Dissertations / Theses on the topic '100501 Antennas and Propagation'
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1
Vural, Serdar. "Information propagation in wireless sensor networks using directional antennas." Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1188006033.
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Hope, David C. "Towards a wireless aircraft : propagation, antennas and radio standards." Thesis, University of York, 2011. http://etheses.whiterose.ac.uk/1900/.
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The replacement of many of of an aircraft’s wired interconnects with wireless data connections would offer a number of benefits. These include: weight reduction, easier maintenance, faster aircraft design, simpler retrofitting and greater redundancy. However, attempting to do this produces a lot of challenges and risks because data connections on an aircraft must meet very high standards for reliability. This PhD Thesis lays out the main challenges of the propagation environment explaining that large sections of an aircraft may be highly resonant and explain- ing the difficulties this presents for wireless receivers. Modern wireless standards are explored and the question of how suitable they would be for this application is addressed. Two standards are recommended: 802.11n and ZigBee and these are tested in a variety of environments such as a reverberation chamber and avionics bays in a Tornado, to demonstrate the levels of time delay spread needed to prevent a wireless system from working. In particular, the sta- tistical distribution of the channel is emphasised and we show how one must expect Rayleigh fading of the signal even over short distances which has implications when the channel is time varying, such as in an aircraft wing. A variety of approaches are suggested for reducing the probability of system failure by adding redundancy in various forms to boost link availability. As well as the detailed study of propagation in an airframe some of the general issues of a wireless aircraft are addressed such as data rates, what types of system could be made wireless and what types of data bus would wireless be replacing. As this work was done under the Flaviir UAV program, some of the collaborative work is presented showing the design of a novel patch antenna written onto the aircraft skin by a genetic algorithm.
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Wu, Xianyue. "Antennas and propagation for body area networks at 60 GHZ." Thesis, University of Birmingham, 2014. http://etheses.bham.ac.uk//id/eprint/4786/.
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The advent of wireless body area networks (WBANs) and their use in a wide range of applications from consumer electronics to military purposes, dictates the need to investigate to the behaviour of antennas and wave propagation on the body in depth. Although this area has been extensively studied in the past decade, some issues are still not satisfactorily solved for communication systems for WBANs at ISM bands and UWB such as compact and high efficiency antenna design, privacy and security, interference mitigation and achieving high data rates. This thesis proposed an alternative wireless solution for body area networks by adopting 60 GHz radio. On-body channels at 60 GHz have been characterised using monopole and horn antennas. Horn antennas achieve significantly improved path gain in the stable channels but are susceptible to shadowing in the mobile channels due to body movements. However, interference mitigation and covertness for 60 GHz WBANs at the physical layer are improved due to high attenuation of 60 GHz signals. Significant increase of carrier-to-interference ratio is observed for 60 GHz WBANs compared to 2.45 GHz. A model of estimating the maximum detection distance at a threshold probability for detecting a WBAN wearing soldier in a battlefield is proposed. Fixed-beam directional antennas and reconfigurable antennas are designed for 60 GHz WBANs and channel measurements using these antennas are conducted. Results show beam-reconfigurability of the antenna improves the link performance compared to fixed-beam antennas at 60 GHz.
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Allen, Ben. "Smart antennas for high data rate FDD wireless links." Thesis, University of Bristol, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.364956.
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Tsivgoulis, Georgios. "Source localization in wireless sensor networks with randomly distributed elements under multipath propagation conditions." Thesis, Monterey, Calif. : Naval Postgraduate School, 2009. http://edocs.nps.edu/npspubs/scholarly/theses/2009/March/09Mar%5FTsivgoulis.pdf.
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Thesis (Electrical Engineer and M.S. in Electrical Engineering)--Naval Postgraduate School, March 2009.Thesis Advisor(s): Tummala, Murali ; McEachen, John C. "March 2009." Description based on title screen as viewed on April 23, 2009. Author(s) subject terms: Wireless Sensor Network, Direction of Arrival, DOA, Random Arrays, Smart Antennas, Time Difference of Arrival, TDOA, Multipath Propagation, Source Localization. Includes bibliographical references (p. 89-92). Also available in print.
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Kavak, Adnan. "Vector propagation channel studies for smart antenna wireless communication systems /." Full text (PDF) from UMI/Dissertation Abstracts International, 2000. http://wwwlib.umi.com/cr/utexas/fullcit?p3004302.
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Chang, Teck Keng. "Active frequency selective surfaces." Thesis, University of Kent, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.281659.
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Sani, Andrea. "Modelling and characterisation of antennas and propagation for body-centric wireless communication." Thesis, Queen Mary, University of London, 2010. http://qmro.qmul.ac.uk/xmlui/handle/123456789/596.
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Body-Centric Wireless Communication (BCWC) is a central point in the development of fourth generation mobile communications. The continuous miniaturisation of sensors, in addition to the advancement in wearable electronics, embedded software, digital signal processing and biomedical technologies, have led to a new concept of usercentric networks, where devices can be carried in the user’s pockets, attached to the user’s body or even implanted. Body-centric wireless networks take their place within the personal area networks, body area networks and body sensor networks which are all emerging technologies that have a broad range of applications such as healthcare and personal entertainment. The major difference between BCWC and conventional wireless systems is the radio channel over which the communication takes place. The human body is a hostile environment from radio propagation perspective and it is therefore important to understand and characterise the effect of the human body on the antenna elements, the radio channel parameters and hence the system performance. This is presented and highlighted in the thesis through a combination of experimental and electromagnetic numerical investigations, with a particular emphasis to the numerical analysis based on the finite-difference time-domain technique. The presented research work encapsulates the characteristics of the narrowband (2.4 GHz) and ultra wide-band (3-10 GHz) on-body radio channels with respect to different digital phantoms, body postures, and antenna types hence highlighting the effect of subject-specific modelling, static and dynamic environments and antenna performance on the overall body-centric network. The investigations covered extend further to include in-body communications where the radio channel for telemetry with medical implants is also analysed by considering the effect of different digital phantoms on the radio channel characteristics. The study supports the significance of developing powerful and reliable numerical modelling to be used in conjunction with measurement campaigns for a comprehensive understanding of the radio channel in body-centric wireless communication. It also emphasises the importance of considering subject-specific electromagnetic modelling to provide a reliable prediction of the network performance.
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Ibraheem, Ali Ahmed Younis. "Implanted Antennas and Intra-Body Propagation Channel for Wireless Body Area Network." Diss., Virginia Tech, 2014. http://hdl.handle.net/10919/50936.
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Implanted Devices are important components of the Wireless Body Area Network (WBAN) as a promising technology in biotelemetry, e-health care and hyperthermia applications. The design of WBAN faces many challenges, such as frequency band selection, channel modeling, antenna design, physical layer (PHY) protocol design, medium access control (MAC) protocol design and power source. This research focuses on the design of implanted antennas, channel modeling between implanted devices and Wireless Power Transfer (WPT) for implanted devices. An implanted antenna needs to be small while it maintains Specific Absorption Rate (SAR) and is able to cope with the detuning effect due to the electrical properties of human body tissues. Most of the proposed antennas for implanted applications are electric field antennas, which have a high near-zone electric field and, therefore, a high SAR and are sensitive to the detuning effect. This work is devoted to designing a miniaturized magnetic field antenna to overcome the above limitations. The proposed Electrically Coupled Loop Antenna (ECLA) has a low electric field in the near-zone and, therefore, has a small SAR and is less sensitive to the detuning effect. The performance of ECLA, channel model between implanted devices using Path Loss (PL) and WPT for implanted devices are studied inside different human body models using simulation software and validated using experimental work. The study is done at different frequency bands: Medical Implanted Communication Services (MICS) band, Industrial Scientific and Medical (ISM) band and 3.5 GHz band using ECLA. It was found that the proposed ECLA has a better performance compared to the previous designs of implanted antennas. Based on our study, the MICS band has the best propagation channel inside the human body model among the allowed frequency bands. The maximum PL inside the human body between an implanted antenna and a base station on the surface is about 90 dB. WPT for implanted devices has been investigated as well, and it has been shown that for a device located at 2 cm inside the human body with an antenna radius of 1 cm an efficiency of 63% can be achieved using the proposed ECLA.Ph. D.
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Fragoulis, Ioannis. "An investigation of two broadband HF shipboard communication antennas." Thesis, Monterey, California : Naval Postgraduate School, 1990. http://handle.dtic.mil/100.2/ADA245608.
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Thesis (M.S. in Electrical Engineering)--Naval Postgraduate School, December 1990.Thesis Advisor(s): Adler, Richard W. Second Reader: Vincent, Wilbur R. "December 1990." Description based on title screen as viewed on March 30, 2010. DTIC Identifier(s): Ship Antennas, Communication Antennas, Antenna Radiation Patterns, High Frequency, Multiwire Antennas, Theses. Author(s) subject terms: Inverted Cone Antenna, Computer Antenna Modeling, NEC, HF Antennas, Shipboard Antenna. Includes bibliographical references (p. 95). Also available in print.
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Schulte, Joseph Thomas 1957. "A system to measure the phase shift and attenuation of underground HF electromagnetic propagation." Thesis, The University of Arizona, 1989. http://hdl.handle.net/10150/277177.
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This thesis discusses the theory and limitations of a system that has been designed and constructed for the purpose of measuring the phase shift and attenuation of high-frequency (15 MHZ) electromagnetic waves propagating between two insulated antennas that have been lowered down air-filled boreholes (cased with PVC pipe) at San Xavier Mine, Pima County, Arizona. Both the transmitting and receiving antennas are center-fed, sleeve dipoles that have been tuned to approximately their resonant lengths. The insulated-sleeve dipole antenna is modelled as the inner conductor of a radiating, coaxial transmission-line, which allows simple transmission-line formulas to be used in approximating the antenna impedance and current distribution along the antenna. Experimental results at the San Xavier Mine indicate the analogy is valid. Consequently, the most easily interpreted and repeatable measurements have been made with the antennas centered in the borehole.
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Cooper, James Roger. "Novel wireless sensor configurations incorporating isotropic radiators on conformal artificial magnetic conductors." Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/52246.
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The objective of the presented research is to develop a novel, ink-jet printed, chipless, passive, wireless sensor topology, which can radiate in a near isotropic pattern without interference from embedded devices, for use in dispersed sensor networks. This objective includes the development of a hardware based, uniquely identifiable, collision avoidance communication method, and an integrated sensor system that is easily integrated into the topology.
Wireless sensor networks can be and are used in military, medical and industrial applications; and the demand for them is ever growing. However, current sensor networks have various trade-offs and limitations, including cost, number of distinguishable nodes, and ease of manufacturing. These trade-offs lead to unique sensors needing to be designed for each situation. To develop a widely used module, a topology must be developed that can meet as many demands as possible with fair tradeoffs.
Many of the above proposed criteria for the topology are already integrated into RFID technology. Therefore, much of the research is the application and advancement of current RFID technology for the purpose of designing the topology. The research begins with the theory and design of conformal artificial magnetic conductors, which is used in the design of a near isotropic radiator and isolated core for device embedding. Then, novel fabrication techniques will be investigated and deployed in the fabrication of the topology. Next, a novel "smart skin" sensor is developed which is easily integrated into the desired fabrication technique. Finally, an anti-collision RFID circuit for on-tag placement, which is based on frequency-doubling transceivers, is designed, which can also be easily integrated into the final topology.
This module is designed for use with a variety of different sensors. This versatility gives it ruggedness for use in many different environments. For proof of concept, this topology is fabricated and tested against current commercially sold tags.
Through the design and testing of the radiator, circuitry, and embedded sensors, it is shown that this design is a suitable topology for use in many different environments and applications.
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Burge, Joseph. "Polarisation MIMO indoor wireless communications using highly compact antennas and platforms." Thesis, University of Manchester, 2017. https://www.research.manchester.ac.uk/portal/en/theses/polarisation-mimo-indoor-wireless-communications-using-highly-compact-antennas-and-platforms(e23fb834-e17e-4434-88c9-90c57d99e055).html.
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In the indoor environment, multipath fading causes the received signal amplitude to fluctuate rapidly over space and frequency. Multiple-in multiple-out (MIMO) systems overcome this phenomenon through the use of multiple antennas on transmitters and receivers. This establishes multiple independent MIMO sub-channels between antenna pairs, which allows a theoretical increase in capacity which is linear with the number of antennas, while requiring no additional power or bandwidth expenditure. The capacity increase is reliant upon MIMO sub-channels being well decorrelated. Decorrelation may be achieved by separating antennas in space. On devices where space is limited, an alternative approach is to use antennas with orthogonal polarisations, which may be positioned closer together. Existing literature states that the performance of polarisation MIMO systems is typically inferior to that of spatial MIMO systems under diversity applications, but can be superior in multiplexing applications. These statements are based on the analysis of a statistical channel model, using channel conditions assumed to be typical of an ideal polarisation MIMO system. There is little existing literature which examines how close these assumptions are to a practical polarisation MIMO channel, or whether the above statements remain true of practical systems. This thesis presents a novel end-to-end, predominantly deterministic approach to the modelling of polarisation MIMO systems. A bespoke MIMO channel model is used to estimate capacity and error rate under diversity and spatial multiplexing applications in the indoor environment. The parameters of the channel model are obtained deterministically from a ray launching propagation model, using antenna patterns of orthogonally polarised small antenna systems positioned in the indoor environment. The individual differences in the channel gains and K-factors of each sub-channel are accounted for. Correlation is accounted for using a full correlation matrix, rather than the Kronecker model. Particular attention is paid to mutual coupling of closely spaced antennas. Using this analysis, it is shown that for practical antennas and systems conditions of the polarisation MIMO channel may differ from those assumed in literature. The effect of this in terms of channel capacity and system bit error rate is directly determined and presented. Performance of polarisation MIMO systems, using co-located and spatially separate orthogonally polarised antennas, is compared to that of spatial MIMO systems, which use co-polar antennas with limited spatial separation. Additionally, comparison is made between compact polarisation MIMO systems which use orthogonal linear polarised antennas and those using orthogonal circular polarised antennas. Further analysis examines the significant effect of objects in the antenna near-field regions. The effects of the presence of a metal case on antenna performance are presented, before its impact on the channel conditions and ultimately the resultant MIMO performance is shown.
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Griffin, Joshua David. "High-frequency modulated-backscatter communication using multiple antennas." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/28087.
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Thesis (M. S.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2009.Committee Chair: Durgin, Gregory; Committee Member: Ingram, Mary Ann; Committee Member: Nikitin, Pavel; Committee Member: Peterson, Andrew; Committee Member: Steffes, Paul.
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Wang-Hurst, Kathy Weiquan. "Analysis of Path Loss from a Transmitter in an Aircraft Cabin to an Exterior Fuselage-Mounted Antenna." Thesis, Virginia Tech, 2007. http://hdl.handle.net/10919/36237.
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It is important to investigate the threat posed to commercial aircraft by on board electronic
transmitters in the passenger cabin and the cargo holds of large transport aircraft. These
transmitters may be in the form of unintentional use of portable electronic devices or even
intentional radio frequency (RF) threat sources from terrorists. Thus, it is of interest to
determine the "interference path loss" (IPL) from a transmitting device inside the cabin
of such aircraft to the antenna terminals of a potential victim system of the aircraft. Past
studies have concentrated on measurements. These efforts to measure IPL directly have
demonstrated that accurate and repeatible measurements are difficult to obtain. Very little
modeling work has been done successfully to understand the IPL on aircraft. In this thesis,
we propose a 3-step methodology to quantify the interference path loss (IPL). We then apply
this methodology to a broad class of aircraft and show results. To validate our results, we
compare our findings to known measurements and discuss possible sources of errors. Finally
we suggest areas of improvement to our analysis and propose future work.Master of Science
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Aagaard, Fransson Erik Johannes, and Tobias Wall-Horgen. "Building and Evaluating a 3D Scanning System for Measurementsand Estimation of Antennas and Propagation Channels." Thesis, KTH, Elektroteknisk teori och konstruktion, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-104802.
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Wireless communications rely, among other things, on theunderstanding of the properties of the radio propagationchannel, the antennas and their interplay. Adequate measurementsare required to verify theoretical models and togain knowledge of the channel behavior and antenna performance.As a result of this master thesis we built a 3D fieldscanner measurement system to predict multipath propagationand to measure antenna characteristics. The 3Dscanner allows measuring a signal at the point of interestalong a line, on a surface or within a volume in space. In orderto evaluate the system, we have performed narrowbandchannel sounding measurements of the spatial distributionof waves impinging at an imaginary spherical sector. Datawas used to estimate the Angle-of-Arrivals (AoA) and amplitudeof the waves. An estimation method is presented tosolve the resulting inverse problem by means of regularizationwith truncated singular value decomposition. The regularizedsolution was then further improved with the helpof a successive interference cancellation algorithm. Beforeapplying the method to measurement data, it was testedon synthetic data to evaluate its performance as a functionof the noise level and the number of impinging waves. Inorder to minimize estimation errors it was also required tofind the phase center of the horn antenna used in the channelmeasurements. The task was accomplished by directmeasurements and by the regularization method, both resultsbeing in good agreement.
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Ranvier, Sylvain. "Radiowave propagation and antennas for high data rate mobile communications in the 60 GHz band." Nice, 2009. http://www.theses.fr/2009NICE4063.
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La bande de fréquence millimétrique autour de 60 GHz est considérée comme l’une des meilleures options pour l’implémentation des réseaux sans fils à très hauts débits de type WPAN (wireless personal area network). De plus, les systèmes multi-antennes de type MIMO (multiple-input multiple-output) sont très prometteurs. Ils peuvent augmenter de manière significative l’efficacité spectrale ou la fiabilité des communications sans fil. De ce fait, l’utilisation de systèmes multi-antennes à 60 GHz est, théoriquement, très prometteuse. Bien que les performances des systèmes MIMO aient été étudiées de manière approfondie à la fois théoriquement et expérimentalement à basses fréquences (2 et 5 GHz), il y a clairement un manque d’évaluation expérimentale de ces systèmes à 60 GHz. De plus, la conception et l’évaluation d’antennes millimétriques compactes à bas coûts pour des applications de type WPAN sont des sujets sur lesquels beaucoup de recherches doivent être encore faites. Dans la première partie de la thèse, le premier sondeur de canal MIMO à 60 GHz est présenté. Ce système, construit à partir d’un sondeur existant pour 2 et 5 GHz, utilise des réseaux d’antennes virtuelles. Afin d’améliorer la résolution temporelle, deux autres systèmes de mesure ont été développés. Le premier est construit à partir d’un sondeur ultra large bande et le second à partir d’un analyseur vectoriel de réseau. Ces systèmes permettent la caractérisation totale du canal MIMO dans les domaines temporel et angulaire. Dans la seconde partie, les performances de techniques pour systèmes multi-antennes sont analysées grâce aux mesures obtenues dans la première partie de la thèse. Les trois techniques étudiées sont: MIMO, MIMO avec sélection d’antennes et dépointage de faisceau. Les résultats indiquent que la capacité du canal MIMO mesuré est relativement proche de celle d’un canal idéal. Dans des conditions réalistes, la capacité obtenue grâce à la technique MIMO avec sélection d’antennes est souvent inférieure à celle obtenue avec la technique MIMO. Par ailleurs, lorsque l’on considère un réseau à déphasage avec des pertes réalistes, il apparait que la capacité obtenue avec la technique MIMO est presque toujours supérieure à celle obtenue avec la technique du dépointage du faisceau. Dans la dernière partie de la thèse, une antenne omnidirectionnelle est présentée. Cette antenne convient parfaitement aux applications de types WPAN car elle est plane et n’utilise qu’une seule couche de métallisation, ce qui la rend facile à réaliser et peut coûteuse. De plus, un banc de mesure quasi-3D de diagrammes de rayonnement d’antennes à 60 GHz à été développé. Ce système a une très bonne répétabilité. Le rayonnement de la pointe elle-même a été mesuré et les résultats indiquent que c’est la principale limitation de la dynamique d’amplitude de ce systèmeThe 60 GHz MIMO systems are seen as some of the best candidates for the implementation of future high data-rate short range communications systems such as wireless personal area networks (WPAN). Although the performance of MIMO systems has been studied thoroughly theoretically and experimentally at lower frequencies like at 2 and 5 GHz, there is a clear lack of measurement data and experimental performance evaluations of MIMO techniques at 60 GHz. Furthermore, more effort is still needed in the design and evaluation of compact low cost 60 GHz antennas for communication applications. In the first part of the thesis, the first 60 GHz MIMO channel measurement system is presented. It is based on a previously developed 2 and 5 GHz sounder and frequency converters. This system uses virtual antenna arrays to create the channel matrix. A measurement campaign is reported. In order to improve the delay resolution, two other MIMO measurement systems are presented, based on an ultra wide band (UWB) sounder and a vector network analyzer (VNA). Those systems allow full characterization of the MIMO channel in the delay and angular domains. In the second part of this work, the performance of multi-antenna techniques is evaluated based on the measurement data obtained in the first part of the thesis. Three of the most promising multi-antenna techniques, namely MIMO, antenna selection MIMO, and beam steering, are analyzed and compared. The presented results indicate that the mutual information of the measured MIMO channel is quite close to that of the independent and identically distributed (i. I. D. ) MIMO Rayleigh channel. Furthermore, in realistic conditions it is seen that MIMO-antenna selection often leads to lower mutual information than traditional MIMO with the same number of RF chains. Moreover, it is shown that when considering phase shifters with realistic losses, MIMO technique almost always outperforms beam steering technique. In the last part of the thesis a 60 GHz planar omnidirectional antenna is presented. This antenna is very suitable for communications applications since it has low profile and uses a metal layer only on one side of the substrate. Therefore, it can be manufactured easily and at very low cost. In addition, an advanced quasi full 3-D radiation pattern measurement system has been developed to evaluate probe-fed antennas. Very good measurement repeatability is reported. The radiation of the probe is analyzed and is seen to be the main limitation of the dynamic range of the measurement setup
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Srivastava, Vikash Umeshchandra. "Smart Antennas & Power Management in Wireless Networks." Thesis, Virginia Tech, 2003. http://hdl.handle.net/10919/31244.
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The proliferation of wireless ad-hoc networks especially wireless LAN (IEEE 802.11b Standard) in the commercial market in recent years has reached a critical mass. The adoption and strong support of wireless IEEE 802.11 standard, coupled with the consequent decline in costs, has made wireless LAN deployment as one of the fastest growth area in communication access technology. With the ever increasing use of wireless LAN technology the various networks are reaching their full capacity in terms of network throughput, number of users and interference level in the wireless channel.
In this thesis work I propose to the use smart antenna technology and a power management scheme in the wireless ad-hoc networks to increase the network capacity in terms of throughput, number of simultaneous communication and to lower the average transmit power and consequently co-channel interference. Power management scheme can be used to maximize the power efficiency of the transmitter by choosing an optimum transmit power level. Smart antenna or adaptive antenna array technology has reached a level of sophistication that it is feasible to use it on small mobile terminals like handheld PDA, LAPTOP and other mobile devices with limited battery power.
The simulation results of various ad â hoc network scenario shows that there are significant gains to be had if these technologies can be integrated in the existing wireless LAN physical layer and/or in the standard them self. Smart antennas along with slight modification in channel access scheme reduce co-channel interference dramatically and increases the number of simultaneous transmissions hence improves network throughput. Power management algorithm is shown to improve average transmission of a node.
We present a mathematical framework to characterize the outage probability of cellular mobile radio system with selective co-channel interference receiver in overloaded array environments. The mathematical framework outlines a general numerical procedure for computing the probability of outage of a cellular mobile radio system that is equipped with a smart antenna to suppress a few strongest co-channel interferers (CCI) out of a total of NI active interferers by null steering.Master of Science
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Bayram, Ahmet. "A Study of Indoor Ultra-wideband Propagation Measurement and Characterization." Thesis, Virginia Tech, 2004. http://hdl.handle.net/10919/32748.
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Ultra-wideband (UWB) communication is emerging as a new wireless technology, which promises high data rates with low interference and low power consumption. The development of such UWB systems requires a sufficiently large amount of data to characterize the propagation behavior of UWB signals in indoor environments and develop accurate channel models. This thesis focuses primarily on a frequency-domain approach for propagation measurements and characterization of indoor UWB channels. This approach is based on measurements of the amplitude using a scalar network analyzer and retrieval of the phase from the amplitude data using a Hilbert transform relationship.
Extensive propagation data are collected in a frequency range of 1 to 12 GHz in two buildings on Virginia Tech campus. Using the data, channel characterization results are obtained and compared to those based on time-domain measurements. Some statistical results for small-scale fading, path loss exponent, and signal quality are presented. This comparison validates the accuracy of measured results for the UWB measurement campaign. The measured data also reaffirms the immunity of UWB propagation to small-scale fading which is present in narrowband wireless communication systems.
In addition to channel propagation measurements, signal distortions in UWB links, due to bandwidth limitations of antenna characteristics as well as the dispersive behavior of building materials, are also examined. In particular, the distortion of radiated signals by TEM horn antennas along off-boresight directions are studied experimentally. Furthermore, pulse distortions resulting from propagation through dispersive walls are demonstrated by simulation. The roles of receive-transmit antennas in a UWB link are examined, and the requirements for gain, input impedance, polarization, and phase of the radiated signal necessary for minimization of signal distortions are pointed out.
Master of Science
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Bhat, Nitin. "An Antenna Specific Site Modeling Tool for Interactive Computation of Coverage Regions for Indoor Wireless Communication." Thesis, Virginia Tech, 1998. http://hdl.handle.net/10919/31317.
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A goal of indoor wireless communication is to strategically place RF base stations
to obtain optimum signal coverage at the lowest cost and power. Traditionally,
transceiver locations have been selected by human experts who rely on experience and
heuristics to obtain a near-optimum placement. Current methods depend on involved on-site
communication measurements and crude statistical modeling of the obtained data
which is time consuming and prohibitive in cost. Given the inherent variability of the
indoor environment, such a method often yields poor efficiency. As an example, it is
possible that more power than required or extra number of transceivers were used. This
thesis describes an interactive software system that can be used to aid transceiver
placement. The tool is easy to use and is targeted at users who are not experts in wireless
communication system design. Once the transceiver locations are selected by the user
within a graphical floor plan, the system uses simple path-loss models to predict coverage
regions for each transceiver. The coverage regions are highlighted to indicate expected
coverage. Earlier work assumed isotropic transceivers and had limited directional
transmitter support. This thesis describes how the tool has been enhanced to support a
wide range of 3D antenna patterns as encountered in practical situations. The tool has
also been expanded to accommodate more partition types and to report area of coverage.
The resulting system is expected to be very useful in the practical deployment of indoor
wireless systems.Master of Science
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Niang, Anna. "Antennes miniatures et structures électromagnétiques à circuits non-Foster." Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLS007/document.
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La recherche de nouveaux matériaux a permis de nouveaux développements au cours de ces dernières décennies. Ce sont entre autres les diélectriques artificiels ou encore les métamatériaux. Cependant, si ces matériaux restent passifs, malgré tous les développements possibles, les performances des antennes, ou autres structures électromagnétiques qui découlent d’eux seront toujours confrontés aux mêmes limitations fondamentales. En intégrant des circuits actifs dans ces matériaux, par exemple des résistances négatives, des capacités négatives et des inductances négatives, il est possible de dépasser ces limitations ainsi les propriétés synthétisables et les applications d’ingénierie pourront être significativement élargies. En effet, cela permettrait de créer des matériaux et des dispositifs dont les propriétés ne seront pas possibles autrement et surpasseraient celles des matériaux existant dans la nature. Cette thèse a été l’occasion dans un premier temps d’utiliser les circuits non-Foster qui sont des circuits à rétroaction actif, pour l’adaptation d’une antenne électriquement petite à basses fréquence. Ceci a permis de mettre en évidence ses avantages par rapport à une adaptation passive plus conventionnelle.Ensuite, des capacités négatives ainsi que des inductances négatives et positives ont été conçues. Leur fonctionnement totalement différent des composants passifs a été mis en exergue. Ce qui nous a conduit à les appliquer sur des structures périodiques. Cela a donné des résultats intéressants comme la propagation supraluminique sur une ligne de transmission des ondes. Et en les appliquant à la cellule unitaire d’une surface de métamatériaux qui est aussi une structure périodique, sa taille est réduite pour une plus grande compacité des antennes à cavités conçues pour les basses fréquences où la longueur d’onde est très grandeThe search of new materials has enabled new developments in recent decades. Among these are artificial or dielectric metamaterials. However, if these materials are passive, despite all the possible developments, the antennas performances or other structures resulting from them will still face the same fundamental limitations. By adding active circuits in these materials, such as negative resistors, negatives capacitors and negative inductors, it is possible to overcome these limitations and the synthesized properties and engineering applications can be significantly expanded. Indeed, this would create materials and devices with properties which can allow us to obtain behavior nonexistent in nature. This open the way to new applications. In this thesis, we explore the opportunity at first to use non-Foster circuits that are active feedback circuit, in the matching network of an electrically small antenna for low frequency operation. This helped to highlight its advantages over more conventional passive matching. Then, negative capacitors and negative and positive inductors were fabricated. Their totally different behaviors with passive components were also highlighted. This led us to apply them on periodic structures. Interesting results were obtained as superluminal wave propagation on a transmission line. And by applying to the unit cell of a metamaterial surface which is also a periodic structure, the size is reduced to a more compact cavity antennas designed for low frequency where the wavelength is very large
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Issiali, Khouloud. "Study of smart antennas and MU-MIMO techniques for indoor radio engineering and planning tools." Thesis, Rennes, INSA, 2015. http://www.theses.fr/2015ISAR0039/document.
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La facilité de déploiement et la flexibilité des technologies sans fil ont permis une évolution considérable des normes IEEE 802.11. L'arrivée de la fibre optique à la maison a également motivé des études de recherche pour accroître les débits et la capacité. Dans ce contexte, la dernière norme IEEE 802.11ac ratifiée en 2014 a normalisé de nouvelles technologies pour atteindre des débits maximaux au-dessus de 1Obit/s. En particulier, 802 llac propose le Multiple Input Multiple Output Multi-Utilisateurs (MIMO-MU) et le Transmit Beamforming (TxBF). Ces technologies d'antennes intelligentes supposent un diagramme d'antenne d'émission qui dépend de la position des utilisateurs et des caractéristiques du canal de propagation multi-trajets correspondant. Cependant, les outils d'ingénierie et de planification radio actuels simulent une carte de couverture fixe et indépendante de tout traitement d'antennes adaptatives côté émission. Cette thèse étudie l'impact de ces techniques MIMO-MU et TxBF et propose des solutions adaptées pour l'ingénierie radio et l'optimisation du système ainsi que pour les outils de planification radio. En effet, la première partie de cette thèse consiste à affiner les gains de capacité en identifiant les configurations et les paramètres système optimaux. La deuxième partie aborde les gains de beamforming en termes du gain sur le rapport signal à bruit (SNR) et sur la réduction du niveau d'interférence pour avoir une modélisation réaliste de la couverture radioThe deployment facility and flexibility of wireless technologies have allowed considerable evolution of IEEE 802 .11 standards. The arrival of the optical fiber to the home has further motivated the research studies to increase data rates and capacity. ln this context, the latest IEEE 802.l lac standard ratified in 2014 proposes new technologies to achieve maximum data rates above 1 Gbit/s. ln particular, 802.l lac includes the Multi-User Multiple Input Multiple Output (MU-MIMO) and Transmit Beamforming (TxBF). These smart antenna technologies assume a variable transmit antenna pattern in function of the users' position and the corresponding multipath propagation channel characteristics. However, the actual radio planning tools give a fixed coverage map in dependent of any adaptive or smart antenna processing. This thesis studies the impact of the MU-MIMO and TxBF techniques on radio engineering, system optimization as well as radio planning tools. Indeed, the first part of this thesis deals with refining the sum rate capacity gains by identifying interesting system configurations and optimal system parameters. The second part addresses the beamforming gains in terms of the Signal-to-Noise Ratio (SNR) gain and interference level to have realistic radio coverage modeling
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LOPES, DANIEL T. "Caracterização de estruturas de ondas lentas helicoidais para utilização em, TWT de potência." reponame:Repositório Institucional do IPEN, 2007. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11596.
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Made available in DSpace on 2014-10-09T12:53:40Z (GMT). No. of bitstreams: 0Made available in DSpace on 2014-10-09T13:58:44Z (GMT). No. of bitstreams: 0
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
Dissertação (Mestrado)
IPEN/D
Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP
FAPESP:05/03612-0
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Barksdale, Harry. "Millimeter wave scattering by rain in an antenna's near field." Diss., Virginia Polytechnic Institute and State University, 1988. http://hdl.handle.net/10919/53906.
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One of the important considerations in radio link analysis is the signal degradation that accompanies rainfall in a link’s path. Random scattering by rain can adversely affect a propagating wave in two ways. First, it results in attenuation and depolarization of the coherent field which is associated with the forward propagating wave. ln addition to this, random scattering gives rise to an incoherent field component that can further degrade the signal in a manner similar to multipath.
This dissertation presents an analysis of the coherent and incoherent effects of rain scatter at millimeter-wave frequencies. Within it, the scattering properties of individual spherical and non-spherical are quantified. Spherical raindrops are treated using the Mie theory and non-spherical ones analyzed with Waterman’s Extended Boundary Condition Method. Computed values of forward scattering amplitudes and scattering cross-sections for both spherical and non-spherical raindrops at 80, 45, 70 and 90 GHz are presented; the computer programs used to obtain the scattering data are also provided. Following the analysis of individual raindrops scatterers, the Foldy·Lax Twersky integral equations for coherent field and incoherent intensity are used to derive the coherent and incoherent outputs of a generic radio receiver. In doing so, the effects of scattering in an antenna’s far-field and radiating near field (Fresnel Region) are analyzed. Through this analysis, it is shown that the expected system outputs are essentially the same in either case.
Using the computed raindrop scattering parameters and models developed for the coherent and Incoherent system outputs, specific cases are Iooked at for 30, 45, 70 and 90 GHz operation and theoretical data presented. The data consists of the predicted attenuation and Isolation of the coherent signal and the ratio of coherent to Incoherent power In the presence of rain. From the latter it Is found that during heavy rainfall, the Incoherent effects can be appreciable and should be taken into account.Ph. D.
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Alves, Thierry. "Conception d'antennes pour le réseau BAN et modélisation du canal de propagation." Phd thesis, Université Paris-Est, 2011. http://tel.archives-ouvertes.fr/tel-00664279.
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Les études présentées dans cette thèse font l'objet d'un travail innovant concernant la conception des antennes pour les réseaux de type BAN et la modélisation des canaux associés. L'ouvrage de thèse est réparti en quatre chapitres. Deux chapitres sont consacrés à la modélisation de la propagation le long du corps où l'on montre que les formulations analytiques d'ondes de surface et d'ondes rampantes sont applicables dans ce contexte. L'effet des tissus adipeux est également pris en compte par le biais d'un modèle à trois couches (peau, graisse et muscle) et renseigne sur la variabilité du bilan de liaison suivant les personnes. Ce type de modélisation est le premier à inclure les formes du corps, les caractéristiques électriques des tissus biologiques et les caractéristiques de rayonnement des antennes. Une méthode basée sur l'autocorrélation du canal est également présentée afin de connaître les temps de cohérences des évanouissements lents et rapides. Par la suite, il est montré comment les évanouissements lents sont extraits par le biais d'un filtrage FFT fonction du temps de cohérence associé. L'étude des canaux se termine sur une série de mesures en chambre anéchoïde qui a permis de vérifier la validité des modèles analytiques. Des mesures en milieu indoor ont abouti à la proposition de plusieurs modèles statistiques basés sur une loi de Nakagami-m fonction de la distance sur le corps. Deux autres chapitres sont consacrés à la conception d'antennes à proximité de tissus biologiques et devant être intégrées dans des biocapteurs ou des vêtements. Pour cela, nous nous sommes particulièrement intéressés aux structures en F-inversé comme les IFA imprimées et les PIFA. Nous avons également réalisé des monopôles courts ayant un comportement de type magnétique. Nous montrons par le biais de simulations et de mesures sur un fantôme que seules les antennes du type monopôle et PIFA permettent une bonne excitation des ondes de surface. On montre par la suite l'influence du facteur de qualité d'une antenne sur son rendement et l'on en conclue qu'une antenne doit présenter un facteur de qualité faible pour avoir un bon rendement. La désensibilisation d'une antenne face au corps est également présentée. L'emploi de feuilles de ferrites aide à concentrer le champ réactif et limite ainsi les inévitables désadaptations dues au corps. Le coefficient de qualité joue également un rôle important dans le comportement de l'antenne face aux variabilités des tissus biologiques. L'estimation du rendement est un autre point difficile à réaliser lorsque les antennes sont sur le corps. Malgré tout nous proposons une nouvelle méthode que nous vérifions par simulation. Finalement, une structure à diversité est également proposée. Cette dernière tient compte des connaissances acquises au long de ce travail de recherche. Une sélection des meilleurs types d'antennes du point de vu canal et rendement est réalisée. La structure choisie est composée d'une PIFA et d'un monopôle court découplés par le biais de fentes λ/4. Des mesures in situ en milieu indoor donnent un gain en diversité maximum de 8.1 dB pour un schéma de type sélection
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Bellec, Mathilde. "Conception de systèmes antennaires omnidirectionnels et directifs favorisant les ondes de surface comme vecteur de propagation dans la bande HF." Thesis, Rennes 1, 2015. http://www.theses.fr/2015REN1S142.
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Les ondes de surface se propagent le long de la surface terrestre par-delà l'horizon et ces propriétés de propagation sont des atouts pour diverses applications industrielles (civiles ou militaires) opérant dans la bande HF. C'est le cas notamment des radars transhorizon, des systèmes de communications, de la détection de tsunami, ou encore l'étude de la courantologie. Actuellement, les aériens utilisés dans ce contexte ne sont pas optimisés pour privilégier la propagation par ondes de surface. C'est dans ce contexte que TDF, la Direction Générale de l'Armement (DGA) et l'Institut d'Electronique et de Télécommunications de Rennes (IETR) se sont associés pour proposer cette thèse. L'objectif principal de la thèse est de concevoir des antennes en bande HF de dimensions réduites (<3 mètres) réduisant le rayonnement vers le ciel afin favoriser l'onde de surface. Une première approche a permis de concevoir deux antennes élémentaires, l'une omnidirectionnelle et l'autre directive, permettant de réduire le rayonnement vers le ciel pour les sites compris entre -45° et +45°. Les solutions proposées sont de tailles très réduites grâce à l'utilisation d'une antenne à polarisation verticale électriquement courte dans le plan vertical et de parasites horizontaux alimentés par couplage EM. Les études expérimentales réalisées à échelle réelle sont en bon accord avec les performances théoriques obtenus à l'aide de logiciels d'analyse électromagnétique commerciaux. Une seconde approche a permis de concevoir des réseaux d'antennes électriquement courtes dans le plan vertical selon une disposition linéaire des aériens. La réduction du rayonnement vers le ciel est réalisée grâce aux réseaux de type Endfire/Broadside. Enfin, une troisième étude a permis de concevoir deux systèmes antennaires agiles en diagrammes tout en conservant les propriétés de réduction de rayonnement vers le ciel. Le premier système à l'aide d'antennes électriquement courtes dans le plan vertical chargées par des réactances, et le second en appliquant une pondération en amplitude et en phase d'un réseau à deux dimensionsThe surface-waves propagate beyond the horizon. This phenomenon is an attractive feature for many applications operating in the HF band both in civil or military field. By example, we can quote the High Frequency Surface Waves Radar (HFSWR), communicating systems, or the study of the currentology. Currently, the antennas used in the field of surface-waves propagation are not fully optimized and radiate also in sky wave. In order to optimize the radiation pattern of the antennas used in these systems, the company TDF, the Direction Générale de l’Armement (DGA) and the Institute of Electronic and Telecommunications of Rennes (IETR) have proposed this projetct. The main objective of this work is to design electrically small antennas in the vertical plane (< 3 meters) in the HF band while reducing the radiation toward the sky. The first concept is based on vertically polarized antennas electrically small in the vertical plane coupled to horizontally radiators placed above the antenna. As a result, the radiation pattern in the horizontal plane is omnidirectional or directive with a radiation toward the sky reduced for the elevations range from -45° to +45°. Prototypes have been realized and validated by measurements. Then, in the second study we have developed antennas array in order to reduce the radiation toward the sky with another way that the horizontal radiators. This method allows reducing significantly the radiation toward the sky according to the number of elements in the array. Finally, in the third study we have studied electronically scanning antennas while maintaining the reduction of the radiation toward the sky. The first system is based on an array of radiator loaded by reactance, and the second is based on a planar array with an appropriate feeding
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Adjali, Imad. "Approche statistique pour la quantification des performances d'antennes fortement couplées : application à la RFID dans le contexte d'une densité élevée de tags." Thesis, Paris Est, 2020. http://www.theses.fr/2020PESC2011.
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Cette thèse se place dans un contexte applicatif spécifique de la RFID (Radio Frequency Identification) UHF (Ultra-High Frequency) pour lequel un grand nombre de tags RFID est concentré dans un volume réduit. Ce contexte conduit à des configurations pour lesquelles les antennes associées aux tags sont fortement couplées. Dans ces conditions de fort couplage et de forte densité de tags, une antenne peut voir son impédance d’entrée désadaptée et son diagramme de rayonnement distordue. La conséquence de cette diminution des performances de l’antenne tag est la réduction globale du taux de lecture des tags liée à la dégradation du bilan de liaison individuel entre certains tags et l’antenne lecteur. Afin d’appréhender ce problème fortement aléatoire du fait de la distribution à priori inconnue des tags, il est nécessaire de développer une méthode statistique robuste. Pour atteindre des temps de simulation raisonnables malgré un grand nombre de réalisations de distributions aléatoires de tags, l’approche choisie dans cette thèse est de modéliser les antennes tags et le couplage entre antennes par des antennes dipôles grâce à des modèles analytiques basés sur la méthode IEMF. Ces dipôles peuvent être chargés sur des impédances adaptées ou non pour s’approcher du cas réel d’antennes tags chargées par l’impédance d’entrée des puces RFID. Les modèles analytiques sont validés par des méthodes numériques et des mesures. Les analyses statistiques des données concernent la désadaptation en impédance et le gain dans la direction du lecteur. Des analyses statistiques sont également effectuées sur des simulations de tags commerciaux avec une corrélation satisfaisante avec les résultats de dipôles. A terme, ce travail de thèse portant sur le « comportement de groupe » d’antennes doit fournir les outils d’analyse et de synthèse nécessaires pour évaluer la robustesse d’un design d’antenne RFID dans un environnement proche caractérisé par une forte densité de tags et un fort couplageThis context of this thesis is that of UHF RFID use cases where a large number of RFID tags is concentrated in a limited volume. This context leads to scenarios in which the tag antennas can be strongly coupled electromagnetically. Under the conditions of high coupling and high density of tags, an antenna can be mismatched and its radiation pattern distorted. As a result of the antenna’s loss of performance, a global reduction of the tags reading rate can be observed as well as a drop of the reading distance for some of the tags. In order to tackle this highly random problem flowing from the unknown distribution of tags, the approach developed in this work is to assume that the electromagnetic coupling between antennas can be modeled by analytical formulas of self and mutual impedances valid for straight resonant dipoles. These dipoles can be loaded by complex impedances corresponding to the chip input impedances of real commercial RFID tags. The analytical models are validated by numerical simulations and experimental results. Statistical studies are performed for a large number of dipole distributions in terms of impedance mismatch and embedded gain variations in the direction of the reader. A statistical analysis of simulated commercial tags is also performed showing a good correlation with the dipole statistics. In the future, this work on the “group behavior” of antennas should provide the analysis and synthesis tools required for a robust evaluation of the tag performances in an environment characterized by a high tag density
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Garcia, Pardo Concepción. "Experimental characterization of the radio channel for systems of large bandwidth and multiple antennas." Thesis, Lille 1, 2012. http://www.theses.fr/2012LIL10014/document.
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La généralisation des nouvelles applications des communications sans fil nécessitera dans un avenir proche des communications très haut débit qui avoisineront 1Gb/s. Une des solutions proposées pour répondre à cette demande est basée sur l’utilisation de réseaux d’antennes à l’émission et à la réception connue sous la terminologie Multiple-Input Multiple-Output (MIMO). Plus récemment, les techniques ultra large bande (ULB) ont connu un regain d’intérêt grâce aux débits très élevés qu’offre sa grande bande passante et les faibles puissances d’émission mises en jeux. Si on envisage l’association de ces deux techniques au sein même d’un système, il est nécessaire, lors de l’optimisation de la chaîne de communication, de connaître au préalable les caractéristiques du canal radio. L’objectif de cette thèse porte sur la caractérisation expérimentale multidimensionnelle (MD) du canal radio pour des communications en milieux confinés. L’intérieur des bâtiments et le tunnel ferroviaire seront deux exemples traités dans cette étude. Précisons que la demande de haut débit en tunnel ferroviaire concerne les communications multimédia pour des applications de vidéo surveillance et de contrôle commande. Les travaux originaux menés au cours de cette thèse ont porté sur :- Le développement d’un sondeur de canal MIMO large bande permettant une caractérisation directe dans le domaine temporel. - La caractérisation (MD) en polarisation croisée du canal de propagation à l’intérieur d’un bâtiment et en tunnel. - l’analyse phénoménologique de la technique de retournement temporel et des diversités de polarisation, fréquentielle et d’espace appliquées aux communications en tunnelRecent and future wireless applications require large data rates. Multiple-Input Multiple-Output (MIMO) systems were proposed as one solution to achieve higher spectral efficiency. More recently Ultra-Wideband (UWB) systems, have gained interest owing its extremely high data rates. However, precise knowledge of the radio channel is an essential issue to design the global system and, thus to reach such improvement in the performances of wireless communications. This thesis is mainly focused on the experimental characterization of the radio channel for systems with large bandwidth and MIMO. In general, most of the research on MIMO and UWB are performed in indoor environments. However, there are other scenarios where reliable communications are also needed, for example, in tunnels. In this special environment, there is an increasing necessity of developing and implementing control/command equipment, in order to develop safe and efficient trains and infrastructures. Thus, the objectives pursued in this thesis are:- Improve an existing frequency-domain MIMO channel sounder to achieve more enhanced capabilities.- Develop a wideband time-domain MIMO channel sounder in order to perform measurements directly in the time-domain.- Characterize the MIMO-UWB radio channel in office environment by means of measurements carried out in the underground level of the Universidad Politécnica de Cartagena. Multi dimensional channel parameters have been deduced from numerous measurement campaigns.- Study the propagation in tunnels and give physical interpretation of the performances of space, frequency and polarization diversity, and of time reversal techniques
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El, Masri Ihsan. "Caractérisation électromagnétique du canal de propagation sur silicium : applications aux interconnexions sans fils intra-puce pour les systèmes WiNoC Electromagnetic characterization of the intrachip propagation channel in Ka - and V -Bands, in IEEE Transactions on Components, Packaging and Manufacturing Technology 9 (10), October 2019." Thesis, Brest, 2019. http://www.theses.fr/2019BRES0060.
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À l'ère de l'intelligence artificielle, de Big Data et de l'Internet des Objets, le développement des NoC est devenu une priorité. Dans le cadre du projet BBC, nous avons opté pour les interconnexions WiNoC, qui assurent les besoins de communications efficaces au niveau intra-puce (latence faible, débit élevé, efficacité énergétique minimale, compatibilité avec la technologie CMOS, adaptabilité pour le broadcast).Cette thèse se concentre sur l’étude électromagnétique la couche physique de WiNoC, et particulièrement sur la caractérisation des canaux de propagation sur des substrats silicium. Dans ce contexte, nous mettons en évidence au travers de simulations et de mesures en bandes Ka et V, les problèmes de la propagation à très hautes fréquences dans des structures sur Si (cavités, ondes de surface et trajets multiples). Par la suite, nous proposons une solution permettant de limiter ces problèmes dus aux réflexions sur les interfaces Si/Air en ajoutant une couche absorbante autour du substrat. Nous montrons à l’aide de simulations et de mesures en bandes Q et V, l’amélioration de la transmission et l’élargissement des bandes passantes. Dans le but de réduire la taille des antennes et d'augmenter le débit, nous étudions dans la bande Sub-THz des réseaux de monopoles intégrés dans un substrat Si placé entre deux plaques métalliques.Finalement, nous estimons les performances et nous montrons la possibilité de transmettre au moins 12 Gbps sur une portée de 21,2 mm et avec une efficacité énergétique de l’ordre de 4,5 pJ/bit. Ces résultats sont comparables avec les solutions concurrentes (WiNoC, RF guidées, optiques)In the age of artificial intelligence, Big Data and the Internet of Things, the development of NoCs has become a priority. As part of the BBC project, we have opted for WiNoC interconnects, which provide efficient communication requirements at the intra-chip level (low latency, high throughput, minimal energy efficiency, compatibility with CMOS technology, adaptability for broadcast).This thesis focuses on the electromagnetic study the physical layer of WiNoC, and particularly on the characterization of propagation channels on silicon substrates.In this context, we highlight, through simulations and measurements in Ka and V bands, the problems of propagation in Si structures at very high frequency (cavities, surface waves and multiple paths).Subsequently, we propose a solution to limit these problems (due to reflections on the Si / Air interfaces) by adding an absorbing layer around the substrate. Using simulations and measurements in Q and V bands, we show improved transmission with a large bandwidth (>16 GHz).In order to reduce the size of the antennas and to increase the data rate, we study in the Sub-THz band, networks of monopoles embedded in a Si substrate placed between two metal plates.Finally, we estimate the performance and we show the possibility of transmitting at least 12 Gbps over a range of 21.2 mm and with an energy efficiency of the order of 4.5 pJ / bit. These results are comparable with competing solutions (WiNoC, RF interconnects, optical interconnects)
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Farouq, Mohamed. "Transformation de front d'ondes par des méthodes matricielles." Thesis, Paris 11, 2015. http://www.theses.fr/2015PA112222/document.
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La caractérisation des sources de rayonnement électromagnétique par des techniques de champ proche est aujourd'hui largement utilisée. Ces techniques consistent à mesurer le champ rayonné à proximité de la source pour en déduire, par traitement mathématique, le champ dans d'autres zones de l'espace (champ proche ou champ lointain). Les applications sont nombreuses comme par exemple la caractérisation des diagrammes de rayonnement des antennes ou la détermination des périmètres de sécurité autour des antennes de station de base. Par ailleurs, la mesure en champ proche trouve également des applications dans le diagnostic des sources.Ce travail de thèse porte sur une nouvelle méthode de calcul des coefficients du développement modal à partir d'une mesure sur une surface échantillonnée irrégulièrement ou arbitraire. Ces coefficients permettent ensuite d'évaluer le diagramme de rayonnement de la structure rayonnante dans toutes les directions de l'espace.Le principe de la méthode matricielle consiste à mesurer les composantes tangentielles du champ électromagnétique sur une surface. Les coefficients modaux sont obtenus par l'inversion d'un système d'équations linéaires reliant le champ électrique mesuré et les fonctions d'ondes.Cette méthode permet de désolidariser la géométrie de la surface de mesure du système de coordonnées dans lequel est exprimé le développement modal. Il en résulte de nombreux avantages, comme le choix d'une surface de mesure quelconque, pour des raisons de compacité, de simplicité de mise en œuvre ou de suppression d'erreur de troncatureThe characterization of electromagnetic radiation sources by near field techniques is now widely used. These involve measuring the radiated field close to the source to deduce, by mathematical processing, the field in other areas of space (near field and far field). There are many applications such as the evaluation of the antenna far field radiation patterns or the determination of safety perimeters around base station antennas. Furthermore, the near-field measurement technique can be used in the sources diagnostic.In our study, we present a new method for calculating the modal expansion coefficients from irregularly sampled or arbitrary measurement surfaces. The calculation of these modal coefficients allows the assessment of the radiation pattern of the antenna under test in every spatial directions.The principle of the matrix method is to calculate the modal coefficients by solving a system of linear equations relating the measured electric field and wave functions. Once the modal coefficients are known the far field of the structure is achieved.This method allows the separation between the geometry of the measuring surface and the coordinate system wherein the modal expansion is expressed. This leads to many advantages, such as selecting any measurement surfaces, for the reasons of compactness, implementation simplicity or truncation errors suppression
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Forsberg, Nicklas, and Johan Säfholm. "Radioräckviddsberäkningar för flygande plattformar." Thesis, Linköping University, Department of Electrical Engineering, 2002. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-1080.
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There exist several known methods for calculation of radio coverage for ground-based systems. As far as we know there are no equivalent methods for the case of flying platforms when the altitudes and speeds are significantly different to those of ground-based systems.
This thesis describes the theoretical concepts behind calculations of radio coverage for flying platforms. An investigation is made to sort out what is important and possible to employ in a model for simulations. A method is described and implemented in a program for evaluation of flying radio systems. Two typical cases of flight missions are simulated and discussed.
It is found that the free space model is valid most of the mission time. The contribution from the antennas is found to be small in comparison to the path loss. Further investigations suggested are e.g. better ground reflection models and a better model for the flight mechanics.
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Mhedhbi, Meriem. "Contribution to deterministic simulation of Body area network channels in the context of group navigation and body motion analysis." Thesis, Rennes 1, 2015. http://www.theses.fr/2015REN1S049/document.
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Les progrès récents dans les technologies et les systèmes de communications sans fil soutenus par la miniaturisation de dispositifs ont donné naissance une nouvelle génération de réseaux personnels permettant des communications autour du corps humain: les réseaux corporels. Cette thèse étudie les différents types du canal de propagation des réseaux corporels en environnement intérieur dans le contexte de l’analyse du mouvement et de la navigation de groupe. Dans ce travail, une approche de simulation pour le cala de propagation est présenté. Le simulateur de canal de propagation est basé sur les techniques de tracé de rayons et l’approche de simulation est basée sur l’utilisation d’antennes perturbées et l’utilisation des données de capture de mouvement pour la modélisation de la mobilité humaine. Premièrement, nous étudions la question de l’antenne et l’influence de la proximité du corps humain sur diagramme de rayonnement de l’antenne. En outre, un modèle simple utilisé pour prédire le diagramme de rayonnement d’une antenne placée à proximité d’un corps humain. Deuxièmement, le simulateur physique est présenté et l’approche de simulation est introduite. Afin de vérifier l’approche proposée, des simulations préliminaires ont été effectuées et une première comparaison avec des donnes de mesures disponibles est faite. Enfin, une campagne de mesure spécifique joignant les données radio et les données de capture de mouvement a été exploitée pour valider et évaluer les résultats de la simulationRecent advances in wireless technologies and system, empowered by the miniaturization of devices, give rise to a new generation of Personal Area Networks allowing communications around the human body : Body Area networks. This thesis studies the Body Area Network channels in indoor environment in the context of motion analysis and group navigation. In this work a simulation approach for BAN channels is presented. The propagation channel simulator is based on ray tracing and the simulation approach is based on using perturbed antennas and the use of motion capture data for modelling the human mobility. Firstly, we investigate the antenna issue and the influence of the human body prox- imity on antenna radiation pattern. Besides, a simple model used to predict the antenna radiation pattern placed in proximity to a human body. Secondly, the physical sim- ulator is presented and the simulation approach is introduced. In order to check the proposed approach, preliminary simulations were carried out and a first comparison with available measurement data is made. Finally, a specific measurement campaign jointing radio data and motion capture data was exploited to validate and evaluate the simulation results
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Vincent, Julien. "Modélisation d’antennes basses fréquences en présence de sol et d’environnements réalistes." Phd thesis, Toulouse, INPT, 2015. http://oatao.univ-toulouse.fr/14162/1/vincent.pdf.
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Ce travail de thèse traite les domaines du rayonnement d'antennes basses fréquences et de la propagation du champ électromagnétique, en présence du sol et d'environnement réalistes. Des éléments qui diffèrent du cas canonique du sol plan homogène et infini sont considérés par le mot "réalistes". Les méthodes numériques classiques pour l'électromagnétisme, en particulier pour la modélisation du rayonnement d'antennes, sont plutôt adaptées à des fréquences au-delà des hautes fréquences et au rayonnement en espace libre. Deux axes de recherche ont été définis comme suit: les effets d'environnements situés en zone proche sur le rayonnement d'antennes filaires basses fréquences et l'étude de systèmes éloignés de la source par la création d'une méthode hybride. En ce qui concerne le rayonnement en zone proche, une méthode des différences finies dans le domaine temporel est utilisée. Celle-ci est lourde d'un point de vue des temps de calculs et de l'occupation de la mémoire, cependant elle est effective du fait du maillage volumique de la scène. Dans le cas de la propagation lointaine, la solution parfaite du rayonnement d'un dipôle infinitésimal électrique vertical au-dessus d'un sol plan homogène infini a été traitée par la création d'un algorithme adaptatif d'intégration numérique. Ce dernier permet d'obtenir les valeurs du champ électromagnétique dans tout l'espace avec une précision numérique contrôlée. Une technique originale d'hybridation a été réalisée entre l'algorithme d'intégration et la méthode des différences finies pour rendre compte efficacement des effets d'éléments lointains sur la propagation du champ.
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Kouassi, Attibaud. "Propagation d'incertitudes en CEM. Application à l'analyse de fiabilité et de sensibilité de lignes de transmission et d'antennes." Thesis, Université Clermont Auvergne (2017-2020), 2017. http://www.theses.fr/2017CLFAC067/document.
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De nos jours, la plupart des analyses CEM d’équipements et systèmes électroniques sont basées sur des approches quasi-déterministes dans lesquelles les paramètres internes et externes des modèles sont supposés parfaitement connus et où les incertitudes les affectant sont prises en compte sur les réponses par le biais de marges de sécurité importantes. Or, l’inconvénient de telles approches est qu’elles sont non seulement trop conservatives, mais en outre totalement inadaptées à certaines situations, notamment lorsque l’objectif de l’étude impose de prendre en compte le caractère aléatoire de ces paramètres via des modélisations stochastiques appropriées de type variables, processus ou champs aléatoires. Cette approche probabiliste a fait l’objet ces dernières années d’un certain nombre de recherches en CEM, tant au plan national qu’au plan international. Le travail présenté dans cette thèse est une contribution à ces recherches et a un double objectif : (1) développer et mettre en œuvre une méthodologie probabiliste et ses outils numériques d’accompagnement pour l’évaluation de la fiabilité et l’analyse sensibilité des équipements et systèmes électroniques en se limitant à des modélisations stochastiques par variables aléatoires ; (2) étendre cette étude au cas des modélisations stochastiques par processus et champs aléatoires dans le cadre d’une analyse prospective basée sur la résolution de l’équation aux dérivées partielles des télégraphistes à coefficients aléatoires.L’approche probabiliste mentionnée au point (1) consiste à évaluer la probabilité de défaillance d’un équipement ou d’un système électronique vis-à-vis d’un critère de défaillance donné et à déterminer l’importance relative de chacun des paramètres aléatoires en présence. Les différentes méthodes retenues à cette fin sont des adaptations à la CEM de méthodes développées dans le domaine de la mécanique aléatoire pour les études de propagation d’incertitudes. Pour le calcul des probabilités de défaillance, deux grandes catégories de méthodes sont proposées : celles basées sur une approximation de la fonction d’état-limite relative au critère de défaillance et les méthodes de Monte-Carlo basées sur la simulation numérique des variables aléatoires du modèle et l’estimation statistique des probabilités cibles. Pour l’analyse de sensibilité, une approche locale et une approche globale sont retenues. Ces différentes méthodes sont d’abord testées sur des applications académiques afin de mettre en lumière leur intérêt dans le domaine de la CEM. Elles sont ensuite appliquées à des problèmes de lignes de transmission et d’antennes plus représentatifs de la réalité.Dans l’analyse prospective, des méthodes de résolution avancées sont proposées, basées sur des techniques spectrales requérant les développements en chaos polynomiaux et de Karhunen-Loève des processus et champs aléatoires présents dans les modèles. Ces méthodes ont fait l’objet de tests numériques encourageant, mais qui ne sont pas présentés dans le rapport de thèse, faute de temps pour leur analyse complèteNowadays, most EMC analyzes of electronic or electrical devices are based on deterministic approaches for which the internal and external models’ parameters are supposed to be known and the uncertainties on models’ parameters are taken into account on the outputs by defining very large security margins. But, the disadvantage of such approaches is their conservative character and their limitation when dealing with the parameters’ uncertainties using appropriate stochastic modeling (via random variables, processes or fields) is required in agreement with the goal of the study. In the recent years, this probabilistic approach has been the subject of several researches in the EMC community. The work presented here is a contribution to these researches and has a dual purpose : (1) develop a probabilistic methodology and implement the associated numerical tools for the reliability and sensitivity analyzes of the electronic devices and systems, assuming stochastic modeling via random variables; (2) extend this study to stochastic modeling using random processes and random fields through a prospective analysis based on the resolution of the telegrapher equations (partial derivative equations) with random coefficients. The first mentioned probabilistic approach consists in computing the failure probability of an electronic device or system according to a given criteria and in determining the relative importance of each considered random parameter. The methods chosen for this purpose are adaptations to the EMC framework of methods developed in the structural mechanics community for uncertainty propagation studies. The failure probabilities computation is performed using two type of methods: the ones based on an approximation of the limit state function associated to the failure criteria, and the Monte Carlo methods based on the simulation of the model’s random variables and the statistical estimation of the target failure probabilities. In the case of the sensitivity analysis, a local approach and a global approach are retained. All these methods are firstly applied to academic EMC problems in order to illustrate their interest in the EMC field. Next, they are applied to transmission lines problems and antennas problems closer to reality. In the prospective analysis, more advanced resolution methods are proposed. They are based on spectral approaches requiring the polynomial chaos expansions and the Karhunen-Loève expansions of random processes and random fields considered in the models. Although the first numerical tests of these methods have been hopeful, they are not presented here because of lack of time for a complete analysis
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Fuscaldo, Walter. "Advanced radiating systems based on leaky waves and nondiffracting waves." Thesis, Rennes 1, 2017. http://www.theses.fr/2017REN1S015/document.
Full textAbstract:
La focalisation du champ électromagnétique dans les zones de champ proche et lointain est un sujet de forte actualité pour l'imagerie médicale et la radiométrie des microondes jusqu'aux ondes millimétriques. Dans ce cadre, la théorie des ondes de fuite est un formalisme élégant qui permet de décrire d'une même façon les problèmes radiatifs en champ proche et en champ lointain des microondes aux fréquences optiques. Dans cette thèse, on utilise la polyvalence de la théorie des ondes de fuite pour développer des systèmes rayonnants complexes afin de contrôler les caractéristiques radiatives en champ lointain aux fréquences submillimétriques et pour focaliser la radiation électromagnétique en champ proche aux fréquences millimétriques. Ainsi, l'utilisation de matériaux uniques comme le graphène et les cristaux liquides ont été considérés pour la conception des antennes à ondes de fuite, en obtenant des résultats très intéressants en termes de reconfigurabilité, d'efficience et de directivité. Dans ce contexte, une analyse théorique originale a fourni de nouvelles formules pour l'évaluation des caractéristiques radiatives (c.à.d. la largeur de faisceau, le niveau des lobes secondaires, etc.) des antennes à ondes de fuite. En effet, la largeur du faisceau de ces antennes est, jusqu'à présent, estimée au moyen des formules proposées pour la première fois dans les années '60 par Prof. Arthur A. OLINER. Ces formules ne tiennent en compte ni de la longueur de l'antenne (sauf pour des cas très particuliers), ni du rayonnement longitudinal, elles ne permettent donc pas une évaluation rigoureuse.En complément à la reconfigurabilité en champ lointain, les ondes de fuite offrent aussi la possibilité de focaliser la radiation en champ proche. Dans ce cas, on voit que les ondes de fuite peuvent être utilisées d'une façon efficace pour générer des faisceaux non diffractifs de Bessel à travers des systèmes rayonnants à bande étroite aux ondes millimétriques. De plus, le caractère non diffractif des faisceaux de Bessel peut aussi être utilisé pour générer des impulsions très localisées (comme les solitons en optiques) à travers la superposition continue des faisceaux de Bessel sur une large bande de fréquence. Dans ce cadre, une nouvelle formulation a été développée afin de comprendre les limitations physiques et technologiques concernant la génération des impulsions non diffractives et non dispersives, c.à.d. les X-waves. Les résultats ont montré qu'un type de systèmes rayonnants à large bande, notamment les antennes RLSA (en anglais « Radial Line Slot Array »), semblent très favorables pour la génération des X-wavesIn recent years, microwave, millimeter-wave, and THz applications such as medical and security imaging, wireless power transfer, and near-field focusing, just to mention but a few, have gained much attention in the area of ICT due to their potentially high social impact. On one hand, the need of highly-directive THz sensors with tunable radiating features in the far-field region has recently boosted the research activity in the design of flexible, low-cost and low-profile devices. On the other hand, it is of paramount importance to focus energy in the near-field region, and thus the generation of limited-diffraction waves in the microwave and millimeter-wave regime is a topic of recent increasing interest. In this context, leaky-wave theory is an elegant and extremely useful formalism which allows for describing in a common fashion guiding and radiating phenomena in both the near field and the far field, spanning frequencies from microwaves to optics passing through THz. In this PhD thesis we aim to exploit the intrinsic versatility of the leakywave approach to design advanced radiating systems for controlling the far-field radiating features at THz frequencies and for focusing electromagnetic radiation in the near field at millimeter waves. Specifically, the use of relatively new materials such as graphene and liquid crystals has been considered for the design of leaky-wave based radiators, achieving very promising results in terms of reconfigurability, efficiency, and radiating capabilities. In this context, an original theoretical analysis has provided new general formulas for the evaluation of the radiating features (e.g., half-power beamwidth, sidelobe level, etc.) of leaky-wave antennas. Indeed, the current formulations are based on several simplifying hypotheses which do not allow for an accurate evaluation of the beamwidth in different situations. In addition to the intriguing reconfigurable capabilities offered by leaky waves in far-field applications, interesting focusing capabilities can be obtained in the near field. In particular, it is shown that leaky waves can profitably be used to generate limited-diffraction Bessel beams by means of narrow-band radiators in the microwave range. Also, the use of higherorder leaky-wave modes allows for achieving almost the same performance in the millimeter-wave range, where previous designs were subjected to severe fabrication issues. Even more interestingly, the limited-diffractive character of Bessel beams can also be used to generate limited-diffraction pulses as superpositions of monochromatic Bessel beams over a considerable fractional bandwidth. In this context, a novel theoretical framework has been developed to understand the practical limitations to efficiently generate limited-diffraction, limited-dispersion pulses, such as X-waves, in the microwave/millimeter-wave range. As a result of this investigation, a class of wideband radiators has been thoroughly analyzed, showing promising capabilities for the generation of both zeroth-order and higher-order Xwaves. The latter may pave the way for the first localized transmission of orbital angular momentum in the microwave range
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Zemba, Michael J. "Site Characterization of Phase Instability via Interferometer Measurement." University of Akron / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=akron1383565461.
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Panahandeh, Ali. "Multi-polarized sensing for cognitive radio." Doctoral thesis, Universite Libre de Bruxelles, 2012. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209586.
Full textAbstract:
In this thesis the multi-polarized Cognitive Radios are studied. Cognitive Radios are proposed as an interesting way to more efficiently use the frequency resources. A Cognitive Radio secondary user finds the frequency bands which are not utilized by primary users and communicates on them without interfering with the primary users. In order to achieve this goal the secondary user must be able to detect reliably and quickly the presence of a primary user in a frequency band. In this thesis, the impact of polarization on the spectrum sensing performances of cognitive radio systems is studied.First the depolarization occurring in the wireless channel is studied for two cognitive radio scenarios. This is done through an extensive measurement campaign in two outdoor-to-indoor and indoor-to-indoor scenarios where the parameters characterizing the radiowaves polarization are characterized at three different spatial scales: small-scale variation, large-scale variation and distance variation.
Second, a new approach is proposed in modeling of multi-polarized channels. The polarization of received fields is characterized from an electromagnetic point of view by modeling the polarization ellipse. Theoretical formulations are proposed in order to obtain the parameters characterizing the polarization ellipse based on the signals received on three cross-polarized antennas. A system-based statistical model of the time-dynamics of polarization is proposed based on an indoor-to-indoor measurement campaign. The analytical formulations needed in order to project the polarization ellipse onto a polarized multi-antenna system are given and it is shown how the model can be generated.
Third, the impact of polarization on the spectrum sensing performances of energy detection method is presented and its importance is highlighted. The performance of spectrum sensing with multi-polarized antennas is compared with unipolar single and multi-antenna systems. This analysis is based on an analytical formulation applied to the results obtained from the multi-polarized measurement campaign. The detection probability as a function of distance between the primary transmitter and the secondary terminal and the inter-antenna correlation effect on the spectrum sensing performance are studied.
An important limitation of energy detector is its dependence on the knowledge of the noise variance. An uncertainty on the estimation of the noise variance considerably affects the performance of energy detector. This limitation is resolved by proposing new multi-polarized spectrum sensing methods which do not require any knowledge neither on the primary signal nor on the noise variance. These methods, referred to as “Blind spectrum sensing methods”, are based on the use of three cross-polarized antennas at the secondary terminal. Based on an analytical formulation and the results obtained from the measurement campaign, the performances of the proposed methods are compared with each-other and with the energy detection method. The effect of antenna orientation on the spectrum sensing performance of the proposed methods and the energy detection method is studied using the proposed elliptical polarization model.
Doctorat en Sciences de l'ingénieur
info:eu-repo/semantics/nonPublished
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Narrainen, Jessen. "Perforance evaluation of vehicle radiofrequency communication systems : contribution to the modelling approach." Thesis, Rennes, INSA, 2017. http://www.theses.fr/2017ISAR0007/document.
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Le cadre général de cette thèse porte sur les communications véhicule à véhicule (V2V). L'objectif principal de ce type de communication est d'améliorer la sécurité routière et d'optimiser la fluidité du trafic. Les performances de systèmes de communication embarqués dépendent principalement de la configuration des antennes, du type de récepteurs utilisés (modem) et du canal de propagation. Le sujet de la thèse se concentre précisément sur l'élaboration d'un outil de simulation robuste et fiable pour optimiser les choix technologiques d'antennes et leurs implantations à bord. Il permettra de limiter ainsi le recours aux prototypes et aux essais de roulage. Dans un premier temps, nous avons proposé une méthode de type géométrique-stochastique pour modéliser des canaux de propagation d'un système de communication V2V. Cette méthode permet de définir des scénarios dynamiques et sa flexibilité nous offre l'opportunité de paramétrer les caractéristiques d'un canal de propagation. Nous montrons pour l'essentiel de quelle manière l'agencement et le nombre de diffuseurs de forme simple peuvent contribuer à influencer les statistiques de l'étalement des retards, la distribution des angles d'arrivée et les spectres Doppler. Dans la deuxième partie de ces travaux, nous nous focalisons sur la problématique d'intégration d'antenne. Il a été constaté qu'il est particulièrement utile de simplifier la maquette numérique du véhicule complet lors d'une simulation électromagnétique de l'antenne intégrée à bord de ce véhicule. De plus, dans cette section, nous avons étudié la limite de la validité de substitution d'une antenne intégrée à bord par son seul diagramme de rayonnement dans les modèles de canaux de propagation. A partir de cette étude, nous en avons déduit, que les interactions électromagnétiques avec les éléments se situant dans le champ-proche n'étaient plus valides. Ainsi, une stratégie de correction a été trouvée en considérant l'élément en champ proche dans la simulation initiale de l'antenne intégrée sur le véhicule. L'évaluation des performances d'antennes, en termes de taux d'erreurs paquet, après l'implémentation de la couche physique du standard 802. 11 p, est au cœur de la troisième partie de cette thèse. Des résultats de simulation, pour chaque configuration d'antenne, ont été donnés pour plusieurs combinaisons de paramètres de couche PHY tels que le débit et la longueur de paquet. La dernière partie de ce manuscrit traite de la présentation d'une campagne de mesure qui a été réalisée principalement dans un environnement de type rural. Les essais de roulage avaient pour but de démontrer la capacité des méthodes de simulation à faire un choix approprié d'installation d'antenne. Nous avons constaté que les tendances attendues des performances de communication en termes de PER sont globalement prévisibles à partir de notre modèle bien que nous ayons obtenu des résultats surprenants dans certains cas. Ce qui nécessitera une enquête plus approfondieThe general framework of this Ph.D. thesis deals with Vehicle to Vehicle (V2V) communications. This communication is principally dedicated to reinforce security through exchange of information between vehicles in case of unexpected events. The development of V2V solutions requires the understanding and merging of a number of techniques from several communication technology areas. Indeed, the performance of these systems are related to three main blocks: the implementation of the modems, the antenna configuration and the fast varying electromagnetic environment surrounding the transmitter and the receiver. The purpose of this PhD thesis is precisely to elaborate a design strategy to investigate all the different blocks constituting the communication chain. The ultimate goal is to optimize antenna selection and location on board the vehicle. In the first place, we proposed a geometry-based stochastic channel modelling approach to develop virtual dynamic scenarios. It was shown that the most common propagation environments such as rural, highway or urban-like propagation channels are reached through adjustment or numbers and location of simple metallic plates. Using this method, we are able to emulate the characteristics, such as the delay spread, angles of arrival distribution and the Doppler spectrum, of these typical driving scenarios. Moreover, we dealt with antenna integration problems in the second part of this work. A study on the simplification of numerical models of vehicles was carried out. Furthermore in this section, we investigated the limit of validity of representing the integrated antenna on board vehicle solely by its radiation pattern. We deduced from this study that the interactions with the elements present in the near-field is no longer valid. Thus, a strategy to alleviate the degree of error was found upon consideration of the near-field scatter in the a-priori simulation of the antenna integrated on the vehicle. In the third part of this thesis, we evaluated the performance of different antenna configurations in terms of packet error rate after the embodiment of the PHY layer of the LEEE 802.11p standard. Simulation results, for each antenna configurations, was given for several combinations of PHY layer parameters such as data rate and packet length. The last part of this manuscript is dedicated to the presentation of a measurement campaign that was carried out in a rural driving environment. Results obtained from these functional tests were confronted with simulation results to demonstrate the strength of the latter. We found that the expected trends in communication performance in terms of PER are globally predictable from our model though we obtained surprising results in some cases, needing further investigation
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Donzelli, Valderez de Almeida. "Polarização elíptica: influência no desempenho de cobertura da TV digital." Universidade Presbiteriana Mackenzie, 2011. http://tede.mackenzie.br/jspui/handle/tede/2748.
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Previous issue date: 2011-08-05Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
The technology environment in the broadcast area using analog technology was defined and did not offer a great research interest, in specific topics related to development of the transmitting antenna for broadcast television. With the implementation of the transmission system employing digital technology, which adds as main news the possibility of mobility and portability of the receiving system, the interest in studies and researches returned, showing one of the main themes to be developed using circular polarization or elliptical compared with horizontal polarization, that was most used by broadcasters. Given this new scenario and the need for evaluation by a scientific methodology of the radiating system in the transmission station performance, goals were established that define the scope for this research: to analyze the influence of the radiating system depending on the desired coverage area and the reception possibilities internal fixed , external fixed, portable and mobile, considering the diversity specific propagation environment of the region studied due to topographical and environmental condition. The criteria to be used will be the theoretical propagation prediction and field survey of the signals received which will provide data for the analysis of variables that influence the behavior of the transmission system, considering the location and technical characteristics of the main transmission station installation and different polarization of the radiating system configurations in horizontal, vertical and elliptical.
O cenário tecnológico na área de transmissão empregando tecnologia analógica estava bem segmentado e não oferecia um ambiente de grande interesse em pesquisas específicas para desenvolvimentos de temas relacionados a antena de transmissão para televisão aberta. Com a implantação do sistema de transmissão empregando a tecnologia digital, que agrega como principal novidade a possibilidade de mobilidade e portabilidade do sistema de recepção , o interesse nos estudos e pesquisas retomou, apresentando como um dos principais temas a serem desenvolvidos a utilização de polarização circular ou elíptica comparada com a polarização horizontal, que era a mais utilizada pela emissoras. Tendo em vista este novo cenário e a necessidade de avaliação por meio de uma metodologia científica do comportamento do sistema irradiante de transmissão no resultado no desempenho da estação transmissora, foram estabelecidas as metas que definem o escopo para este trabalho: analisar a influência do tipo de sistema irradiante em função da área de cobertura desejada e das possibilidades de recepção fixa interna, fixa externa, portátil e móvel, frente às diversidades específicas do ambiente de propagação da região estudada devido às condições topográficas e ambientais. Os critérios a serem empregados serão os teóricos de predição de propagação e prático de levantamento de campo dos sinais recebidos os quais irão fornecer dados para a análise das variáveis que influenciam no comportamento do sistema de transmissão, considerando o local e as características técnicas de instalação da estação de transmissão principal e variando a polarização do sistema irradiante nas configurações horizontal, vertical e elíptica.
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Chiu, Cheng-Wei, and 邱振瑋. "A Study on Antennas and Wave Propagation for Packaging RFID." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/06174501738167458200.
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碩士國立臺灣科技大學
電機工程系
93
This thesis studies the antenna and wave propagation properties of the radio frequency identification (RFID) for packaging objects. A finite difference time domain software package XFDTD and a finite element software package HFSS are applied in this study. Particularly, a tag antenna for Alien RFID IC is designed and some parameters to control the properties of the tag antenna are evaluated. Also, measurements of the properties and the readable distance of the tag antenna are performed in NTUST Antenna Far-field Anechoic Chamber to verify the performance of the tag antenna design. On the other hand, contains in packages will influence tag antenna and wave propagation properties significantly. Although different antenna designs may be employed for specific applications, wave propagation through stacked packages is usually a difficult problem. Thus, the efficiency of the packaging RFID system may be affected. To solve this problem, a practical method for the antenna design and wave propagation in stacked packages has been studied. Patent applications are submitted for the results developed in this study.
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Chun, Chen Yen, and 陳彥君. "Broadband Antennas Design and Applications - Propagation Property with Various Mediums." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/11811079450004683975.
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碩士大葉大學
電信工程學系碩士班
94
For recognizing the EM characteristics of mediums, the simulation is developed in this thesis. Using the simulated results of S parameters, the dielectric constant and loss tangent of medium can be calculated by EM formulas. Generally, the transmitting antennas in test ranges are consist of various narrow band antennas for wide band applications. The drawback are higher cost for purchasing the probe antennas, time consuming for changing and uncertainty of the antenna patterns; therefore, a novel transmitter antenna constructed with low directivity wideband horn and wideband balun will be developed in this thesis and applied for the Near-field antenna measurement system. The operating frequency from 1 GHz to 18 GHz, low directivity and symmetry antenna pattern are achieved. Meanwhile, a ultra-wideband bow-tie receiving antenna is designed and applied in the water from 3GHz to 12.5 GHz. Both S-parameters and radiation patterns are measured by the network analyzer and impulse time domain antenna measurement system respectively. The EM wave propagation for various media is analyzed
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Jiang, Hong Sheng, and 江宏昇. "Simulation and measurement for indoor propagation using diversity monopole antennas." Thesis, 1995. http://ndltd.ncl.edu.tw/handle/40644828691505988502.
Full text
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Merola, Christopher S. "Resonant Antennas Based on Coupled Transmission-Line Metamaterials." 2011. https://scholarworks.umass.edu/theses/629.
Full textAbstract:
A novel microstrip patch antenna topology is presented for achieving a dual-band response with arbitrarily closely spaced resonances. This topology is based on a coupled transmission line structure in order to take advantage of the separation in propagation constants for parallel (even-mode) and anti-parallel (odd-mode) current modes. Applying a metamaterials inspired design approach, periodic reactive loadings are used to design the underlying transmission line to have specific propagation constants necessary to realize a desired separation between two resonant frequencies. Using a single probe feed for a finite coupled line segment, both even-and odd-mode resonances can be excited to radiate efficiently at their respective design frequencies. The efficiency of the odd-mode radiation is enhanced by separating the two lines, while strong coupling is maintained by inserting a series of narrowly-separated thin loops between them. Several example resonant antenna designs, in the 2.45 GHz band, are presented.
The directivities of these microstrip patch antennas are enhanced by optimizing the physical length of the resonant structure. For a resonant antenna obtained by cascading several unit cells of reactively loaded microstrip segments, dispersion analysis is employed for the unit-cell design. Maximum directivity is achieved by choosing the overall physical length to be slightly less than a half wavelength in free space at the design frequency. This gain optimization is applied to three coupled-line antennas, as well as a single resonance patch. Excellent agreement is observed between simulated and measured responses across all designs.
The potential of loading the coupled line structure with active components is also explored. Varactor diodes are placed on coupled-line structures in two configurations. In one configuration, both resonant frequencies are affected. In the other configuration, only the odd-mode characteristics are reconfigured. In this way, the resonant frequency of either one or both modes can be adjusted by applying a DC bias voltage to the varactor diode loading elements. Two antennas, one employing each of these topologies, were designed and fabricated. Control of the resonant frequency over the predicted range through applying a bias voltage is observed with the fabricated prototypes.
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Gutierrez, Felix active 2013. "Millimeter-wave and sub-terahertz on-chip antennas, arrays, propagation, and radiation pattern measurements." 2013. http://hdl.handle.net/2152/23109.
Full textAbstract:
This dissertation focuses on the development of next generation wireless
communications at millimeter-wave and sub-terahertz frequencies. As wireless
providers experience a bandwidth shortage and cellular subscribers demand
faster data rates and more reliable service, a push towards unused carriers fre-
quencies such as 28 GHz, 60 GHz, and 180 GHz will alleviate network conges-
tion while simultaneously providing massive bandwidths to consumers. This
dissertation summarizes research in understanding millimeter-wave wireless
propagation, the design and fabrication of millimeter-wave and sub-terahertz
on-chip antenna arrays on an integrated circuit semiconductor process, and
the accurate measurement of on-chip antenna radiation patterns in a wafer
probe station environment.text
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Hailu, Daniel. "Hybrid Spectral Ray Tracing Method for Multi-scale Millimeter-wave and Photonic Propagation Problems." Thesis, 2011. http://hdl.handle.net/10012/6355.
Full textAbstract:
This thesis presents an efficient self-consistent Hybrid Spectral Ray Tracing (HSRT) technique for analysis and design of multi-scale sub-millimeter wave problems, where sub-wavelength features are modeled using rigorous methods, and complex structures with dimensions in the order of tens or even hundreds of wavelengths are modeled by asymptotic methods.
Quasi-optical devices are used in imaging arrays for sub-millimeter and terahertz applications, THz time-domain spectroscopy (THz-TDS), high-speed wireless communications, and space applications to couple terahertz radiation from space to a hot electron bolometer. These devices and structures, as physically small they have become, are very large in terms of the wavelength of the driving quasi-optical sources and may have dimension in the tens or even hundreds of wavelengths. Simulation and design optimization of these devices and structures is an extremely challenging electromagnetic problem. The analysis of complex electrically large unbounded wave structures using rigorous methods such as method of moments (MoM), finite element method (FEM), and finite difference time domain (FDTD) method can become almost impossible due to the need for large computational resources. Asymptotic high-frequency techniques are used for analysis of electrically large quasi-optical systems and hybrid methods for solving multi-scale problems.
Spectral Ray Tracing (SRT) has a number of unique advantages as a candidate for hybridization. The SRT method has the advantages of Spectral Theory of Diffraction (STD). STD can model reflection, refraction and diffraction of an arbitrary wave incident on the complex structure, which is not the case for diffraction theories such as Geometrical Theory of Diffraction (GTD), Uniform theory of Diffraction (UTD) and Uniform Asymptotic Theory (UAT). By including complex rays, SRT can effectively analyze both near-fields and far-fields accurately with minimal approximations. In this thesis, a novel matrix representation of SRT is presented that uses only one spectral integration per observation point and applied to modeling a hemispherical and hyper-hemispherical lens. The hybridization of SRT with commercially available FEM and MoM software is proposed in this work to solve the complexity of multi-scale analysis. This yields a computationally efficient self-consistent HSRT algorithm. Various arrangements of the Hybrid SRT method such as FEM-SRT, and MoM-SRT, are investigated and validated through comparison of radiation patterns with Ansoft HFSS for the FEM method, FEKO for MoM, Multi-level Fast Multipole Method (MLFMM) and physical optics. For that a bow-tie terahertz antenna backed by hyper-hemispherical silicon lens, an on-chip planar dipole fabricated in SiGe:C BiCMOS technology and attached to a hyper-hemispherical silicon lens and a double-slot antenna backed by silica lens will be used as sample structures to be analyzed using the HSRT. Computational performance (memory requirement, CPU/GPU time) of developed algorithm is compared to other methods in commercially available software. It is shown that the MoM-SRT, in its present implementation, is more accurate than MoM-PO but comparable in speed. However, as shown in this thesis, MoM-SRT can take advantage of parallel processing and GPU. The HSRT algorithm is applied to simulation of on-chip dipole antenna backed by Silicon lens and integrated with a 180-GHz VCO and radiation pattern compared with measurements. The radiation pattern is measured in a quasi-optical configuration using a power detector. In addition, it is shown that the matrix formulation of SRT and HSRT are promising approaches for solving complex electrically large problems with high accuracy.
This thesis also expounds on new measurement setup specifically developed for measuring integrated antennas, radiation pattern and gain of the embedded on-chip antenna in the mmW/ terahertz range. In this method, the radiation pattern is first measured in a quasi-optical configuration using a power detector. Subsequently, the radiated power is estimated form the integration over the radiation pattern. Finally, the antenna gain is obtained from the measurement of a two-antenna system.
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Zuniga, Barahona Christian David. "Channel modeling of an antenna plasma-plume system." Thesis, 2005. http://hdl.handle.net/2152/2382.
Full text
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Wong, Alex H. C. "Antenna Selection and Deployment Strategies for Indoor Wireless Communication Systems." 2007. http://hdl.handle.net/2292/432.
Full textAbstract:
Effective antenna selection and deployment strategies are important for reducing co-channel interference in indoor wireless systems. Low-cost solutions are essential, and strategies that utilise simple antennas (such as directional patches) are advantageous from this perspective. However, performance is always an issue and the improvements achievable through clever antenna deployment need to be quantified. In this thesis, an experimental investigation of indoor propagation comparing the performance of directional antennas and multiple-element arrays (MEAs) with omni-directional antennas is reported. Estimation of the performance of a direct sequence code division multiple access (DS-CDMA) system operating in a variety of deployment scenarios allows the identification of a range of performance-limiting factors and the optimal deployment strategies. It is shown that the orientation of single-element directional antennas can significantly impact on system performance compared to omni-directional antennas in traditional systems. The deployment of MEAs with an active diversity combining scheme can further improve system performance by more than one order of magnitude. From the perspective of system planning, the choice of antenna selection and deployment options depends on the current and future demand for system performance and the financial resources available. An evolutionary path has been proposed to provide a smooth transition from conventional (low-cost) to high-performance (high-cost) antenna systems as demand dictates. Other performance-limiting factors in indoor wireless systems include the physical environment and external interference. It is also shown that electromagnetically-opaque obstacles in the environment can amplify the effectiveness of the antenna deployment by acting as physical zone boundaries that restrict interference. External interference has been shown to cause a significant degradation to the performance of an indoor system when the carrier-to-external-interference ratio (CEIR) is below 30 dB. This performance degradation can be minimised by appropriate antenna deployment, although the optimum antenna orientations depends on the strength of the external interference.
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(7478276), Vladlen Alexandrovich Podolsky. "INVESTIGATION OF PLASMAS SUSTAINED BY HIGH REPETITION RATE SHORT PULSES WITH APPLICATIONS TO LOW NOISE PLASMA ANTENNAS." Thesis, 2019.
Find full textAbstract:
In the past two decades, great interest in weakly ionized plasmas sustained by high voltage nanosecond pulsed plasmas at high repetition rates has emerged. For such plasmas, the electron number density does not significantly decay between pulses, unlike the electron temperature. Such conditions are favorable to reconfigurable plasma antennas where the low electron temperature may enable the reduction of the Johnson–Nyquist thermal noise if an antenna is operated in the plasma afterglow. Moreover, it may be possible to sustain such conditions with RF pulses. Doing so could enable a plasma antenna that transmits the driving frequency when the pulse is applied and receives other frequencies with low thermal noise between pulses.
To study nanosecond pulsed plasmas, experiments were performed in a parallel-plate electrode configuration in argon and nitrogen gas at a pressure of several Torr and repetition frequencies of 30-75 kHz. To measure the time-resolved electron number density in the afterglow of each pulse, a custom 58.1 GHz homodyne microwave interferometer was constructed. The voltage and current measurements were made using a back current shunt (BCS). Initial analysis of the measured electron density in both plasmas indicated that the electron thermalization was much faster than the electron decay. In the nitrogen plasma, dissociative recombination with cluster ions was the dominant electron loss mechanism. However, the dissociative recombination rates of the electrons in the argon plasma suggested the presence of molecular impurities, such as water vapor. Therefore, to better understand the recombination mechanisms in argon plasma with trace amounts (0.1% or less by volume) of water vapor under the experimental conditions, a 0-D kinetic model was developed and fit to the experimental data. The influence of trace amounts of water on the electron temperature and density decay was studied by solving electron energy and continuity equations. It was found that in pure argon, Ar+ ions dominate while the electrons are very slow to thermalize and recombine. Including trace amounts of water impurities drastically reduces the time for electrons to thermalize and increases their rate of recombination.
In addition to large quasi-steady electron number densities and low electron temperature in the plasma afterglow, plasmas sustained by nanosecond pulses use a lower power budget than those sustained by RF or DC supplies. The efficiency of the power budget can be characterized by measuring the ionization cost per electron, defined as the ratio of the energy deposited in a pulse to the total number of electrons created. This was experimentally determined in air and argon plasmas at 2-10 Torr sustained by 1-7 kV nanosecond pulses at repetition frequencies of 0.1-30 kHz. The number of electrons were determined from the measured electron density through microwave interferometry and assuming a plasma volume equivalent to the volume between electrodes. The energy deposited was calculated from voltage and current measurements using both a BCS as well as high frequency resistive voltage divider and fast current transformer (FCT). It was found that the ionization cost in all conditions was within a factor of three of Stoletov’s point (the theoretical minimum ionization cost) and two orders of magnitude less than RF plasma.
Having shown that it is possible to
generate high electron density, low electron temperature plasmas with
nanosecond pulses, it was necessary to now create a plasma antenna prototype.
Initially, commercial fluorescent light bulbs were used and ignited using
surface wave excitation at various RF frequencies and powers. The S11
of the antenna response was measured by a VNA through a novel coupling circuit,
while the deposited power was measured using a bi-directional coupler. Next, a
custom plasma antenna was created in which the pressure and gas composition
could be varied. In addition to the S11 and deposited power, the
antenna gain, and the electron number density were also measured for a pure
argon plasma antenna at pressures of 0.3-1 Torr. Varying the applied power shifts
the antenna resonance frequency while increasing the excitation frequency
caused an increase in measured electron density for the same deposited power.
Initial tests using direct electrode excitation of a twin-tube integrated
compact fluorescent light bulb with nanosecond pulses have successfully been
achieved. Future efforts include designing the proper circuitry to time-gate
out the large pulse voltage to facilitate safe antenna measurements in the
plasma afterglow.
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Hussain, Intikhab. "Channel modelling and analysis of Wits mock-mine with different antenna parameters." Thesis, 2017. http://hdl.handle.net/10539/23519.
Full textAbstract:
A research report submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in partial fulfilment of the requirements for the degree of Master of Science in Engineering, 2017In the mining industry, communications systems are important for ensuring personnel safety and optimizing the mining processes underground. Achieving robust and reliable through-the-air (TTA) communication systems has always been a challenge in the underground mining environment due to harsh and dynamic conditions. TTA requires radio channel characterization for efficient designing and deploying of the communications systems. The literature covers the statistical radio propagation of a room and pillar coal mine, a longwall coal mine, CANMET Gold mine, Camborne School of Mines hard rock mine tunnel, MUZ Coal mine, an iron-ore mine and a lead-zinc mine with linearly polarized antennas at different frequencies. [Abbreviated Abstract. Open document to view full version]
MT 2017