for offset PPM as this coding exhibits a strong frame rate component. A comparison of spectral characteristics has been presented considering digital, multiple and shortened PPM. For ease of implementation an offset PPM coder has been designed. In this work an efficient clock recovery topology is presented for offset PPM data sequence at the receiver end. For clock recovery, a phase locked loop is designed. Data recovery has also been presented. It is shown that a frame clock can be extracted from the data sequence that yields the possibility of frame synchronization. A detailed noise analysis has been performed for random offset PPM input. It has been shown that the proposed clock recovery system is also effective for extracting other data sequence. To elucidate, a multiple Pulse Position Modulation (MPPM) data sequence is considered. The MPPM data sequence has also been synchronised with the recovered clock. A noise analysis is carried out for multiple PPM.
3
Mahmood, Faaiz Hadi. "Implementation of Offset Pulse Position Modulation." Thesis, University of Huddersfield, 2017. http://eprints.hud.ac.uk/id/eprint/34409/.
Full textAbstract:
Optical fibre systems have played a key role in making possible the extraordinary growth in world-wide communications that has occurred in the last 25 years, and are vital in enabling the proliferating use of the Internet. Its high bandwidth capabilities, low attenuation characteristics, low cost, and immunity from the many disturbances that can afflict electrical wires and wireless communication links make it ideal for gigabit transmission and a major building block in the telecommunication infrastructure. The main concern of this thesis is a full and detailed investigation and implementation of the Offset Pulse Position Modulation (Offset PPM) communication system. Novel work is carried out for applying Offset PPM over an optical communication channel theoretically and experimentally to examine the system performance. An Offset PPM encoder and decoder were implemented to code Pulse Code Modulation (PCM) format into Offset PPM format and to decode back the Offset PPM to PCM. The first paradigm of implementation was implemented using electronic components. A further investigation took place on the Offset PPM associated output. Computer programming and simulation using the VHSIC Hardware Description Language (VHDL) of this PPM code was considered and comparison with previous theoretical results presented. The received Offset PPM signal returned back to its original input PCM form without errors. Successful VHDL and Field Programmable Gate Array (FPGA) implementation using Altera Quartus II of Offset PPM encoder and decoder as a single system has been presented in the study. An FPGA embedded Bit Error Rate (BER) test device has also been implemented for sensitivity measurements purposes and all the designs have been tested successfully with back-to-back testing. Results show that Offset PPM is an advantageous PPM code for optic communication. Furthermore, the system has achieved a very high data rate of 50 Mb/s without an optical communication set. An optical communication system (transmitter/receiver) over POF was developed and the Offset PPM scheme was investigated through this optical channel. Results show that the Offset PPM sequence transferred through the optic system without being altered. In addition, this implementation is optimised PPM coding; the system is working perfectly with up to 10 Mb/s with 10-12 BER based on the limitations of the optical communication set. All the results and analyses indicate that Offset PPM is an ideal alternative to be considered for highly dispersive optical channels, and performance evaluation for higher bandwidths also favourably compares to existing coding schemes.
4
Phillips, Andrew Julian. "Optically amplified digital pulse position modulation systems." Thesis, Manchester Metropolitan University, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.260069.
Full text
5
Alahmari, Abdallah Said. "Turbo coded pulse position modulation for optical communications." Diss., Georgia Institute of Technology, 2003. http://hdl.handle.net/1853/15388.
Full text
6
Cryan, Robert Anthony. "High sensitivity optical digital pulse position modulation systems." Thesis, University of Huddersfield, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.306086.
Full textAbstract:
Digital pulse position modulation (PPM) is a transmission format that can be used to exchange excess channel bandwidth for improved receiver sensitivity. This thesis is concerned with the performance of digital PPM for use in optical fibre systems such that increased single-span transmission distances can be achieved. It includes a literature survey and a thorough theoretical investigation into uncoded directly detected and coherently detected digital PPM, along with an evaluation of forward error correction coded PPM. Original contributions are described for digital PPM systems employing PIN-BJT transimpedance and PIN -FET high impedance pre-amplifiers. In the PIN -BJT case, a new analysis is presented that accounts for the band-limiting effect of the preamplifier and the non-white noise power spectral density, resulting from equalisation. For the PIN-FET, a causal noise-whitening filter is considered and the factors that limit the maximum bit-rate determined. By using an upper Chernoff Bound to the average binary error probability, results are calculated for APD-BJT and APD-FET PPM systems. The practical implementation of the optimal PPM filter is considered and two novel techniques are described for automating the realisation process. Coherent PPM is investigated and new work is presented for Reed-Solomon coded homodyne PPM. The influence of the Reed-Solomon code rate on receiver sensitivity is studied and it is shown that a 3/4 code rate leads to optimum sensitivity. Digital PPM employing soliton pulses is examined and it is shown that, under ideal conditions, a higher bit-rate than PCM can be achieved. The influence of timing jitter, associated with soliton pulse energy fluctuations and the Gordon-Haus effect, on the performance of digital PPM is investigated. The simplification of the PPM pre-detection filter is studied and a range of suboptimum filters investigated. The calculations demonstrate that the optimal predetection filter can be replaced by a simple 3rd order filter without incurring a severe sensitivity penalty. The sensitivity results of the various digital PPM systems investigated in this thesis are compared to those of equivalent PCM systems. It is illustrated that digital PPM offers an improvement of between 5-10 dB depending upon which coding format/ detection technique is employed. This represents an increase in transmission distance of 25-50 km and demonstrates that digital PPM is a promising modulation format and has potential for future high performance telecommunication routes.
7
Calvert, N. "An optical fibre digital pulse position modulation system." Thesis, University of Huddersfield, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.382254.
Full text
8
Bryant, Jack Alfred. "Position-dependent modulation of promoter activity in Escherichia coli." Thesis, University of Birmingham, 2013. http://etheses.bham.ac.uk//id/eprint/4197/.
Full textAbstract:
Bacterial gene expression is primarily regulated at the initial step of transcription initiation. This regulation has traditionally been viewed as due to the DNA sequence of promoters and factors that bind to them. However, the bacterial chromosome is a highly compacted and ordered structure. To date, the effects of position within the chromosome on promoter activity have barely been investigated. Here, I report that activity of a single promoter, inserted at different loci in the Escherichia coli chromosome, is dependent upon position within the chromosome. Quantification of genomic DNA at a number of loci showed this was unrelated to gene dosage. Drastic changes in position-dependent hierarchies of promoter activity were observed on entry into stationary phase. However, no correlation between the orientation of a promoter, with respect to replication, and its activity was found. Several factors are involved in this variation, including local sequence context. Increased promoter activity at origin-proximal loci was shown to be due to DNA supercoiling, maintained by the action of DNA gyrase. Transcription was shown to have a negative influence on the activity of downstream promoters. Further to this, the position of a promoter, with respect to a repressor-encoding gene, had an effect on its repression, further suggesting a role for genome organisation in the regulation of transcription. Finally, extended protein occupancy domains were shown to repress activity of inserted promoters, indicating that these domains act to silence the genes they encode. The combined data show that the position of a promoter within the E. coli chromosome plays a significant part in transcriptional regulation, and that structure of the chromosome is also likely to play a role.
9
Kumar, Kuldeep. "Pulse Position Modulation using BICM-ID for FSO Channels." International Foundation for Telemetering, 2013. http://hdl.handle.net/10150/579510.
Full textAbstract:
ITC/USA 2013 Conference Proceedings / The Forty-Ninth Annual International Telemetering Conference and Technical Exhibition / October 21-24, 2013 / Bally's Hotel & Convention Center, Las Vegas, NVWe investigate pulse position modulation (PPM) and multipulse PPM (MPPM) for free space op- tical channels using bit interleaved coded modulation with iterative decoding. Data bits are first encoded by using a non recursive convolutional code and the coded bits after an interleaver are modulated before transmission. Iterative decoding is performed at the receiver. Optimized mapping is designed for MPPM. A genetic algorithm is used to find the optimized mapping for MPPM. Our simulation results show that a significant improvement in the error performance can be achieved by using optimized mapping and iterative decoding at the receiver.
10
Hausien, H. H. "Pulse position modulation for optical fiber local area networks." Thesis, University of Bath, 1991. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.292804.
Full text
11
Wang, Y. "Linecoded digital pulse position modulation for repeatered optical fibre telecommunications." Thesis, University of Essex, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.376832.
Full text
12
Elmirghani, Jaafar Mohamed Hashim Mohamed Osman. "Frame and slot synchronisation for optical fibre digital pulse position modulation." Thesis, University of Huddersfield, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.359740.
Full text
13
Ashmore, Amy Frances. "Manual force modulation and position control in persons with Parkinson's disease /." Digital version accessible at:, 1998. http://wwwlib.umi.com/cr/utexas/main.
Full text
14
Massarella, A. J. "An experimental investigation into the detection of optical digital pulse-position modulation." Thesis, University of Huddersfield, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.314441.
Full text
15
Baker, Kenneth R. "Importance sampling simulation of free-space optical APD pulse position modulation receivers." Diss., This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-06062008-172207/.
Full text
16
Ghosna, Fadi Jawdat. "Pulse position modulation coding schemes for optical inter-satellite links in free space." Thesis, University of Huddersfield, 2010. http://eprints.hud.ac.uk/id/eprint/8766/.
Full textAbstract:
The rapid and significant development of communications links between satellites has made it possible to use various applications such as relay voice, video, multimedia, etc. As a result, a great deal of research has been done in this field during the last few years to reduce power consumption and increase transmission reliability. This thesis is concerned with an analysis of intersatellite links in free space, with optical links using laser sources being considered in particular. It includes a literature survey and a thorough theoretical investigation into designing the model of the link in free space. This thesis describes the novel technique of designing the optical receiver that consists of PIN photodiode as a photodetector, Semiconductor optical amplifier (SOA) and a 3rd order Butterworth filter with central decision detection. In addition, it discusses the use of several different coding schemes for use in such links: multiple pulse position modulation (MPPM); digital pulse position modulation (DPPM); Dicode pulse position modulation (Dicode PPM). This novel technique of an optical receiver is investigated and new work is presented in order to examine the noise performance of this optical receiver and hence determine its sensitivity and the number of photons received for a specified error rate. Further new work is carried out to compare these coding schemes in terms of error weightings and coding efficiency through showing how the PCM error rate is affected by false alarm and erasure errors for MPPM, DPPM and Dicode PPM coding 3, 4, 5 and 6 bits of PCM. An original maximum likelihood sequence detector (MLSD) is presented in this thesis in order to perform these comparisons. In addition, computer simulations models (using MCAD) are performed to compare these three coding schemes operating with 3, 4, 5 and 6 bits of PCM in terms of sensitivity and bandwidth efficiency. These comparisons show that MPPM coding 3, 4, 5 and 6 bits of PCM is the appropriate coding scheme to be used in optical inter-satellite links in free space and PCM data rates of 1 Gbit/s.
17
Buhafa, Adel Mohamed. "Investigation and implementation of dicode pulse position modulation over indoor visible light communication system." Thesis, University of Huddersfield, 2015. http://eprints.hud.ac.uk/id/eprint/26166/.
Full textAbstract:
A visible light communication (VLC) system with green technology is available and enables users to use white LEDs for illumination as well as for high data rate transmission over wireless optical links. In addition, LEDs have advantages of low power consumption, high speed with power efficiency and low cost. Therefore, a great deal of research is considered for indoor VLC, as it offers huge bandwidth whilst using a significant modulation technique. This thesis is concerned with the investigation and implementation of the dicode pulse position modulation (DiPPM) scheme over a VLC link using white LED sources. Novel work is carried out for applying DiPPM over a VLC channel theoretically and experimentally including a comparison with digital PPM (DPPM) in order to examine the system performance. Moreover, a proposal of variable DiPPM (VDiPPM) is presented in this thesis for dimming control. The indoor VLC channel characteristics have been investigated for two propagation prototypes. Two models have been proposed and developed with DiPPM and DPPM being applied over the VLC channel. A computer simulation for the proposed models for both DiPPM and DPPM systems is performed in order to analyse the receiver sensitivity with the effect of intersymbol interference (ISI). Both systems are operating at 100 Mbps and 1 Gbps for a BER of 10-9. An improvement in sensitivity being achieved by the DiPPM compared to the DPPM VLC system. The system performance has been carried out by Mathcad software. The predicted DiPPM receiver sensitivity outperforms DPPM receiver at by -5.55 dBm and -8.24 dBm, at 1 Gbps data rate, and by -5.53 dBm and -8.22 dBm, at 100 Mbps, without and with guard intervals, respectively. In both cases the optical receiver sensitivity is increased when the ISI is ignored. These results based on the received optical power required by each modulation scheme. Further work has been done in mathematical evaluation carried out to calculate the optical receiver sensitivity to verify the comparison between the two systems. The original numerical results show that DiPPM VLC system provides a better sensitivity than a DPPM VLC system at a selected BER of 10-9 when referred to the same preamplifier at wavelength of 650 nm and based on the equivalent input noise current generated by the optical front end receiver. The results show that the predicted sensitivity for DPPM is greater than that of DPPM by about 1 dBm when both systems operating at 100 Mbps and 1 Gbps. Also, it is show that the receiver sensitivity is increased when the ISI is limited. Experimentally, a complete indoor VLC system has been designed and implemented using Quartus II 11.1 software for generating VHDL codes and using FPGA development board (Cyclone IV GX) as main interface real-time transmission unit in this system. The white LEDs chip based transmitter and optical receiver have been constructed and tested. The measurements are performed by using LED white light as an optical transmitter faced to photodiode optical receiver on desk. Due to the LED bandwidth limitation the achieved operating data rate, using high speed LED driver, is 5.5 Mbps at BER of 10-7. The original results for the measurements determined that the average photodiode current produced by using DiPPM and DPPM optical receivers are 8.50 μA and 10.22 μA, respectively. And this in turn indicates that the DiPPM receiver can give a better sensitivity of -17.24 dBm while compared to the DPPM receiver which gives is -16.44 dBm. The original practical results proved the simulation and theoretical results where higher performance is achieved when a DiPPM scheme is used compared to DPPM scheme over an indoor VLC system.
18
Nikolaidis, Konstantinos. "An investigation of an optical multiple pulse position modulation link over a dispersive optical channel." Thesis, University of Huddersfield, 2008. http://eprints.hud.ac.uk/id/eprint/6980/.
Full textAbstract:
Digital Pulse Position Modulation (digital PPM) is a modulation format that codes n bits of PCM into a single pulse that occupies one of 2n time slots. Various studies over the last three decades have shown that such a scheme can offer an improvement in receiver sensitivity of 5-11 dB when compared to Pulse Code Modulation (PCM). Such an increase in sensitivity can be exploited beneficially in both long haul applications and the multi-user environment. However, this improvement results in a considerable increase in the final data rate of the original PCM, and this makes implementation difficult. Alternative methods have been proposed, such as multiple PPM, dicode PPM, differential PPM and overlapping PPM, that reduce transmission bandwidth while maintaining an increased sensitivity. Dicode and multiple PPM (MPPM) are the most bandwidth efficient of these formats and MPPM, the subject of this thesis, offers the best sensitivity without the large bandwidth increase. In this scheme, multiple pulses per frame are used, with the pulse positions being determined by the original PCM word. The main concern of this thesis is a full and detailed investigation of an Optical MPPM link operating over a dispersive optical channel. As the analysis of any (X/Y) multiple PPM system, in which X denotes the number of data slots and Y the number of pulses, is extremely time-consuming, a novel automated solution was designed to predict the equivalent PCM error rates of specific sequences and simplify the task. An original mathematical formulation is developed using the Maximum Likelihood Sequence Detection (MLSD) scheme. Using the equivalent PCM error rates of specific sequences generated from software, a full simulation of an MPPM optical link can be produced and the results show the effectiveness of the MPPM format over PPM. A measure of coding quality is proposed that accounts for efficiency of coding and bandwidth expansion. Original results are presented for a (12/Y) MPPM system, considered as very efficient and examined by many authors, showing that the most efficient systems are in the middle of the family. A methodology to predict the Bit Error Rate (BER) of any MPPM system is also proposed. The results obtained confirmed the results obtained from the full mathematical analysis. The effects of linear increment, linear decrement, Gray code and random mapping of data on ther performance of a (12/Y) multiple PPM system are also examined. Simulations show that the Gray code is the most effective as it minimizes the Hamming distance between adjacent multiple PPM words. Further experiments showed that system performance can be obtained exclusively with the use of software making the analysis simpler and minimizing the time consumption. A novel algorithm is presented and results obtained using this method, agree with those obtained using a full mathematical model. Certain mappings can either enhance or degrade the final total error probability of the system and hence affect the sensitivity of the MLSD scheme. In this thesis the author also suggests a methodology of how to predict and generate an optimum or close to optimum mapping. The methodology is based on minimizing the occurrence of dominant error sequences. Detailed results show the effectiveness of this mapping routine. For the first time also, high order MPPM codes are considered for analysis. All the experiments completed for the (12/Y) MPPM system are repeated for a range of MPPM systems (with 4, 7, 15, 17, 22, 28 and 33 slots operating over a plastic optical fibre (POF) channel showing again that the most efficient systems are in the middle of the family. Close to optimum mappings are also presented for these MPPM systems. The estimated mappings were found to be far superior to the efficient Gray codes, linear coding and a series of random mappings. To measure these optimum mappings a very efficient mapping is also considered. This mapping minimises the Hamming distance between all MPPM codewords. This mapping allows repetitions of MPPM codewords and cannot be used in a MLSD scheme. Therefore, it is only used for comparisons with the (close to) optimum mappings. It is shown that the optimum mappings are close to ideal. Other correlation techniques are also considered for optimised detection in the MLSD scheme. Results obtained showed that raised cosine filtering can enhance detection.
19
Zeidler, Brandon J. "Noncoherent detection of pulse-position modulation with correlated Gaussian interference in a slowly fading two-path channel." Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2006. http://wwwlib.umi.com/cr/ucsd/fullcit?p3196544.
Full textAbstract:
Thesis (Ph. D.)--University of California, San Diego, 2006.Title from first page of PDF file (viewed February, 2006). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references (p. 248-250).
20
Fardo, Francesca. "Influence of body position, emotions, placebo and cognitive modulation on pain experience and pain-related somatosensory ERPs." Doctoral thesis, Università degli studi di Padova, 2013. http://hdl.handle.net/11577/3423020.
Full textAbstract:
The present work contributed to our understanding of the neurocognitive mechanisms underlying pain modulation through sensory, attentional, emotional and cognitive processes. We used subjective, behavioral, and electrophysiological indexes to reveal the effects of body position, emotions, placebo expectations and cognitive reappraisal on subjective pain experience and pain-related somatosensory potentials. Four studies were conducted to investigate different forms of pain modulation. Study 1 tested the hypothesis that the horizontal body position reduces pain perception and cortical pain processing. We demonstrated that the supine vs. sitting body position was associated with dampened perception of non-painful stimuli and inhibited cortical late processing (300-600 ms) of non-painful and painful stimuli, related to neural activity within frontal right regions (anterior cingulate cortex and superior frontal gyrus). Study 2 investigated gender differences in the emotional modulation of pain. Although males and females did not differ at the behavioral level and reported reduced pain ratings only during the visual perception of erotic pictures, striking gender differences emerged in the N2 and P2 potentials, elicited by painful stimuli. Males showed inhibited cortical processing of pain stimuli when viewing erotic pictures only, whereas females showed a differentiated cortical pain modulation for each emotional content took into consideration (erotic vs. sport/adventure vs. neutral vs. fear/threat vs. mutilation pictures), in particular for N2 potentials. In Study 3, we examine the role of individual beliefs on the effectiveness of a traditional and a homeopathic analgesic treatment. We utilized a deceptive paradigm, i.e., neither the participants nor the experimenters were aware that the administered treatment was an inert substance. We found that only the participants who took a treatment that was coherent with their beliefs showed a reduced cortical pain processing, indicated by dampened P2 amplitudes. Finally, Study 4 demonstrated that healthy participants are able to modify their pain experience using an imaginary-based reappraisal strategy. Perceived pain intensity and unpleasantness were either reduced or enhanced with respect to a neutral condition, and an effective pain inhibition was associated with increased N2 and decreased P2 amplitudesIl presente lavoro di ricerca ha contribuito alla comprensione dei meccanismi neurocognitivi sottostanti alla modulazione del dolore da parte di processi sensoriali, attenzionali, emozionali e cognitivi. Abbiamo preso in considerazione indici soggettivi, comportamentali ed elettrofisiologici per rilevare gli effetti della posizione del corpo, delle emozioni, delle aspettative legate al placebo, e del reappraisal cognitivo sull’esperienza soggettiva del dolore e sui potenziali somatosensoriali dolore-relati. Quattro studi sono stati condotti per indagare differenti tipologie di modulazione del dolore. Lo Studio 1 ha testato l’ipotesi che la posizione orizzontale del corpo riduca la percezione e l’elaborazione corticale del dolore. Abbiamo dimostrato che la posizione del corpo supina vs. seduta era associata ad una diminuita percezione di stimoli non dolorosi e ad una inibita elaborazione corticale tardiva (300-600) di stimoli dolorosi e non dolorosi, relata ad attività neurale in regioni frontali destre (corteccia cingolata anteriore e giro frontale superiore). Lo Studio 2 ha indagato le differenze di genere nella modulazione emozionale del dolore. Sebbene maschi e femmine non differissero a livello comportamentale e mostrassero ridotti punteggi di dolore solamente durante la visione di immagini erotiche, delle notevoli differenze di genere sono emerse nei potenziali N2 e P2 elicitati da stimoli dolorosi. I maschi avevano mostrato una inibita elaborazione corticale del dolore solamente durante la visione di immagini erotiche, mentre le femmine hanno mostrato una modulazione corticale del dolore diversificata per ogni contenuto emozionale preso in considerazione (immagine erotiche vs. sport/avventura vs. neutre vs. paura/minaccia vs. mutilazione), in particolare per la N2. Nello Studio 3, abbiamo esaminato il ruolo delle credenze individuali nell’efficacia di un trattamento analgesico tradizionale e di uno omeopatico. Abbiamo utilizzato un paradigma decettivo, i.e., né i partecipanti, né le sperimentatrici erano a conoscenza che il trattamento somministrato era una sostanza inerte. Abbiamo trovato che solamente i partecipanti che assumevano un trattamento che era coerente con le loro credenze mostravano una ridotta elaborazione corticale del dolore, indicata da diminuite ampiezze della P2. Infine, lo Studio 4 ha dimostrato che i partecipanti sani sono in grado di modificare la propria esperienza del dolore, utilizzando una strategia di reappraisal cognitiva che fa uso di immagini mentali. L’intensità di dolore percepita era o diminuita o aumentata rispetto ad una condizione neutra e un’efficace inibizione del dolore era associata ad incrementate ampiezze N2 e diminuite ampiezze P2
21
Khan, Hamid. "Optimised space vector modulation for variable speed drives." Phd thesis, Université Blaise Pascal - Clermont-Ferrand II, 2012. http://tel.archives-ouvertes.fr/tel-00999475.
Full textAbstract:
The dissertation documents research work carried out on Pulse Width Modulation (PWM) strategies for hard switched Voltage Source Inverters (VSI) for variable speed electric drives. This research is aimed at Hybrid Electric Vehicles (HEV). PWM is at the heart of all variable speed electric drives; they have a huge influence on the overall performance of the system and may also help eventually give us an extra degree of freedom in the possibility to rethink the inverter design including the re-dimensioning of the inverter components.HEVs tend to cost more than conventional internal combustion engine (ICE) vehicles as they have to incorporate two traction systems, which is the major discouraging factor for consumers and in turn for manufacturers. The two traction system increases the maintenance cost of the car as well. In addition the electric drives not only cost extra money but space too, which is already scarce with an ICE under the hood. An all-electric car is not yet a viable idea as the batteries have very low energy density compared with petrol or diesel and take considerable time to charge. One solution could be to use bigger battery packs but these add substantially to the price and weight of the vehicle and are not economically viable. To avoid raising the cost of such vehicles to unreasonably high amounts, autonomy has to be compromised. However hybrid vehicles are an important step forward in the transition toward all-electric cars while research on better batteries evolves. The objective of this research is to make electric drives suitable for HEVs i.e. lighter, more compact and more efficient -- requiring less maintenance and eventually at lower cost so that the advantages, such as low emissions and better fuel efficiency, would out-weigh a little extra cost for these cars. The electrical energy source in a vehicle is a battery, a DC Voltage source, and the traction motor is generally an AC motor owing to the various advantages it offers over a DC motor. Hence the need for a VSI, which is used to transform the DC voltage into AC voltage of desired amplitude and frequency. Pulse width modulation techniques are used to control VSI to ensure that the required/calculated voltage is fed to the machine, to produce the desired torque/speed. PWM techniques are essentially open loop systems where no feedback is used and the instantaneous values differ from the required voltage, however the same average values are obtained. Pulse width modulated techniques produce a low frequency signal (desired average value of the switched voltage) also called the fundamental component, along with unwanted high frequency harmonics linked to the carrier signal frequency or the PWM period. In modern cars we see more and more mechanical loads driven by electricity through digital processors. It is very important to eliminate the risk of electromagnetic interference between these systems to avoid failure or malfunction. Hence these unwanted harmonics have to be filtered so that they do not affect the electronic control unit or other susceptible components placed in the vicinity. Randomised modulation techniques (RPWM) are used to dither these harmonics at the switching frequency and its multiple. In this thesis a random modulator based on space vector modulation is presented which has additional advantages of SVM. Another EMI problem linked to PWM techniques is that they produce common mode voltages in the load. For electric machines, common mode voltage produces shaft voltage which in turn provokes dielectric stress on the motor bearings, its lubricant and hence the possibility of generating bearing currents in the machine that can be fatal for the machine. To reduce the common mode voltage a space vector modulation strategy is developed based on intelligent placement of zero vectors. (...)
22
Mostafa, Kamrunnasim. "Theoretical analyses and practical implementation of duobinary pulse position modulation using Mathcad, VHDL, FPGA and purpose-built transceiver." Thesis, University of Huddersfield, 2015. http://eprints.hud.ac.uk/id/eprint/30185/.
Full textAbstract:
Duobinary pulse-position modulation (PPM), a novel channel coding scheme, has been proposed in this thesis as an alternative method of improving bandwidth utilisation efficiency and sensitivity over existing coding schemes such as digital PPM, dicode PPM, multiple PPM and offset PPM while operating over slightly or highly dispersive graded-index (GI) plastic optical fibre (POF) channels of limited bandwidth. Theoretical investigation based on simulations of mathematical models with maximum likelihood sequence detection (MLSD) at 1 Gbps on-off keying (OOK) data shows that duobinary PPM significantly outperforms optimised digital PPM at low fibre bandwidths by 8.7 dB while only operating at twice the original pulse code modulation (PCM) data rate. It has also been shown at high fibre bandwidth duobinary PPM gives a sensitivity of -42.2 dBm which is favourably comparable to digital PPM seven-level coding sensitivity of -44.1 dBm. Results presented in the thesis also demonstrate that at very low normalised fibre bandwidths (below 1 and down to 0.43) duobinary PPM outperforms dicode PPM by 1.2 dB requiring 27 x 103 photons per pulse compared to 40.3 x 103 required by Dicode PPM. Due to the use of MLSD at low bandwidths, wrong-slot errors are completely eliminated, and the effect of erasure and false-alarm errors are significantly reduced thus resulting in significantly improved sensitivity. Successful VHSIC hardware description language (VHDL) and field programmable gate array (FPGA) implementation of duobinary PPM coder, decoder and MLSD as a single system has been presented in the thesis. An FPGA embedded bit error rate (BER) test device has also been implemented for sensitivity measurements purposes and all the designs have been tested successfully with back-to-back testing. A purpose-built VCSEL 850 nm wavelength based transceiver system has been designed and successful functional tests have been carried out. Maximum operational data rate of the transceiver is currently 622 Mbps to match the maximum operating frequency of the FPGA, however, it has the capability to operate up to 3.2 Gbps. Further work on receiver characterisation and slot and frame synchronisation of duobinary PPM is required. All the results and analyses indicate that duobinary PPM is an ideal alternative to be considered for highly dispersive optical channels, and performance evaluation for higher bandwidths also favourably compares to existing coding schemes with only twice the expansion of original PCM data rate.
23
Ben, Sassi Marwen. "Contribution à la mesure temporelle et à la simulation en équilibrage harmonique de la stabilité d’impulsion à impulsion de transistors en technologie GaN." Thesis, Limoges, 2021. http://www.theses.fr/2021LIMO0018.
Full textAbstract:
Ce travail de thèse a permis de décrire, pour la première fois à notre connaissance, une comparaison des performances Pulse à Pulse (P2P) d'un HEMTAlGaN/GaN obtenue, expérimentalement d'une part grâce à un système de caractérisation entièrement étalonné et d'autre part, grâce à une simulation Harmonic Balance (HB) 2tons d'un modèle fonderie du transistor. Les mesures et les simulations HB permettent l'extraction simultanée et cohérente, d'une part, des enveloppes complexes des tensions et courants hyperfréquences (RF) et, d'autre part, du courant de drain Basse Fréquence (BF) généré par les non-linéarités des composants mesurés ou de leurs modèles électrothermiques simulés. Les enveloppes complexes de tension et de courant aux deux ports des dispositifs sous test (DST) et de la tension et du courant (BF) de drain ont été simultanément mesurées/simulées avec une rafale radar irrégulière périodique composée d'impulsions transitoires ultra courtes et en utilisant les mêmes rafales radar dont, la largeur d’impulsion t et les temps de montée/descente ont été modifiés. L’originalité majeure de ce travail réside dans le fait que les formes d'onde RF générées dans le domaine temporel utilisées par les sources du banc de test ou celles des simulation sont été corrigées pour réduire considérablement les phénomènes de Gibbs.Les facteurs de Lanczos/Fejér ont été implémentés dans des simulateurs. En revanche, à notre connaissance, c'est la première fois qu'ils sont directement utilisés pour générer un signal utile dans un système de caractérisation micro-ondes et dans une simulation HB 2tonsThis work describes, for the first time to our knowledge, a comparison of Pulse to Pulse (P2P) stabilities of an AlGaN/GaN HEMT experimentally extracted thanks to an on-wafer fully calibrated characterization system and on the other hand, from a Harmonic Balance (HB) two-tone simulation of a foundry-based model of the transistor. For the first time, Lanczos and Fejér factors are experimentally implemented in the time-domain characterization system in order to reduce the Gibbs phenomen on effects and to perform causal measurements.Thanks to these two tools, the complex envelopes of the microwave (RF) voltages and currents and the Low-Frequency (LF) drain current have been measured/simulated. The complex RF voltage/current envelopes at both ports of the DUT and the LF drain voltage/current have been simultaneously measured/simulated using a periodic irregular radar burst.The P2P stability criterion has been calculated, in this work, using two mathematical expressions (RMS/ET).These two methods are based on the use of the amplitude/phase or the real/imaginary of the measured/simulated (HB 2tone) complex envelopes of the RF output voltage. Ultra-short transient pulses(13ns) have been used. Simulation preliminary results are processing. They will constitute a solid preparation for the future work
24
Kirat, Régis. "Modélisation et commande en position d'un vérin pneumatique contrôle par un ensemble de 4 (quatre) électrovannes pilotées en modulation de largeur différentielle." Lyon, INSA, 1992. http://www.theses.fr/1992ISAL0100.
Full textAbstract:
Le travail exposé dans ce mémoire a pour objectif l'étude en simulation et expérimentale des possibilités d'application de la commande par retour d'état au positionnement d'un vérin pneumatique contrôlé par un ensemble de quatre électrovannes tout-ou-rien pilotées en modulation de largeur différentielle. Le premier chapitre est consacré à l'examen d'un certain nombre de solutions pneumatiques et hydrauliques, tant en terme de composant qu'en terme de commande de type M. L. I. Ou M. L. D. Le deuxième chapitre porte sur l'étude théorique et expérimentale du modulateur électropneumatique formé de 4 électrovannes disposées en pont de Wheatstone et pilotées en M. L. D. Les essais nécessaires à la caractérisation statique et dynamique à la fois d'une électrovanne et d'un demi pont sont définis dans le but de répondre aux besoins de la simulation et de la synthèse de la commande. Les différents modèles non linéaires et linéarisés nécessaires pour la simulation et la synthèse de la commande en position sont établis dans le troisième chapitre en prenant pour point de départ une représentation bond graphs. Ce chapitre comporte une étude détaillée de la méthodologie retenue pour effectuer la synthèse de la commande par retour d'état et d'un exemple d'application de cette méthodologie dans le cas d'un axe de robot. Dans le quatrième chapitre ont étés regroupés les résultats expérimentaux relatifs à l'axe de robot considéré tant du point de vue dynamique que statique. Une comparaison entre les résultats expérimentaux et et simulés permet de juger de la validité de la démarche retenueThe aim of this thesis is to study the simulation and experimentation related to the possibility of applying a state feedback position control to a pneumatic cylinder operated by means of a set of four differential pulse-width modulated on-off valves. In the first chapter, we examine a certain number of pneumatic and hydraulic solutions from the point of view of component design as well as from the point of view of PWM or DPWM control. Th. E second chapter deals with theoretical and experimental study of the electro-pneumatic modulator. This device consists of a set of four DPWM electro valves fitted in a Wheatstone bridge arrangement. Necessary static and dynamic characterization of both a single electro valve and a half bridge is performed in order to meet the requirements of simulation and control synthesis. The different non-linear and linearised models needed for simulation and position control synthesis are developed in the third chapter starting with a bond graphs representation. This chapter includes a detailed study of the state feedback. Control synthesis methodology retained, as well as an example of application to the case of a robot axis. The fourth chapter brings together the experimental results connected to the robot axis considered, as rush from the dynamic point of view as from the static one. Comparing experimental and simulation results allows us to judge the validity of the adopted approach
25
Mosa, H. "Enhancing the bit error rate performance of ultra wideband systems using time-hopping pulse position modulation in multiple access environments." Thesis, University of Salford, 2017. http://usir.salford.ac.uk/44272/.
Full textAbstract:
Ultra-Wide Band (UWB) technology is one of the possible solutions for future short-range indoor data communication with uniquely attractive features inviting major advances in wireless communications, networking, radar, imaging, and positioning systems. A major challenge when designing UWB systems is choosing a suitable modulation technique. Data rate, transceiver complexity, and BER performance of the transmitted signal are all related to the employed modulation scheme. Several classical modulation schemes can be used to create UWB signals, some are more efficient than others. These schemes are namely, Pulse Position Modulation (PPM), Pulse Amplitude Modulation (PAM), Binary Phase Shift Keying (BPSK), and On-Off Keying (OOK) are reviewed. In the thesis, the performance of PPM system, combined with Time Hopping Spread Spectrum (THSS) multiple access technique is evaluated in an asynchronous multiple access free space environment. The multiple access interference is first assumed to be a zero mean Gaussian random process to simulate the scenario of a multi user environment. An exact BER calculation is then evaluated based on the characteristic function (CF) method, for Time Hopping-Pulse Position Modulation Ultra Wide Band (TH-PPM UWB) systems with multiple access interference (MAI) in AWGN environment. The resulting analytical expression is then used to assess the accuracy of the MAI Gaussian Approximation (GA) first assumed. The GA is shown to be inaccurate for predicting BERs for medium and large signal-to-noise ratio (SNR) values. Furthermore, the analysis of TH-PPM system is further extended to evaluate the influence of changing and optimising some of the system or signal parameters. It can be shown how the system is greatly sensitive to variations in some signal parameters, like the pulse shape, the time-shift parameter associated with PPM, and the pulse length. In addition, the system performance can be greatly improved by optimising other system parameters like the number of pulses per bit, Ns, and the number of time slots per frame, Nh. All these evaluation are addressed through numerical examples. Then, we can say that, by improving signal or system parameters, the BER performance of the system is greatly enhanced. This is achieved without imposing exact complexity to the transceiver and with moderate computational calculations.
26
Mansouri, Omar. "Sur l'autopilotage à capteur statique de position d'actionneur électromagnétique direct en milieux confinés : & l'amélioration de la qualité de tension d'onduleur triphasé." Versailles-St Quentin en Yvelines, 2007. http://www.theses.fr/2007VERS0017.
Full textAbstract:
This research work can be subdivided into two parts :the first part deals with the study and implementation of a sensorless self control loop of a direct-acting electromagnetic actuator used in confined media. The objective is to eliminate the whole kinematic linkage so as the torque is directly applied to the mechanical load through a nonmagnetic confining case. The industrial applications sought may include all industries requiring a controlled surrounding where, one should either protect human beings from material (radioactive), or protect material from human operators (phamaceutical, cosmetic, agri-food industry,. . . ). This actuator must be adapted to an already existing radioactive waste processing system. To optimize the electromagnetic torque, to control the speed and avoid uncoupling, we have designed a new static position sensor. This inductive sensor is made up of three windings. An electronic circuit has been implemented for sensor signals conditionning, inverter control and motor start. The static position sensor This electronic circuit is fed from the static position sensor. The second part deals with the study and practical implementation of a three-phase inverter using pre-calculated switching angles. The objective is to optimize both the harmonic distortion rate and the number of switching actions per period so as to minimize the power losses with the switches and obtain a good quality inverter output voltage. Two methods have been proposed. In the first one, the inverter directly supplies the load. The switching angles are directly determined so as to eliminate most of succesive low ranked harmonics. We have proposed two techniques for switching angles calculation to control the inverter. In the second method, we used a passive LC type filter between the inverter and the three-phase load. The objective sought is to enhance more the quality of the output voltage by eliminationg more harmonics withiout increasing stress on the power electronic switches. The filter has been designed so as to optimize perfomance and avoid harmonics amplification. This method allows to use polarized capitors. At last, but not leaset, we have proposed a novel three-phase inverter model that allows using polarized capacitors. This entire achived work and results obtained in simulation, using Matlab Simulink, have been experimetally implemented through experimental set-up designed in the laboratory, to validate the obtained results. The obtained results show a mechanical performance increase of the actuator and a substantial reduction of the harmonic rate at the inverter outputCette thèse est composée de deux volets. Le premier volet est consacré à l’étude et la réalisation d’une boucle d’autopilotage sans capteur mécanique d’un actionneur électromagnétique direct appliqué aux milieux confinés. Le but est de supprimer toute la chaîne cinématique afin de transmettre directement le couple à la charge mécanique au travers d’une paroi amagnétique de confinement. Les applications visées concernent toutes les industries à ambiance contrôlée où on doit soit protéger l’homme de la matière (nucléaire), soit protéger la matière de l’homme (pharmaceutique, cosmétique, agroalimentaire). Cet actionneur doit être adapté à une situation d’exploitation préexistante en traitement de déchets radioactifs. Afin d’optimiser le couple électromagnétique transmis, de contrôler la vitesse et d’éviter le décrochage, nous avons mis au point un nouveau capteur statique de position. Ce capteur inductif est composé de trois enroulements disposés dans la partie naturelle. Un circuit électronique a été mis au point pour la mise en forme des signaux nécessaires à la commande de l’onduleur et à la régulation de vitesse à couple maximale. Le signal d’entrée de ce circuit est issu du capteur statique de position. Le second volet de cette thèse consiste en l’étude théorique et la validation expérimentale d’un onduleur de tension à angles de commutations pré-calculés. Le but est d’optimiser simultanément le taux d’harmoniques et le nombre de commutations par période, en vue de limiter les pertes dans les interrupteurs de puissance tout en assurant une tension de bonne qualité. Pour cela deux méthodes ont été proposées. Dans la première méthode, l’onduleur alimente directement la charge. Les angles de commutations sont pré-calculés dans le but d’annuler le maximum d’harmoniques de rangs faibles et successifs. Nous avons proposés deux techniques de calcul des angles de commutations pour la commande de l’onduleur. Dans la seconde méthode, nous proposons d’insérer un filtre passif de type LC entre l’onduleur et la charge triphasée. L’objectif visé est d’augmenter encore plus la qualité de la tension de sortie en éliminant les harmoniques restants, sans augmenter les contraintes dans les composants semi-conducteurs de puissance. La conception de ce filtre a été aussi étudiée afin d’optimiser son efficacité et d’éviter l’amplification des harmoniques. Cette méthode offre aussi la possibilité de l’utilisation de condensateurs polarisés dont la capacité volumique est élevée. Tous les travaux cités ci-dessus ont été vérifiés en premier lieu par simulation sous la plate forme logicielle MATLAB Simulink. Ensuite, ils ont été validés expérimentalement au moyen de support que nous avons mis au point au sein du Laboratoire. Les résultats obtenus montrent une augmentation importante des performances électrique et mécanique de l’actionneur et une réduction significative du taux d’harmoniques en sortie de l’onduleur triphasé
27
Videt, Arnaud. "Variateur de vitesse à impact électromagnétique réduit : onduleur multiniveaux et nouvelles stratégies de modulation." Phd thesis, Ecole Centrale de Lille, 2008. http://tel.archives-ouvertes.fr/tel-00365461.
Full textAbstract:
Parmi les convertisseurs d'électronique de puissance, les variateurs de vitesse utilisés pour l'alimentation des machines électriques sont source de perturbations électromagnétiques à haute fréquence telles que les courants de mode commun et les surtensions aux bornes des moteurs. Le travail porte sur la réduction de ces perturbations par l'emploi d'un convertisseur multiniveaux associé à de nouvelles lois de commande rapprochée. Après un état de l'art des méthodes d'atténuation existantes, l'onduleur à trois niveaux de type neutral-point-clamped (NPC) est retenu comme structure de conversion continu-alternatif et une nouvelle stratégie de modulation de largeur d'impulsion (MLI) est développée en vue de réduire les courants de mode commun générés par l'onduleur. Les phénomènes entrant en jeu dans les commutations des interrupteurs de puissance sont analysés et modélisés afin d'établir des contraintes de commande permettant de maximiser les performances de la MLI proposée. Parallèlement, l'utilisation de câbles longs entre le variateur et la machine soulève une contrepartie vis-à-vis des surtensions moteur qui est maîtrisée par l'exploitation adéquate des degrés de liberté de la nouvelle MLI. Enfin, la problématique de régulation du point milieu capacitif du bus continu est abordée. La stratégie proposée est implantée expérimentalement par l'intermédiaire d'une modulation naturelle par porteuses, et les résultats de mesure montrent un gain de cinq décibels sur les courants de mode commun par rapport aux stratégies classiques tout en limitant les surtensions générées aux bornes du moteur et en assurant l'équilibrage du bus continu.
28
Xi-Hua, Li. "A NEW DATA PROCESSING TECHNIQUE OF PPM/PPK WITHOUT THE REFERENCE PULSE." International Foundation for Telemetering, 1990. http://hdl.handle.net/10150/613478.
Full textAbstract:
International Telemetering Conference Proceedings / October 29-November 02, 1990 / Riviera Hotel and Convention Center, Las Vegas, NevadaThis paper describes the technical principle that signals conversion, data-processing and data storage are directly carried out without filling up with the reference pulse for PPM and PPK (pulse position keying). By means of analysis for typical frame structure of PPM/PPK signals, a variety of math models of signal time relationship of the system were found, and based on this, a engineering way and a principle block diagram for signals conversion, data processing and data storage were given out.
29
Javahiraly, Nicolas. "Méthode d'analyse optique du module de rigidité. Application à un capteurs photonique de position angulaire et de couple à modulation d'amplitude et de polarisation." Université Louis Pasteur (Strasbourg) (1971-2008), 2002. http://www.theses.fr/2002STR13092.
Full textAbstract:
Nous présentons le principe, le concept et le développement technologique de deux types de capteurs : un capteur de position angulaire à fibre optique basé sur les phénomènes de couplage de modes, et un capteur de couple photonique basé sur la modulation de la polarisation. Après une présentation de l'état de l'art en matière de mesure du couple et de position angulaire, nous analysons la propagation de la lumière dans les fibres optiques en considérant ses aspects électromagnétiques et opto-géométriques, applicables aux capteurs à modulation de polarisation en développant le phénomène de polarisation et aux capteurs à modulation d'amplitude en développant le couplage de modes. Nous avons réalisé l'étude théorique et expérimentale des réponses du capteur de couple et position angulaire en fonction de la nature et de la géométrie du matériau le constituant. Nous obtenons expérimentalement pour le capteur de couple, des sensibilités comprises entre 2,233. 10-3 et 1,067 ʿ/N. M et des raideurs comprises entre 5,91 et 448,01 N. M/ʿ suivant la nature et la géométrie du matériau utilisé. La comparaison entre les valeurs théoriques et expérimentales donne un écart maximum de 1,68 à 3,4%. Nous avons testé la répétabilité du capteur de couple présentant un arbre creux en Acier de section carrée, de longueur 150mm. Un écart maximum de ±2,57%a été obtenu. L'influence des variations en Température pour DT=130ʿC donne une augmentation de 7% par rapport à la théorie. Enfin, en utilisant un dispositif expérimental pour obtenir un signal de référence, nous avons obtenu un écart maximum de la sensibilité et de la raideur de 0,59% par rapport à la théorie. Par conséquent, nous minimisons les fluctuations de la source avec le dispositif de référenceWe propose the principle, the concept and the technological development of two types of sensors: on fiber optic angular position sensor based on the modes coupling and a photonic torque sensor based on the polarization modulation. After a state of art concerning the torque and the angular sensor, we analyze the light propagation in the fiber optic in an electromagnetic and opto-geometrical way applicable to the sensor. We have analyzed the theoretical and the experimental responses of the sensors as a function of the material nature and its geometry. We obtained experimentally, for the torque sensor, a sensitivity between 2,233. 10-3 and 1,067 ʿ/N. M and a stiffness between 5,91 and 448,01 N. M/ʿ. The comparison between the theoretical and the experimental results gives a maximum difference between 1,68% and 3,4%. We have tested the Temperature fluctuations influence for DT=130ʿC and the results gave 7% of difference with the theory. By using an experimental set up to obtain a reference signal, we obtained a 0,59% maximum difference for the sensitivity and the stiffness. So, we minimize the source fluctuations with this reference set up
30
Tabaa, Mohamed. "Conception d'un système de transmission ultra-large bande par impulsions orthogonales." Thesis, Université de Lorraine, 2014. http://www.theses.fr/2014LORR0375/document.
Full textAbstract:
Dans cette thèse, nous proposons une méthodologie de conception d’architectures de communication dédiées aux réseaux de capteurs basées sur la technique de radio impulsionnelle pour les transmissions ultralarge bande (ULB). La technique impulsionnelle proposée ici repose sur la modulation de forme d’impulsion. L’approche de conception architecturale présentée dans cette thèse se focalise plus particulièrement sur la forme des impulsions et leur génération, qui revêt un intérêt majeur puisqu’elle constitue le support de l’information échangée. L’étude sur le choix de la forme d’impulsion nous a conduit à proposer deux architectures différentes. Une première architecture repose sur les polynômes orthogonaux, et plus particulièrement sur les polynômes d’Hermite, pour la génération des impulsions, et sur une architecture de corrélation pour la détection et la reconnaissance des trains d’impulsions transmis. La deuxième architecture est basée sur la transformée en paquets d’ondelettes discrète et peut être exploitée selon deux modes d’utilisation différents, mono et multiutilisateurs. L’utilisation d’une architecture de synthèse à l’émission et d’analyse à la réception ouvre une nouvelle orientation pour les communications numériques, permettant à la transformée en ondelettes d’assurer à la fois la génération des impulsions à l’émission et leur reconnaissance à la réception. Un intérêt immédiat de la technique proposée permet notamment de faciliter l’accès multiutilisateurs au canal ultralarge bande, et d’autoriser des communications simultanées (Many-to-one, des nœuds vers le puits) ou du broadcast (One-to-many, du puits vers les nœuds) sans surcharger la couche MAC. L’architecture proposée s’inscrit donc à l’interface des couches PHY et MAC et permet de relâcher les contraintes de conception spécifiques à ces couchesIn this thesis, we propose a design methodology for communication architectures dedicated to wireless sensor network based on impulse radio techniques for UWB communications. The impulse technique proposed in this work relies on pulse shape modulation. The architecture design approach proposed in this thesis focuses on pulses shape and their generation, which is of major interest as it constitutes the carrier of the information exchanged. The study on the choice of pulse shape led us to propose two different architectures. The first one is based on orthogonal polynomials, more especially on the Hermite polynomials, for impulse generation, and on a correlation architecture for detection and recognition of transmitted impulses. The second architecture is based on discrete wavelet packet transform and can be used according two different modes, mono and multi-users. The use of both synthesis and analysis architectures for emitter and receiver, respectively, offers a new way for digital communications and allows the wavelet transform to ensure the impulses generation on the transmitter and their recognition on the receiver. A major interest point of the proposed technique is to facilitate the multi-users access to the ultra-wideband channel and to allow simultaneous communications (many-to-one, from the sensors to the sink) or broadcast (one-to-many, from the coordinator to the nodes) but without overloading the MAC layer. Hence, the proposed architecture is part of the interface between both PHY and MAC layers, and allows to release their specific design constraints
31
Orndorff, Aaron. "Transceiver Design for Ultra-Wideband Communications." Thesis, Virginia Tech, 2004. http://hdl.handle.net/10919/33179.
Full textAbstract:
Despite the fact ultra-wideband (UWB) technology has been around for over 30 years, there is a newfound excitement about its potential for communications. With the advantageous qualities of multipath immunity and low power spectral density, researchers are examining fundamental questions about UWB communication systems. In this work, we examine UWB communication systems paying particular attention to transmitter and receiver design.
This thesis is specifically focused on a software radio transceiver design for impulse-based UWB with the ability to transmit a raw data rate of 100 Mbps yet encompasses the adaptability of a reconfigurable digital receiver. A 500 ps wide Gaussian pulse is generated at the transmitter utilizing the fast-switching characteristics of a step recovery diode. Pulse modulation is accomplished via several stages of RF switches, filters, and amplifiers on a fully designed printed circuit board specifically manufactured for this project. Critical hardware components at the receiver consist of a bank of ADCs performing parallel sampling and an FPGA employed for data processing. Using a software radio design, various modulation schemes and digital receiver topologies are accommodated along with a vast number of algorithms for acquisition, synchronization, and data demodulation methods. Verification for the design is accomplished through transmitter hardware testing and receiver design simulation. The latter includes bit error rate testing for a variety of modulation schemes and wireless channels using a pilot-based matched filter estimation technique. Ultimately, the transceiver design demonstrates the advantages and challenges of UWB technology while boasting high data rate communication capability and providing the flexibility of a research testbed.
Master of Science
32
Šiška, Martin. "Impulzové modulace." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2013. http://www.nusl.cz/ntk/nusl-220215.
Full textAbstract:
This work deals with the analysis of pulse modulation issues, work is divided into six chapters. The first chapter of the thesis deals with pulse modulations as a whole. It explains the concept of modulation, the distinction between analog and digital modulation, and there is the basic classification of pulse modulation done. The second chapter focuses on the issue of non-quantized pulse modulation. For each modulation belonging to this group is verbally and graphically explains the principle of its activities. In the third chapter, which is similar to the second chapter, the work focuses on quantized pulse modulation. Again, each of these modulations explained its basic principle. It is also in this chapter outlines the design models in Matlab-Simulink. The fourth chapter presents calculations and tables with calculated values needed for simulations. In the fifth chapter, a comparison waveforms. It contains a discussion about the dependence of modulation on their parameters, parameters of the input signal and the sampling frequency. In the final sixth chapter deals with the early design concepts and detailed diagrams for the production of demonstration products.
33
Al, Attar Houssein. "Bidirectional Electric Vehicle Charger Control." Thesis, Ecole centrale de Nantes, 2022. http://www.theses.fr/2022ECDN0043.
Full textAbstract:
Dans cette thèse inscrite dans le cadre de la chaire Renault-Centrale Nantes, l’objectif est de concevoir des stratégies de contrôle pour améliorer les performances et le rendement du chargeur réversible du Véhicule Electrique (VE). Dans le mode décharge, le nouveau défi consiste à concevoir une stratégie de Modulation par Décalage de Phase (MDP) pour améliorer la zone de fonctionnement et le rendement du convertisseur DC-DC. La loi de commande est basée sur l’inversion de gain du convertisseur DC-DC LLC. Du point de vue coût, la contribution porte essentiellement sur la conception d’une stratégie d’optimisation pour diminuer le dimensionnement du convertisseur DC-DC LLC mais aussi d’améliorer les performances de la stratégie de Modulation par Fréquence d’Impulsion (MFI). Ensuite, un développement d’un modèle grand signal du convertisseur LLC basé sur la stratégie MDP est élaboré. La contribution principale consiste à implémenter des stratégies du contrôle robuste, telles que la commande sans modèle et la commande adaptive super twisting, combinées avec la stratégie MDP. D’autre part, l’apport principal conduit à fournir une stratégie de contrôle hybride du chargeur afin de réguler la tension du bus DC dans les zones de saturation du convertisseur DC-DC. Enfin, une nouvelle topologie d’un chargeur VE avec la structure DAB est étudiée. Une stratégie de contrôle en cascade est proposée pour régler le bus DC et le courant réseau. Différentes stratégies de modulation, telles que les modulations par décalage d’un ou de deux déphasages, sont étudiées. Des résultats de simulation de modèles de chargeurs réels sont présentés afin de mettre en évidence l’efficacité des stratégies de contrôle proposéesIn this thesis, part of the chair Renault/Centrale Nantes, the aim is to design control strategies to improve the performance and efficiency of the bidirectional charger of the Electric Vehicle (EV). In the discharging mode, the new challenge is to design a Phase Shift Modulation (PSM) strategy to improve the operating zone and efficiency of the DC-DC converter. The control law is based on the DC-DC LLC gaininversion. In terms of cost, the contribution is mainly about the design of an optimization strategy, not only to reduce the sizing of the DC-DC LLC converter, but also to improve the performance of the Pulse Frequency Modulation (PFM) strategy. Then, a large signal model of the LLC converter based on the PSM strategy is developed. The main contribution consists of implementing robust control strategies, such as model-free control and adaptive super twisting control, combined with the PSM strategy. On the other hand, the key contribution leads to provide a hybrid control strategy of the charger in order to be able to regulate the DC bus voltage in the saturation zones of the DC-DCconverter. Finally, a new topology of an EV charger with the DAB structure is studied. A backstepping control strategy is proposed to regulate the DC bus voltage and the grid current. Different modulation strategies, such as single and dual phase shift modulation,are studied. Simulation results of real charger models are presented in order to highlight the effectiveness of the proposed control strategies
34
Onunkwo, Uzoma Anaso. "Timing Jitter in Ultra-Wideband (UWB) Systems." Diss., Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/10465.
Full textAbstract:
Timing offsets result from the use of real clocks that are non-ideal in sampling intervals. These offsets also known as timing jitter were shown to degrade the performance of the two forms of UWB systems impulse radio and orthogonal frequency division multiplexing (OFDM)-based UWB. It was shown that for impulse radio, timing jitter distorts the correlation property of the transmitted signal and the resulting performance loss is proportional to the root-mean-square (RMS) value of the timing jitter. For the OFDM-based UWB, timing jitter introduced inter-channel interference (ICI) and the performance loss was dependent on the product of the bandwidth and the RMS of the timing jitter. A number of techniques were proposed for mitigating the performance degradation in each form of UWB. Specifically, for impulse radio, the methods of pulse shaping and sample averaging were provided, whereas for OFDM-based UWB, oversampling and adaptive modulation were given. Through analysis and simulation, it was shown that substantial gain in signal power-to-noise ratio can be achieved using these jitter-reduction methods.
35
Kolli, Abdelfatah. "Analyse d’une architecture de puissance dédiée aux modes traction–recharge dans un véhicule électrique. Optimisation de la commande et fonctionnement en mode dégradé." Thesis, Paris 11, 2013. http://www.theses.fr/2013PA112316/document.
Full textAbstract:
La problématique de recherche abordée dans ce mémoire de thèse découle de l’étude approfondie d’une association convertisseur-machine dédiée aux modes traction et recharge d’un véhicule électrique. Il s’agit d’un onduleur triphasé constitué de trois onduleurs monophasés connectés à une machine triphasée à phases indépendantes.Dans le chapitre II, une étude comparative entre deux solutions industrielles montre que l’architecture étudiée offre des caractéristiques compétitives notamment en termes de rendement global du convertisseur, performances mécaniques, et surface de silicium nécessaire.Par ailleurs, outre la possibilité de mutualiser les trois fonctions du véhicule que sont la traction, la recharge (rapide ou lente) et l’assistance du réseau électrique, cette topologie offre plusieurs atouts : des possibilités variées d’alimentation et donc un potentiel intéressant de reconfiguration en marche dégradée. La thématique abordée dans les chapitres III et IV est donc centrée sur l’optimisation des stratégies de contrôle de cette structure vis-à-vis de deux types de défauts : les imperfections intrinsèques du système d’une part et les défaillances accidentelles d’autre part.Dans un premier temps, un travail approfondi sur les méthodes de modulation de largeur d’impulsion a permis de synthétiser une stratégie offrant une faible sensibilité vis-à-vis des imperfections de la commande et de la non-linéarité du convertisseur. Dans un second temps, il a été montré qu’en cas de défaillance d’un composant à semi-conducteur, il était obligatoire de recourir à la reconfiguration matérielle de la topologie. L’architecture permettant la continuité de service a été étudiée du point de vue de sa commande. Son analyse nous a amenés à proposer une structure de contrôle basée sur des solutions automatiques simples et efficaces. Finalement, le principe du fonctionnement en marche dégradée a été étendu au fonctionnement normal dans le but d’en améliorer le rendement sur cycleThis Ph.D. thesis focuses on a novel combination of a frequency converter and an electric machine specially dedicated to traction drive and battery recharging modes of an electric vehicle (EV). This power architecture is composed of a six legs voltage inverter connected to a three-phase open-end winding machine. Chapter II details a quantitative comparison between two industrial power architectures and concludes that the SOFRACI powertrain is a competitive solution in terms of power converter efficiency, drive mechanical performances, and required silicon area.This architecture offers the attractive possibility of combining three important functions: traction and braking, battery charging and connecting the energy storage to a smart grid. In addition, this topology offers several advantages such as various motor feeding possibilities and a high degree of reconfiguration in degraded operating mode. The third and fourth chapters of this thesis concern the optimization of control strategies with regard to two types of faults: firstly the inherent imperfections in the converter itself (non modeled non-linearity and ineffective synchronization of control values) and secondly accidental failures. In the first case, an analysis of the pulse width modulation (PWM) methods enables the creation of a PWM strategy with a very low sensitivity to PWM uncertainties and the non-linear behavior of the power converter.In the second case, in the event of a faulty semiconductor device, it is shown that a hardware reconfiguration is required to enable an emergency traction mode. The sustainability of the traction mode is then examined with respect to the control strategy. This analysis leads to an innovative control structure based on basic and easy to implement solutions. Finally, the degraded mode operation principles have been extended to normal mode operation for the purpose of enhancing the cycle efficiency
36
Spittel, Daniel, Jan Poppe, Christian Meerbach, Christoph Ziegler, Stephen G. Hickey, and Alexander Eychmüller. "Absolute Energy Level Positions in CdSe Nanostructures from Potential-Modulated Absorption Spectroscopy (EMAS)." American Chemical Society, 2017. https://tud.qucosa.de/id/qucosa%3A33353.
Full textAbstract:
Semiconductor nanostructures such as CdSe quantum dots and colloidal nanoplatelets exhibit remarkable optical properties, making them interesting for applications in optoelectronics and photocatalysis. For both areas of application a detailed understanding of the electronic structure is essential to achieve highly efficient devices. The electronic structure can be probed using the fact that optical properties of semiconductor nanoparticles are found to be extremely sensitive to the presence of excess charges that can for instance be generated by means of an electrochemical charge transfer via an electrode. Here we present the use of EMAS as a versatile spectroelectrochemical method to obtain absolute band edge positions of CdSe nanostructures versus a well-defined reference electrode under ambient conditions. In this, the spectral properties of the nanoparticles are monitored with respect to an applied electrochemical potential. We developed a bleaching model that yields the lowest electronic state in the conduction band of the nanostructures. A change in the band edge positions caused by quantum confinement is shown both for CdSe quantum dots and for colloidal nanoplatelets. In the case of CdSe quantum dots these findings are in good agreement with tight binding calculations. The method presented is not limited to CdSe nanostructures but can be used as a universal tool. Hence, this technique allows the determination of absolute band edge positions of a large variety of materials used in various applications
37
Graziani, Filippo. "Modulazioni "Time-reversal" con codifiche a bassa profondità per comunicazioni ultrasoniche." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021. http://amslaurea.unibo.it/22625/.
Full textAbstract:
Nel presente elaborato viene affrontata la tematica relativa alla comunicazione mediante onde ultrasoniche guidate.
Nel dettaglio, l'attenzione viene rivolta alla propagazione delle onde di Lamb, le quali sono in grado di propagarsi su strutture molto sottili con bassa attenuazione, dando luogo alla possibilità di realizzare questo schema di comunicazione.
La tecnica "time-reversal" sfrutta le proprietà di queste onde, ovvero la focalizzazione spaziale e temporale, per portare dei picchi accentuati al ricevitore in corrispondenza dell'informazione utile.
Questa tecnica, accoppiata con la Pulse Position Modulation, consente la realizzazione di sistemi di comunicazione con più nodi sensori contemporaneamente attivi in trasmissione e uno o più nodi sensori in ricezione.
Viene inoltre considerata la possibilità di sfruttare algoritmi di quantizzazione, intesa come capacità di generazione del segnale in uscita su un numero limitato di livelli, al fine di rendere il sistema di comunicazione semplice ed economico.
Le prestazioni del sistema sono verificate mediante simulazioni, realizzate in ambiente di sviluppo Matlab.
38
Bouwer, Pieter. "Modelling, design and implementation of a small-scale, position sensorless, variable speed wind energy conversion system incorporating DTC-SVM of a PMSG drive with RLC filter." Thesis, Stellenbosch : Stellenbosch University, 2013. http://hdl.handle.net/10019.1/80242.
Full textAbstract:
Thesis (MScEng)--Stellenbosch University, 2013.Wind energy has proven to be a viable source of clean energy, and the worldwide demand is growing rapidly. Variable speed topologies, with synchronous generators and full-scale converters, are becoming more popular, and the e ective control of these systems is a current trend in wind energy research. The purpose of this study is the modelling, design, simulation and implementation of a small-scale, variable speed wind energy conversion system, incorporating the position sensorless direct torque control with space vector modulation, of a permanent magnet synchronous generator, including an RLC converter lter. Another aim is the development of a gain scheduling algorithm that facilitates the high level control of the system. Mathematical models of the combined lter-generator model, in the stationary and rotating reference frames, are presented and discussed, from which equivalent approximate transfer functions are derived for the design of the controller gains. The design of the controller gains, RLC lter components, gain scheduling concept and maximum power point tracking controller are presented. It is discovered that the RLC lter damping resistance has a signi cant e ect on the resonance frequency of the system. The system is simulated dynamically in both Simulink and the VHDL-AMS programming language. Additionally, the maximum power point tracking controller is simulated in the VHDL-AMS simulation, including a wind turbine simulator. The simulation results demonstrate good dynamic performance, as well as the variable speed operation of the system. The practical results of torque and speed controllers show satisfactory performance, and correlate well with simulated results. The detailed gain scheduling algorithm is presented and discussed. A nal test of the complete system yields satisfactory practical results, and con rms that the objectives of this thesis have been reached.
39
Pauchard, Laure-Anne. "Analyse et modulation de la réponse inflammatoire au cours de l'agression pulmonaire liée à l'infection bactérienne et à la ventilation mécanique." Thesis, Dijon, 2015. http://www.theses.fr/2015DIJOMU05/document.
Full textAbstract:
Nonobstant d’immenses progrès accomplis depuis des décennies dans la prise en charge des patients soumis à la ventilation mécanique, les pneumonies acquises sous ventilation mécanique continuent de compliquer le séjour en réanimation de près de 28% des patients recevant une assistance respiratoire invasive prolongée. Parmi les malades des unités de soins intensifs, le risque de développer une pneumonie est de 3 à 10 fois supérieur chez les intubés sous ventilation. Elle reste cependant bien souvent le seul moyen de venir en aide aux patients souffrant de graves détresses respiratoires. Il a maintenant été clairement démontré que la ventilation mécanique, en particulier lorsqu’elle est mise en place selon des stratégies dites agressives, active les cellules pulmonaires conduisant alors à une réponse pro-inflammatoire même en l’absence de pathogène. Ce phénomène est connu sous le terme de biotrauma, et serait responsable en partie des lésions induites sur le poumon par la ventilation mécanique. En quelques sortes, la ventilation mécanique prépare les cellules épithéliales pulmonaires à répondre massivement à une seconde agression pro-inflammatoire par la libération de grandes quantités de cytokines (comme l’IL-8 notamment), accentuant alors les lésions du tissu pulmonaire essentiellement par le recrutement de polynucléaires neutrophiles attirés par la sécrétion massive d’IL-8. L’immunité innée joue donc un rôle très important dans le développement du VILI. L’implication des Toll Like Récepteurs a été suggérée par plusieurs études expérimentales. Par ailleurs, la ventilation en décubitus ventral a été décrite pour avoir des effets bénéfiques sur les patients ventilés souffrant de graves lésions pulmonaires particulièrement chez ceux souffrant du syndrome de détresse respiratoire aiguë. Notre équipe s’est particulièrement intéressée au TLR2, qui reconnait les bactéries à Gram-positif, car elle a montré dans des études précédentes in vitro que l’étirement cyclique de cellules pulmonaires humaines augmentait principalement l’expression de TLR2 ainsi que la réactivité de cellules pulmonaires à des composants de la paroi de bactéries à Gram positif. Ces données ont par la suite été confirmées dans un modèle in vivo de lapins ventilés dont la réponse immune innée était stimulée par du Pam3CSK4.Dans un premier projet, nous avons évalué l’impact d’une ventilation mécanique en décubitus ventral chez des lapins avec pneumonie unilatérale à Enterobacter aerogenes soumis à la ventilation mécanique. Nos résultats montrent que le décubitus ventral peut être protecteur si l’hôte est soumis à la ventilation mécanique dans le contexte d’une pneumonie bactérienne unilatérale.Pour vérifier la pertinence de nos hypothèses sur le TLR2 dans notre modèle animal de pneumonie acquise sous ventilation mécanique, nous avons mené des expériences avec des bactéries vivantes reconnues par le TLR2 (une souche de Staphylococcus aureus résistante à la methicilline SARM). Notre étude met en évidence qu’une ventilation mécanique modérément agressive impacte sur la clairance bactérienne pulmonaire en la diminuant, aggrave les lésions sur le tissu pulmonaire et favorise une réponse inflammatoire systémique. La surexpression du TLR2 tant au niveau pulmonaire que systémique pourrait expliquer ces résultats.Le troisième projet s’est attaché à évaluer l’impact d’une thérapie aux statines dans le contexte d’une pneumonie acquise sous ventilation mécanique à SARM, conjointement traitée par le linezolide, dans notre modèle animal de lapins ventilés. Nos résultats suggèrent qu’une pré-‐exposition aux statines pourrait avoir un effet anti-inflammatoire au niveau pulmonaire et systémique dans ce modèle, qui pourrait passer par une régulation négative de l’expression de TLR2, contre-balançant les effets de l’étirement cycliqueDespite major advances since decades in the management of ventilated patients, ventilator-associated pneumonia (VAP) continues to complicate the course of approximately 28% of the patients receiving mechanical ventilation (MV). Among patients hospitalized in intensive care units, the risk of pneumonia is 3- to 10- fold increased in MV patients. However, MV is often the only way to care for critically ill patients with respiratory failure. It has now been clearly demonstrated that MV, in particular adverse ventilatory strategies could activate lung cells, thus leading to a proinflammatory response, even in the absence of pathogen. This is the biotrauma paradigm, which accounts, at least in part, for the ventilator induced lung injury (VILI). In one way, MV primes airway cells to respond massively to a second proinflammatory insult, through the subsequent release of large amounts of cytokines (as interleukin (IL)‐ 8), thus leading to additional lung injury, particularly through the recruitment of neutrophils attracted by the massive release of IL-8. Accordingly, innate immunity plays an important role in the developement of VILI. The involvement of Toll-like receptors has been suggested by several experimental studies. Ventilation in the prone position (PP) has been described to have beneficial effects on patients under MV, especially in those with lobar involvement. Our team focused particularly on the TLR2, which interacts with Gram-positive bacteria, and we have previously demonstrated in vitro that cyclic stretch of human pulmonary cells resulted in TLR2 overexpression and enhanced TLR2 reactivity to Gram-positive cell wall components. We confirmed these datas in an in vivo model of ventilated rabbits which immune response had been stimulated with Pam3CSK4. In a first project, we assessed the impact of the PP on unilateral pneumonia to Enterobacter aerogenes in rabbits subjected to MV. Our results shows that the prone position could be protective if the host is subjected to MV and unilateral bacterial pneumonia. To ensure the relevance of our hypothesis on TLR2 in our animal model of VAP, we conducted experiments using live bacteria specifically recognized by TLR2 (Methicilin resist. aureus). We demonstrate that mild-‐stretch MV impaired lung bacterial clearance, hastened tissue injury and promoted a systemic inflammatory response. Both pulmonary and peripheral blood TLR2 overexpression could account for such an impact. The third project assessed the impact of a statins therapy in the context of MRSA VAP, treated with linezolid, in our model of ventilated rabbits. Our results suggest that statin exposure prior to pneumonia provides an anti-‐inflammatory effect within the lung and the systemic compartment of rabbits with MRSA VAP. Although LNZ enhances pulmonary bacterial clearance, dampening the host systemic inflammatory response with statin could impede defense against MRSA in this compartment. It could be subsequent to enhanced antibacterial defences and improvements in lung mechanics, thereby blunting overwhelming inflammation. In the last project, in collaboration with the University of Geneva, we assessed whether mitochondrial alarmins are released during VILI and can generate lung inflammation. Our results confirmed the hypothesis made and showed indeed that alarmins are released during during cyclic stretch of human epithelial cells, as well as in BAL fluids from rabbits ventilated with an injurious ventilatory regimen. These alarmins stimulate lung cells to produce bioactive IL-‐1, and are likely to represent the proximal endogenous mediators of VILI and ARDS, released by injured pulmonary cells
40
Ferreira, Alisson da ConceiÃÃo. "Estudo numÃrico do acoplador duplo simÃtrico de fibras Ãpticas operando com PPM e PAM para obtenÃÃo de portas lÃgicas." Universidade Federal do CearÃ, 2008. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=2365.
Full textAbstract:
CoordenaÃÃo de AperfeiÃoamento de NÃvel SuperiorNeste trabalho, foram investigadas as caracterÃsticas de operaÃÃo de um Acoplador Direcional NÃo-Linear(NLDC) Duplo SimÃtrico, trabalhando com pulsos de , em duas diferentes aplicaÃÃes: ObtenÃÃo de portas lÃgicas E e OU, sob ModulaÃÃo Por PosiÃÃo de Pulsos (PPM); obtenÃÃo de portas lÃgicas E e OU, sob ModulaÃÃo Por Amplitude de Pulsos (PAM). A investigaÃÃo à realizada, atravÃs de simulaÃÃes numÃricas, utilizando-se do mÃtodo de Runge Kutta de quarta ordem. Na primeira aplicaÃÃo, à analisada a possibilidade da realizaÃÃo de operaÃÃes lÃgicas pelo Acoplador Direcional NÃo-Linear (NLDC) Duplo SimÃtrico sem perda. Considerando a operaÃÃo das portas lÃgicas, foram utilizadas as quatro possÃveis combinaÃÃes para dois pulsos, nas fibras 1 e 2, modulados pela posiÃÃo temporal (PPM) nos nÃveis lÃgicos 0 ou 1. Foram investigados os efeitos de uma variaÃÃo no parÃmetro de ajuste da modulaÃÃo PPM, ou seja, no deslocamento inicial do pulso em relaÃÃo ao pulso referencial, ou informaÃÃo nÃo modulada, e na diferenÃa de fase entre os pulsos sÃlitons fundamentais de entrada devidamente modulados. Na segunda aplicaÃÃo, o NLDC duplo simÃtrico à submetido à modulaÃÃo PAM, utilizando-se tambÃm, das quatro combinaÃÃes possÃveis para os dois pulsos, nas fibras de entrada. Foram investigados os efeitos da variaÃÃo no parÃmetro de ajuste da modulaÃÃo PAM na amplitude inicial do pulso em relaÃÃo à amplitude de referÃncia, ou sinal sem modulaÃÃo, e tambÃm observada a amplitude de saÃda modulada versus uma diferenÃa de fase entre os pulsos sÃlitons fundamentais de entrada devidamente modulados. Nas duas aplicaÃÃes foram obtidas portas lÃgicas E e OU.
In this work, the performance study of a Symmetric Dual-Core Non-Linear Directional Coupler (NLDC), working with pulses of , in two different applications have been investigated: accomplishment of logical gates AND and OR, under Pulse Position Modulation (PPM); accomplishment of logical gates AND and OR, under Pulse Amplitude Modulation (PAM). The investigation is based in a numerical simulation study, using the fourth order Runge Kutta numerical method. In the first application, the possibility of the accomplishment of logical operations by Symmetric Dual-Core Non-Linear Directional Coupler (NLDC) without loss is analyzed. Considering the operation of the logical gates, the four possible combinations for two pulses, on the input fibers, modulated by the temporal PPM in the logical levels 0 or 1, were used. The effects of a variation in the coding parameter offset of the PPM modulation, that is, in the displacement of the input pulse relative to the reference time level, was investigated. In the second application, the symmetric dual-core NLDC is submitted to PAM modulation, using the four possible combinations for two pulses on the input fibers, were used, as well. The effects of a variation in the coding parameter offset of the PAM modulation relative to the reference amplitude, was investigated. The modulated output amplitude versus a phase difference between the input pulses , was also studied. On the two applications, logical gates AND and OR was observed.
41
STALLO, COSIMO. "Wireless technologies for future multi-gigabit communications beyond 60 GHz: design issues and performance analysis for terrestrial and satellite applications." Doctoral thesis, Università degli Studi di Roma "Tor Vergata", 2010. http://hdl.handle.net/2108/1302.
Full textAbstract:
Oggigiorno la richiesta di comunicazioni wireless ad alto data rate cresce proporzionalmente alle velocità di trasferimento dati raggiungibili mediante l’uso della fibra ottica. Infatti, la tendenza ultima in materia di ricerca è quello di sviluppare sistemi che consentano a utenti mobili velocità di connessione almeno confrontabili con quello della Ethernet Wired. Lo standard GbE è ormai consolidato, mentre quello 10 GbE è disponibile dal 2002. Mentre la tecnologia in fibra ottica è in grado di fornire data rate dell’ordine di alcuni multi-gigabit/s, i costi ed i tempi per la sua messa in opera sono ancora proibitivi per alcune applicazioni. Ponti wireless troverebbero impiego nella copertura dei buchi nella rete in fibra con costi contenuti e senza azioni complesse di scavo. In questo scenario, le comunicazioni wireless ai multigigabit consentiranno di sostituire il segmento in fibra nei futuri sistemi di terza e quarta generazione, nei sistemi di antenna distribuiti, nelle applicazioni commerciali come la trasmissione di video ad alta definizione (HDTV). Le singole abitazioni così come gli interi complessi residenziali nei prossimi decenni potranno usufruire, grazie alle comunicazioni wireless ai multi gigabit, di nuovi servizi ed applicazioni. La necessità di così alto contenuto informativo dunque emergera’ sia in scenari a corto raggio che medio-lungo.
Dove una così elevata larghezza di banda necessaria per realizzare comunicazioni wireless ai multi-gigabit e’ presente senza problematiche di interferenza?
L’attenzione cade sulle EHF dove sono disponibili grandi porzioni di banda. Recentemente, si e’ mostrato grande interesse per lo sviluppo di sistemi operanti a 60 GHz per applicazioni sia indoor che outdoor, essendo in diversi paesi non licenziata. Comunque, a causa dell’elevata attenuazione dovuta al picco di assorbimento dell’ossigeno a queste frequenze, tali sistemi non sono indicati per lunghi collegamenti. Inoltre, le FCC hanno stabilito che le frequenze nello spettro tra i 70-95 GHz (quindi lontane dallo bande in cui c’è il picco massimo di assorbimento ossigeno) possano essere impiegate per uso semi-licenziato al fine di realizzare collegamenti “ultimo miglio”. D’altra parte, sopra i 60 GHz, sia su breve che corto raggio, la letteratura manca ancora di conoscenze dettagliate sulle tecniche di trasmissione, modulazione, equalizzazione piu’ opportune a queste frequenze. Il seguente lavoro di tesi ha mirato quindi ad investigare le potenzialita’ di interface radio innovative ed avanzate, come quelle basate su tecniche di trasmissione IR-UWB, per le future generazioni delle comunicazioni wireless oltre i 60 GHz per applicazioni ai Multi-gigabit/s. In particolare, questo lavoro mostra come un sistema di comunicazione del tipo IR-UWB sia sensibile alle non linearita’ circuitali tipiche a queste frequenze (Phase Noise, Timing Jitter, LNA, HPA) e confronta le prestazioni con altri schemi di trasmissione e ricezione piu’ tradizionali utilizzabili oltre i 60 GHz (in particolar modo FSK). L’obiettivo principale del lavoro è stato quello di capire vantaggi e svantaggi di un sistema di trasmissione “impulsato” nello scenario considerato rispetto, considerando appunto tutte le peculiarità propagative e tecnologiche nell’uso delle EHF.
L’utilizzo di frequenze così alte rappresenta la soluzione più adeguata per realizzare una infrastruttura cooperative per un’informazione globale al fine di garantire la cosiddetta “Connettività ai Gigabit” sfruttando collegamenti aerospaziali. Cio’ e’ mirato a fare in modo che un tale segmento radio costituisca una sorta di potenziale “dorsale in aria” per una connettività wireless globale.
Quindi, l’uso delle bande di frequenza oltre le Q/V sarà la condizione necessaria per sviluppare una rete multi-purpose, come integrazione dei sistemi terrestri e spaziali, al fine di supportare le emergenti richieste di servizio ad alto contenuto informativo.
La Banda W (75-110 GHz, rispettivamente 4 -2.7 mm) potrebbe rappresentare la risposta a queste necessità in virtù di una larghezza di banda elevata, corte lunghezze d’onda, ridotte dimensioni delle antenne, consentendo di proporre diversi innovativi servizi che necessitano di trasferimenti dati ad alta velocità.
Attualmente, purtroppo, le prestazioni di una qualunque soluzione per trasporto dati a tali frequenze attraverso la Troposfera non sono ancora note, dal momento che nessuna missione scientifica e/o per telecomunicazioni è stata realizzata, né su base sperimentale né operativamente. Quindi, missioni in banda W devono essere studiate ai fini di realizzare una prima valutazione empirica degli effetti della Troposfera sul canale radio. Quindi, l’ultima parte del mio lavoro di tesi è stato focalizzato sulla analisi e valutazione di prestazione di future missioni per l’uso della banda W anche per le comunicazioni satellitari che prevedano una linea completa di P/L operanti a tali frequenze. Lo studio e la valutazione di prestazione di missioni miranti a fornire una prima valutazione empirica degli effetti della Troposfera sul canale radio in banda W rappresenta il primo passo utile per la realizzazione di un “Sistema di Sistemi” che sia in grado di soddisfare le richieste di trasmissioni dati ad alto contenuto informativo per un grande numero di utenti finali e servizi orientati ad applicazioni specifiche.Demand for very high-speed wireless communications is proportionally growing with respect to the increasing data rates reachable by optical fibers. In fact, the emerging research trend in computer networks is to cut more and more cables and to provide mobile and nomadic users with a data rate at least comparable with that one of wired Ethernet. GbE standard is now widespread and 10 GbE standard has been available since 2002. While established and well-known fiber-optic data-transfer devices can provide multigigabit per second data rates, infrastructure costs and deployment time can be too expensive for some applications. Wireless links can be used to bridge the gaps in the fiber network and they can be deployed very rapidly, without the need for costly and complex trenching actions. Multigigabit wireless applications will include fiber segment replacement in future 3G and 4G backhauls, in distributed antenna systems, in enterprise connectivity, and in consumer-level applications, such as HDTV. Future home and building environments are a domain where, in the coming decade, large quantitative and qualitative changes can be expected in services and applications, that ultimately will benefit from wireless multigigabit/s communication. Therefore, the need for such high data rates arises both in short-range scenarios and in medium-long range scenarios. Where a very huge bandwidth for multigigabit wireless communications can be made available as free spectrum without interference issues? The unique possibility is to look at EHF. Recently, there has been a lot of interest in the development of 60 GHz systems for the indoor and outdoor applications, because this bandwidth has been allocated in many countries as free spectrum. However, because of higher propagation loss due to oxygen absorption at this band, it is not suitable for very long links. Further, the FCC has made available 13 GHz of spectrum in the 70-95 GHz (away from the oxygen absorption band, in order to facilitate longer range communication) for semi-unlicensed use for directional point-to-point “last mile” links. However, above 60 GHz, both for long and short range, there is a lack of discussion on modulation, equalization, and algorithm design at physical layer. This work mainly aims at investigating the possibility to use innovative and advanced radio interfaces, as one based on IR UWB transmission technique, to realise multigigabit/s communications beyond 60 GHz. In particular, this work shows how an IR UWB communication system is sensitive to typical H/W not idealities beyond 60 GHz (Phase Noise, Timing Jitter, LNA and HPA distortions) and compares its performance with the ones of a more classical continuous wave communications system based on FSK modulation. The exploitation of such higher frequencies represents the most suitable solution to develop a cooperative global information infrastructure in order to guarantee the so-called “Gigabit Connectivity” through aerospace links making such a radio segment a potential “backbone on the air” for global wireless connectivity. Therefore, the use of “beyond Q/V bands” will be the necessary condition to develop a multipurpose network, as integration of terrestrial and space systems, in order to support forthcoming high-data-rate services demands. W band (75-110 GHz, respectively 4 -2.7 mm) could represent the answer to these needs due to the high bandwidth availability, short wavelength, reduced interference, small antenna size, allowing to propose many innovative services that need high-volume transfers. Currently, however, the performance behaviour of any solution for data transportation over W band frequencies across the Troposphere is still unknown, since no scientific and/or telecommunication mission has been realised, either on an experimental basis or in an operating mode. Therefore, missions in W band have to be studied in order to perform a first empirical evaluation of the Troposphere effects on the radio channel. Consequently, the last part of this work has been focused on the analysis and performance evaluation of future missions for the exploitation of W band too for satellite communications aiming at designing a full line of P/Ls operating in such a frequency range. The design and performance analysis of missions to perform a first empirical evaluation of the Troposphere effects on the W band radio channel represent the preliminary useful step for realising a “System of Systems” which is able to meet the high-quality data transmission requirements for a large number of end-users and data-oriented services.
42
Dalla, Pozza Nicola. "Receiver Design for Quantum Communication." Doctoral thesis, Università degli studi di Padova, 2013. http://hdl.handle.net/11577/3423448.
Full textAbstract:
Born about a century ago, Quantum Mechanics has revolutionized the description and the interpretation of Physics at sub-microscopic level.
In the last decades, due to the influence of mathematical and engineering research fields, Quantum Mechanics has given birth to related research areas like Quantum Computation, Quantum Information and Quantum Communication.
With the discovery of the laser, and later the development of fiber optics and satellite networks, Quantum Communication and Quantum Optics seems to have a natural field of application in Communication Systems.
Despite this, the interest in this technology and studies for communication purpose has been overshadowed by the great results in communication networks achieved in the last decades with classical paradigms. However, due to the increasing demand of communication data rate, system designers are now looking at Quantum Mechanics for new and more performanting solutions in communication purposes.
Early theoretical studies on Quantum Discrimination Theory and Quantum Information predict better performance for Communication Systems that take advantage of the quantum laws.
In addition, Quantum Mechanics provides the deepest description of the physical phenomena, and there are scenarios where a quantum model fits best, as in in deep space communications, where the received signal is really weak, or in a satellite networks, where we are interested in strongly reducing the power of transmitted signals, possibly without sacrificing performance significantly.
However, if on one side Quantum Communication Theory promises great gains in the performance of communication systems, on the other hand it fails to describe how to implement physical devices that reach these ultimate limits. So far, only a few architectures achieving these performances are known, and only for simple modulation formats.
We are interested in the scenario of optical communications, where the message transmitted is encoded in a sequence of coherent states.
Transmitter devices for coherent modulation are well known and consist in laser pulse generators. Instead, receiver implementations working at the quantum limit performance limit are yet to be found.
In this Thesis I deal with different topics in the quantum transmission scenario.
First, I review existing classical (suboptimal) and quantum (suboptimal and optimal) receiver schemes for the binary coherent modulation. I present a new formulation of the optimal scheme known as Dolinar Receiver with the multiple copies problem, focusing on the information gained during the measurement.
Second, I analyze the binary communication in a noisy environment, studying the error probability and the capacity of the binary channel induced. Given the description of the quantum channel, I optimize both the transmitted quantum states and the measurement operators employed in the communication.
Third, I consider the Pulse Position Modulation, that is particularly suitable for space and satellite communication due to its simplicity of implementation and high capacity. I review some known suboptimal receivers, and I propose a receiver scheme which approaches the limit performance predicted with quantum theory outperforming the existing schemes.
To sum up the results of this Thesis, in order to approach the limit performance predicted by Quantum Mechanics, an optimization is always necessary to exceed the classical effects and trigger the quantum phenomena. In particular, the information gained during the measurement plays an important role, for example in the definition of adaptive receivers. In this Thesis both these aspects have been deeply investigated.Formalizzata più di un secolo fa, la Meccanica Quantistica ha rivoluzionato la descrizione e l'interpretazione della Fisica a livello microscopico. Negli ultimi decenni, grazie all'influenza di studi affini nei campi della matematica e dell'ingegneria, la Meccanica Quantistica ha portato allo sviluppo di aree di ricerca quali la Computazione Quantistica, la teoria dell'Informazione Quantistica e le Comunicazioni Quantistiche. Con l'invenzione del laser, e i successivi sviluppi delle fibre ottiche e delle reti satellitari, la comunicazione quantistica e l'ottica quantistica hanno un naturale campo di applicazione nello studo nei sistemi di comunicazione. Nonostante ciò, l'interesse in questa tecnologia e gli studi quantistici sulle telecomunicazioni sono stati messi in ombra dai risultati nelle reti di comunicazione ottenuti negli ultimi decenni con paradigmi classici. Solo recentemente, a causa dell'aumento della richiesta di rate trasmissivo, i progettisti di sistemi di comunicazione guardano alla meccanica quantistica in cerca di soluzioni nuove e più efficienti. I primi studi teorici nella teoria quantistica della discriminazione e dell'informazione prevedono un notevole vantaggio nelle prestazioni se i sistemi di comunicazione sono progettati secondo le leggi della meccanica quantistica. Inoltre, la meccanica quantistica fornisce la più profonda descrizione dei fenomeni quantistici, e in alcuni scenario tale descrizione è più appropriata, come nel caso di comunicazioni dallo spazio profondo, dove il segnale ricevuto è estremamente debole, o nelle reti satellitari, dove siamo interessati a ridurre la potenza trasmessa con il segnale, senza sacrificare significativamente le prestazioni. Se da un lato le comunicazioni quantistiche promettono grandi guadagni in termini di performance, dall'altro lato non spiegano esplicitamente come costruire dispositivi che raggiungono questi limiti. Finora, solo pochi schemi di comunicazione che raggiungono questo limite sono conosciuti, e solo per formati di modulazione semplici. Lo scenario di nostro interesse è quello delle trasmissioni ottiche, dove un messaggio trasmesso viene codificato in una sequenza di stati coerenti. Dispositivi di trasmissione per la modulazione coerente sono noti (generatori laser), mentre ricevitori che lavorano nel regime quantistico sono ancora da sviluppare. In questo lavoro di Tesi sviluppo diversi temi nello scenario delle comunicazioni quantistiche. Inizialmente, riassumo gli schemi di ricezione classici (subottimi) e quantistici (ottimi e subottimi) per la modulazione binaria coerente. Successivamente presento una riformulazione dello schema ottimo noto come il ricevitore di Dolinar come un problema di copie multiple, focalizzandomi sull'informazione guadagnata durante l'operazione di misura. Successivamente, analizzo la comunicazione binaria in un ambiente rumoroso, studiando la probabilità di errore e la capacità del canale binario che si possono ottenere. Data una descrizione quantistica del canale, ottimizzo rispetto sia gli stati trasmessi che gli operatori di misura impiegati nella comunicazione. In seguito considero una modulazione più complessa, la Pulse Position Modulation, particolarmente adatta per le comunicazioni dallo spazio e satellitari, grazie alla semplicità di implementazione e all'alta capacità. In primo luogo rivedo alcuni ricevitori subottimi, e successivamente propongo uno schema di ricezione che approccia le prestazioni limite predette con la teoria quantistica, superando gli schemi esistenti in letteratura. Riassumendo i risultati della Tesi, per approcciare le prestazioni ottime predette dalla meccanica quantistica un procedimento di ottimizzazione è sempre necessario per superare gli effetti classici e innescare i fenomeni quantistici. In particolare, l'informazione guadagnata durante il procedimento di misura gioca un ruolo fondamentale, ad esempio nella definizione di ricevitori adattativi. In questo lavoro di Tesi entrambi questi aspetti sono stati investigati a fondo.
43
Naab-Levy, Adam O. "Enhanced Distance Measuring Equipment Data Broadcast Design, Analysis, Implementation, and Flight-Test Validation." Ohio University / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1449158180.
Full text
44
Wetzel, Benjamin. "Etudes expérimentales et numériques des instabilités non-linéaires et des vagues scélérates optiques." Phd thesis, Université de Franche-Comté, 2012. http://tel.archives-ouvertes.fr/tel-01002680.
Full textAbstract:
Ces travaux de thèse rapportent l'étude des instabilités non-linéaires et des évènements extrêmesse développant lors de la propagation guidée d'un champ électromagnétique au sein de fibresoptiques. Après un succinct rappel des divers processus linéaires et non-linéaires menant à lagénération de super continuum optique, nous montrons que le spectre de celui-ci peut présenterde larges fluctuations, incluant la formation d'événements extrêmes, dont les propriétés statistiqueset l'analogie avec les vagues scélérates hydrodynamiques sont abordées en détail. Nous présentonsune preuve de principe de l'application de ces fluctuations spectrales à la génération de nombres etde marches aléatoires et identifions le phénomène d'instabilité de modulation, ayant lieu lors de laphase initiale d'expansion spectrale du super continuum, comme principale contribution à la formationd'événements extrêmes. Ce mécanisme est étudié numériquement et analytiquement, en considérantune catégorie de solutions exactes de l'équation de Schrödinger non-linéaire présentant descaractéristiques de localisations singulières. Les résultats obtenus sont vérifiés expérimentalement,notamment grâce à un système de caractérisation spectrale en temps réel et à l'utilisation conjointede métriques statistiques innovantes (ex : cartographie de corrélations spectrales). L'excellent accordentre simulations et expériences a permis de valider les prédictions théoriques et d'accéder àune meilleure compréhension des dynamiques complexes inhérentes à la propagation non-linéaired'impulsions optiques.
45
Alsolami, Ibrahim. "Visible light communications with single-photon avalanche diodes." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:744eeb47-8bb6-4776-8b8f-f7b6374d89bd.
Full textAbstract:
This thesis explores the use of single-photon avalanche diodes (SPADs) for visible light communications (VLC). The high sensitivity of SPADs can potentially enhance the performance of VLC receivers. However, a SPAD-based system has challenges that need to be addressed before it can be considered as a viable option for VLC. The first challenge is the susceptibility of SPAD-based receivers to variations in ambient light. The high sensitivity of SPADs is advantageous for signal detection, but also makes SPADs vulnerable to variations in ambient light. In this thesis, the performance of a SPAD-based receiver is investigated under changing lighting conditions. Analytical expressions to quantify performance are derived, and an experiment is conducted to gain further understanding of system performance. It is shown that a SPAD-based receiver is highly sensitive to illumination changes when on-off keying (OOK) is employed, and that pulse-position modulation (PPM) is a preferred modulation scheme as it is more robust. The second challenge is broadcasting to SPAD-based receivers with different capabilities. A traditional broadcasting scheme is time-sharing, whereby a transmitter sends data to receivers in an alternating manner. Broadcasting to SPAD-based receivers is challenging as receivers may have diverse capabilities. In this thesis, a new multiresolution modulation scheme is proposed, which can potentially improve system performance over the traditional timesharing approach. The performance of the proposed scheme is analyzed, and a proof-of-concept experiment is performed to demonstrate its viability.
46
Rios, Clauson Sales do Nascimento. "ImplementaÃÃo de portas lÃgicas atravÃs da modulaÃÃo de pulsos por posiÃÃo (PPM) em filtros acÃstico-Ãpticos sintonizÃveis." Universidade Federal do CearÃ, 2006. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=2097.
Full textAbstract:
FundaÃÃo de Amparo à Pesquisa do Estado do CearÃNesta dissertaÃÃo foi estudada a aplicaÃÃo do filtro AcÃstico-Ãptico SintonizÃvel (AOTF), com a ModulaÃÃo de Pulsos por PosiÃÃo (PPM), objetivando implementar, utilizando o mÃtodo de Runge-Kutta de 4a ordem, portas lÃgicas (OR-OU e AND-E) Ãpticas operando com pulsos de luz ultracurtos (2ps). Neste trabalho à investigado o desempenho das portas considerando vÃrios comprimentos do filtro ( L) que integra a sua estrutura interna, com o intuito de obter o comprimento de filtro mais adequado para uma operaÃÃo satisfatÃria, em regime dispersivo, nÃo linear, sem perdas e com modulaÃÃo de fase cruzada (XPM). Esta investigaÃÃo à realizada em duas situaÃÃes: primeiramente, sÃo considerados filtros com automodulaÃÃo de fase (SPM) e GVD (dispersÃo da velocidade de grupo). Em um segundo momento, as mesmas portas sÃo obtidas com efeitos SPM, XPM e GVD agindo juntos no AOTF. Foi observado que para pulsos do tipo sÃliton, os efeitos da dispersÃo, da nÃo linearidade e da modulaÃÃo de fase cruzada exercem juntos uma forte influÃncia na propagaÃÃo do mesmo, provocando a quebra do pulso na saÃda do dispositivo quando utilizamos um comprimento maior para os filtros. Para dispositivos mais curtos, o pulso chaveado apresentou compressÃes e alargamentos temporais e espectrais, bem comodeslocamentos temporais nos dois modo de propagaÃÃo (TE e TM). ApÃs a escolha de um comprimento de filtro adequado, foi selecionado um deslocamento temporal Ãtimo a ser aplicado nos pulsos de entrada para conseguirmos, na saÃda da porta lÃgica, deslocamentos temporais satisfatÃrios (acertos) na aplicaÃÃo da modulaÃÃo PPM. Em seguida, introduzimos fases em um dos pulsos de entrada (TM), provocando um defasamento entre os pulsos TE e TM, reduzindo ainda mais a margem de erro PPM de operaÃÃo das portas. Finalmente, ao analisarmos as fases aplicadas no pulso TM (0 a 2), definirmos o melhor Ãngulo de fase para que as portas operem na regiÃo de acerto da modulaÃÃo PPM.
In this dissertation it was studied the application of the Acoustic Optical Tunable Filter (AOTF), with Pulse Position Modulation (PPM), aiming at to implement, using the method of Runge-Kutta of 4a order, logical gates (OR and AND) optical operating with pulses of light ultra shorts (2ps). In this work the acting of the gates is investigated, considering several lengths of the filter ( L) that integrates your internal structure, with the intention of obtaining the length of more appropriate filter for a satisfactory operation, in dispersion regime, nonlinear, without losses and with Cross Phase Modulation (XPM). This investigation is accomplished in two situations: firstly, filters are considered with Self Phase Modulation (SPM) and GVD (group-velocity dispersion). In a second moment, the same gates are obtained with effects SPM, XPM and GVD, acting together in AOTF. It was observed that for pulses of the type soliton, the effects of the dispersion, of the nonlinearity and of the cross phase modulation exercise together a strong influences in the propagation of the same, provoking the break of the pulse in the exit of the device when we used a larger length for the filters. For shorter devices, the switched pulse presented temporary and spectral compression and spread, as well as, displacement in the time in the two propagation modes (TE and TM). After the choice of a length of appropriate filter, a great temporary displacement was selected to be applied in the input pulses for us to get, in the exit of the logical gate, satisfactory temporary displacements (successes) in the application of the PPM modulation. Soon after, we introduced phases in one of the entrance pulses (TM), provoking a phase displacement among TE and TM pulses, still reducing more the margin of error PPM of operation of the gates. Finally, to the we analyze the applied phases in the pulse TM (0 to 2), we defined the best phase angle for the gates to operate in the success area of the PPM modulation.
47
Dušek, Jiří. "Elektronická škrticí klapka." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2011. http://www.nusl.cz/ntk/nusl-219313.
Full textAbstract:
The aim of this master’s thesis was to analyze the contemporary electronic throttles and the requirements imposed on them. Then to build the mathematical model, identify parameters of the given electronic throttle, proceed the verification and on its basis to build the simulation model. There were selected suitable control and high power components to control the electronic throttle. Due to the knowledge of these parameters the simulation model was extended. For this extended simulation model was designed the position cascade controller with speed and current control loop. Using the designed controller the implementation of the electronic throttle control and the available high power and control module was realized.
48
Khlaief, Amor. "Contribution à la commande vectorielle sans capteur mécanique des machines synchrones à aimants permanents (MSAP)." Phd thesis, Aix-Marseille Université, 2012. http://tel.archives-ouvertes.fr/tel-00814276.
Full textAbstract:
Ce travail de recherche s'intéresse à la commande sans capteur mécanique du moteur synchrone à aimants permanents (MSAP) à pôles saillants, particulièrement en basse vitesse, avec détection de la position initiale du rotor. Après une présentation des techniques et approches qui ont initié nos travaux, en terme d'estimation de la vitesse et/ou de la position, nous avons choisi celles qui présentent plus d'intérêt de point de vue stabilité, robustesse, précision et simplicité d'implémentation. La première approche est basée sur le Système Adaptatif avec Modèle de Référence (MRAS). Quant à la deuxième, elle est réalisée autour d'un observateur non-linéaire pour l'estimation de la position et de la vitesse du MSAP à pôles saillants. Les deux techniques d'observation de la vitesse sont associées à une commande par orientation du flux rotorique avec la technique MLI vectorielle. Pour détecter la position initiale du rotor, nous avons utilisé une nouvelle approche qui permet d'estimer cette position avec une incertitude de 5° mécanique. Cette nouvelle approche est basée sur l'application de signaux tests aux bornes des phases statoriques du MSAP. Des résultats de simulation et expérimentaux sont présentés tout au long de ces travaux pour valider les études théoriques de la commande vectorielle sans capteur mécanique du MSAP. Enfin, nous avons étudié et analysé les performances de la commande tolérante aux défauts sans capteur mécanique du MSAP en présence de défaillances de types transistors à l'état-off. Les résultats expérimentaux obtenus avec les deux approches d'estimation de la vitesse en utilisant l'observateur MRAS et un observateur non linéaire ont permis d'améliorer la fiabilité du système de manière à rendre possible la commande vectorielle sans capteur mécanique en mode dégradé (alimentation avec deux bras de l'onduleur). En effet, les résultats de la commande sans capteur mécanique de la MSAP en mode dégradé montrent que l'observateur non linéaire est le mieux adapté pour ce type de fonctionnement car il présente de faible ondulation du couple et de vitesse. A l'aide d'un banc d'essais que nous avons développé au laboratoire LSIS-pôle Ecole Centrale de Marseille (ECM), nous avons pu valider expérimentalement les différentes approches proposées dans ce travail de recherche. Les résultats obtenus montrent l'efficacité des techniques mises en œuvre pour la commande vectorielle sans capteur mécanique du MSAP à pôle saillant en termes de robustesse, stabilité, précision et rapidité.
49
Aboelhassan, Mustafa Osman Elrayah. "Robustní řízení synchronního stroje s permanentními magnety a spínaným tokem." Doctoral thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2013. http://www.nusl.cz/ntk/nusl-233605.
Full textAbstract:
Je jasné, že nejúspěšnější konstrukce zahrnuje postup vícefázového řízení, ve kterém každá fáze může být považována za samostatný modul. Provoz kterékoliv z jednotek musí mít minimální vliv na ostatní, a to tak, že v případě selhání jedné jednotky ostatní mohou být v provozu neovlivněny. Modulární řešení vyžaduje minimální elektrické, magnetické a tepelné ovlivnění mezi fázemi řízení (měniče). Synchronní stroje s pulzním tokem a permanentními magnety se jeví jako atraktivní typ stroje, jejíž přednostmi jsou vysoký kroutící moment, jednoduchá a robustní konstrukce rotoru a skutečnost, že permanentní magnety i cívky jsou umístěny společně na statoru. FS-PMSM jsou poměrně nové typy střídavého stroje stator-permanentní magnet, které představují významné přednosti na rozdíl od konvenčních rotorů - velký kroutící moment, vysoký točivý moment, v podstatě sinusové zpětné EMF křivky, zároveň kompaktní a robustní konstrukce díky umístění magnetů a vinutí kotvy na statoru. Srovnání výsledků mezi FS-PMSM a klasickými motory na povrchu upevněnými PM (SPM) se stejnými parametry ukazuje, že FS-PMSM vykazuje větší vzduchové mezery hustoty toku, vyšší točivý moment na ztráty v mědi, ale také vyšší pulzaci díky reluktančnímu momentu. Pro stroje buzené permanentními magnety se jedná o tradiční rozpor mezi požadavkem na vysoký kroutící moment pod základní rychlostí (oblast konstantního momentu) a provozem nad základní rychlostí (oblast konstantního výkonu), zejména pro aplikace v hybridních vozidlech. Je předložena nová topologie synchronního stroje s permanentními magnety a spínaným tokem odolného proti poruchám, která je schopná provozu během vinutí naprázdno a zkratovaného vinutí i poruchách měniče. Schéma je založeno na dvojitě vinutém motoru napájeném ze dvou oddělených vektorově řízených napěťových zdrojů. Vinutí jsou uspořádána takovým způsobem, aby tvořila dvě nezávislé a oddělené sady. Simulace a experimentální výzkum zpřesní výkon během obou scénářů jak za normálního provozu, tak za poruch včetně zkratových závad a ukáží robustnost pohonu za těchto podmínek. Tato práce byla publikována v deseti konferenčních příspěvcích, dvou časopisech a knižní kapitole, kde byly představeny jak topologie pohonu a aplikovaná řídící schémata, tak analýzy jeho schopnosti odolávat poruchám.
50
WU, YU-HUNG, and 吳宇弘. "Performance Evaluation of Joint Pulse Width Modulation and Pulse Position Modulation Visible Light Communications." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/586pts.
Full textAbstract:
碩士國立雲林科技大學
電子工程系
105
This research presents the simulation results of pulse width modulation and pulse position modulation (Joint PWM/PPM). During the PPM data transmissions, the PWM duty cycle changed from 40% to 80%, in the process of data transmission simultaneously to achieve dimming control of visible light communication (VLC). LED channel effect of VLC, resulting in the phenomenon of inter-symbol interference (ISI), so this thesis uses the post-equalization circuit to improve the LED bandwidth limit, and display PPM signal in different guard time (slot) bit error rate results. In the 5×5×3m indoor environment system, we get the signal-to-noise ratio (SNR) into the Joint PWM/PPM simulation to obtain the bit error rate distributions. It is known from the simulation results, that the system is added to the guard time of PPM signal, and the result of the bit error rate after the equalization is the best and the distribution is the most uniform.