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1
Chen, Cheng. „Simultaneous transmission of baseband signal and in band RF signal“. Thesis, University of Cambridge, 2015. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.708805.
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2
Cui, Xian. „Efficient radio frequency power amplifiers for wireless communications“. Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1195652135.
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Barč, Andrej. „Přenos radiofrekvenčního signálu optickým vláknem“. Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2021. http://www.nusl.cz/ntk/nusl-442409.
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This work deals with the transmission of optical radiation modulated by a radio frequency signal through an optical fiber. Furthermore, it describes the principles of communication and area coverage. It points out the practical use of components located in the communication chain of this system. Explains the functionality of the properties and the division of individual components. It introduces the benefits and limitations of this system. It further describes the creation of a topology suitable for laboratory measurement of RoF technology. Provides experimental measurement of C-band parameters. Indicates the possible use of RoF technology using a wireless optical link. A part of the work is also a sample laboratory protocol.
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Zhao, Chunming. „Distortion-based crest factor reduction algorithms in multi-carrier transmission systems“. Diss., Atlanta, Ga. : Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/26525.
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Thesis (Ph.D)--Electrical and Computer Engineering, Georgia Institute of Technology, 2008.Committee Chair: Zhou, G. Tong; Committee Member: Kenney, J. Stevenson; Committee Member: Li, Ye (Geoffrey); Committee Member: Ma, Xiaoli; Committee Member: Yuan, Ming. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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Ameziane, El Hassani Chama. „Contribution à la réalisation d’un oscillateur push-push 80GHz synchronisé par un signal subharmonique pour des applications radars anticollisions“. Thesis, Bordeaux 1, 2010. http://www.theses.fr/2010BOR14025/document.
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Ce travail de thèse s’inscrit dans le cadre d’un projet Français « VéLo » qui est une collaboration entre l’industriel STMicroelectronics et plusieurs laboratoires dont les laboratoires IMS-bordeaux et LAAS. Le but du projet est de concevoir un prototype de radar anticollision millimétrique. Dans ce travail un synthétiseur de fréquence est implémenté. Ce dernier sera intégré dans la chaine de réception du démonstrateur. Une étude bibliographique des architectures classiques de système de radiocommunication a été réalisée. Des exemples d’architectures rencontrées dans le domaine millimétrique ont été étudiés.L’objet principal de cette thèse est l’étude des oscillateurs synchronisés par injection ILO. L’objectif est de réaliser un oscillateur verrouillé par injection qui sera piloté par un oscillateur de fréquence plus basse possédant des caractéristiques de stabilité et de bruit meilleures.Dans ce travail de thèse, le mécanisme de verrouillage des oscillateurs par injection a été décrit. Un modèle de synchronisation par injection série, basé sur la théorie de Huntoon Weiss et inspiré du travail de Badets réalisé sur les oscillateurs synchrones verrouillés par injection parallèle, est proposé. La théorie établie a permis d’exprimer la plage de synchronisation en fonction de la topologie utilisée et des composants de la structure. La validité de la théorie a été évaluée par la simulation de la structure. Les résultats présentés montrent une bonne concordance entre la simulation et la théorie et permettent de valider le principe de synchronisation par injection. La faisabilité de l’intégration d’un ILO millimétrique synchronisé par l’harmonique d’un signal de référence de fréquence plus basse a été démontrée expérimentalement. Le synthétiseur de fréquence est réalisé en technologie BiCMOS 130nm pour des applications millimétriques de STMicroelectronics. Ce dernier opère dans une plage de 2GHz autour de la fréquence 82,5GHz. Les performances en bruit du synthétiseur sont satisfaisantes. Le bruit de phase de l’ILO recopie celui du signal injecté. Les équipements de mesures utilisés, le bruit de phase de l’oscillateur atteint des valeurs inférieures à -110dBc/Hz à 1MHz de la porteuseThis thesis is a part of a French project "VELO". The project is collaboration between STMicroelectronics and several laboratories including IMS-Bordeaux and LAAS laboratories. The aim of this project is to achieve a prototype of millimeter anti-collision radar. In this work a frequency synthesizer is implemented. This circuit will be incorporated in the reception chain of the demonstrator. A bibliographical study of classical architecture was completed. Examples of architectures encountered in the millimeter frequency range have been studied. The purpose of this thesis is to study the phenomena of synchronization in oscillators. The objective is to design an injection locked oscillator ILO driven by another oscillator, the second oscillator operates at lower frequency and offers better stability and noise characteristics.In this thesis, the injection locking mechanism of the oscillators has been described. A model of synchronization by series injection is proposed. The model is based on the theory of Huntoon and Weiss and inspired by Badets’ work performed on parallel injection. The theory expresses the synchronized frequency range depending on the used topology and the values of the components. The validity of the theory was evaluated by simulation. The results show good agreement between simulation and theory and validate the principle of synchronization by injection.The feasibility of a millimeter ILO synchronized by the harmonic of a reference signal operating at lower frequency has been demonstrated experimentally. The synthesizer was implemented in BiCMOS technology for 130nm applications millimeter of STMicroelectronics. The oscillator operates at 82.5 GHz and performs a frequency range of 2GHz. The noise performance of the synthesizer is satisfactory. The phase noise of the ILO depends on the reference phase noise, and reaches values of -110dBc/Hz at 1MHz from the carrier frequency
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Matarrese, Vincent D. „Tapered radio frequency transmission lines“. PDXScholar, 1992. https://pdxscholar.library.pdx.edu/open_access_etds/4329.
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A transformation used to obtain solutions for the beam parameter equation of fiber optics is applied to the second order differential equation for nonuniform transmission lines. Methods are developed for deriving possible transmission line tapers from known solutions of the transformed equation. This study begins with a comprehensive overview of previous work done to obtain closed-form solutions for the transmission line equations. Limitations of the lumped parameter model are also discussed. As part of this thesis, a tapered transmission line is constructed, based on one of the solutions obtained from the fiber optics studies. A discussion of the design and measurement results are given in the final chapter.
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Barton, Taylor Wallis. „Phase manipulation for efficient radio frequency transmission“. Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/78474.
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Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2012.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 109-112).
Power amplifiers (PAs) for microwave communications are generally the most power-hungry element of a transmitter. High linearity is required for modern digital communications standards, and often is achieved at the expense of efficiency. Outphasing architectures, which combine multiple nonlinear but efficient switching PAs into a system with an overall linear response, represent a promising strategy for breaking the efficiency/linearity tradeoff inherent to conventional PAs. This work explores methods for efficient PA design using outphasing techniques. Two aspects of outphasing design are considered. First, a wide-band phase modulator is introduced that uses a single current-steering digital to analog converter (DAC) structure and discrete clock prerotation. This topology takes advantage of specifications particular to outphasing architectures to reduce matching requirements as compared to a two-DAC phase modulator while providing wideband capability. The phase modulator is demonstrated in 65-nm CMOS, operates over a carrier frequency range of 1.2-4.2 GHz and has a 12-bit phase resolution and sample rate of 160 MSamples/second. The second technique is a novel four-way lossless power combiner and outphasing system which provides ideally lossless power combining along with resistive loading of switching power amplifiers over a wide output range. This work presents the first-ever demonstration of this system at microwave frequencies. Particular attention is paid to the microwave-specific aspects of implementation. A 60-W GaN prototype demonstrates the outphasing and dynamic performance, which closely matches the expected performance despite the challenges of operating at microwave frequencies.
by Taylor Wallis Barton.
Sc.D.
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Mazal, Mohammed Jellop. „Optically scanned radio frequency field imaging“. Thesis, King's College London (University of London), 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.266654.
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Aubert, Louis-Marie. „Mise en place d'une couche physique pour les futurs systèmes de radiocommunications hauts débits UWB“. Phd thesis, Rennes, INSA, 2005. https://tel.archives-ouvertes.fr/tel-00011745.
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L'UWB (Ultra Wide Band) consiste à transmettre des signaux entre 3. 1 et 10. 6 GHz avec une puissance limitée à -41. 3 dBm/MHz. Pour les communications hauts débits (100 à 500 Mbit/s) et courtes portées (1 à 10 m), les solutions de l'état de l'art reposent sur des traitements numériques complexes. Mitsubishi ITE propose une solution alternative multi-bandes (MB) impulsionnelle basée sur un récepteur non-cohérent. La démodulation OOK est effectuée par une détection d'énergie originale avec un seuillage adapté dynamiquement suivant les conditions de propagation. La parallélisation complète de ce système MB-OOK permet à la fois d'éviter les interférences inter-symboles et de récupérer la quasi totalité de l'énergie disponible. En outre, l'approche impulsionnelle limite les évanouissements du signal sur canal multi-trajets. La comparaison des systèmes MB-OOK et MB-OFDM démontre la pertinence de la solution proposée pour des applications très hauts débits, courte portée et faible consommationThe UWB (Ultra Wide Band) consists in transmitting signal between 3. 1 and 10. 6 GHz with a power limited to –41. 3 dBm/MHz. For high data rate (100 to 500 Mbit/s) and short range (1 to 10 m) applications, the state of the art solutions are based on complex digital processing. Mitsubishi ITE proposes an alternative multiband (MB) impulse radio solution based on a non-coherent receiver. The OOK demodulation is done by an original energy detection with a threshold which is adapted dynamically according to propagation conditions. The complete parallelization of this MB-OOK solution allows the system to both avoid inter-symbol interference and recover virtually all available energy. Furthermore the impulsive approach limits multipath channel fading. The comparison of MB-OOK and MB-OFDM systems demonstrates the pertinence of the proposed solution for high data rates and short range applications with low power consumption
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Nader, Charles. „Enhancing Radio Frequency System Performance by Digital Signal Processing“. Licentiate thesis, University of Gävle, Department of Electronics, Mathematics and Natural Sciences, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:hig:diva-7312.
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In this thesis measurement systems for the purpose of characterization of radio frequency power amplifiers are studied. Methods to increase the speed, accuracy, bandwidth, as well as to reduce the sampling requirements and testing cost are presented. A method intended for signal shaping with respect to peak to-average ratio reduction and its effects-improvements on the radio frequency front-end performance is investigated.
A time domain measurement system intended for fast and accurate measurements and characterization of radio frequency power amplifiers is discussed. An automated, fast and accurate technique for power and frequency sweep measurements is presented. Multidimensional representation of measured figure of merits is evaluated for its importance on the production-testing phase of power amplifiers.
A technique to extend the digital bandwidth of a measurement system is discussed. It is based on the Zhu-Frank generalized sampling theorem which decreases the requirements on the sampling rate of the measurement system. Its application for power amplifiers behavioral modeling is discussed and evaluated experimentally.
A general method for designing multitone for the purpose of out-of-band characterization of nonlinear radio frequency modules using harmonic sampling is presented. It has an application with the validation of power amplifiers behavioral models in their out-of-band frequency spectral support when extracted from undersampled data.
A method for unfolding the frequency spectrum of undersampled wideband signals is presented. It is of high relevance to state-of-the-art radio frequency measurement systems which capture repetitive waveform based on a sampling rate that violates the Nyquist constraint. The method is presented in a compact form, it eliminates ambiguities caused by folded frequency spectra standing outside the Nyquist band, and is relevant for calibration matters.
A convex optimization reduction-based method of peaks-to-average ratio of orthogonal frequency division multiplexing signals is presented and experimentally validated for a wireless local area network system. Improvements on the radio frequency power amplifier level are investigated with respect to power added efficiency, output power, in-band and out-of-band errors. The influence of the power distribution in the excitation signal on power amplifier performance was evaluated.
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Jereb, Alexander Robert. „Design and implementation of a Radio-Frequency detection algorithm for use within A Radio-Frequency System on Chip“. University of Dayton / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1608145466947488.
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Kloos, Gerold. „Radio-Frequency Signal Strength Based Localisation in Unstructured Outdoor Environments“. Faculty of Engineering and Information Technologies, 2008. http://hdl.handle.net/2123/2242.
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Doctor of Philosophy (PhD)This thesis addresses the issues arising in range-only localisation and tracking using Radio Frequency Received Signal Strength Indicator measurements. One of the key issues in Radio Frequency (RF) based localisation and tracking applications is to obtain an accurate sensor representation. Such a sensor model is one of the prerequisites to achieve high accuracy and precision in the localisation and tracking task. The sensor models used at present for this task are very simplistic, and as a consequence are unable to achieve highly accurate and precise localisation. While such an accurate sensor description is desirable it has not been presented for RF sensors. This thesis addresses the task of obtaining an accurate sensor model for RF sensors. The major drawbacks of the most commonly used model, the nth power model, are demonstrated. A new model to satisfy the necessary requirements for high accuracy localisation is developed. This model is based on theoretical considerations and experimental data. It depicts the real occurring behaviour of RF sensors more closely than the models used so far for RF based range-only localisation. The use of this better sensor representation offers the possibility of achieving more accurate localisation. The expected performance of the alternative sensor model is compared to the commonly used nth power model. Furthermore, the inherent properties of the new sensor model are presented and their ramifications with regards to the goal of achieving highly accurate localisation are discussed. In addition to the sensor model development, the well-known probabilistic filtering techniques Kalman Filter, Particle Filter and Histogram Filter are compared and used to implement 1-dimensional and 2-dimensional range-only trackers. The filtering techniques are evaluated with respect to their suitability for appropriately handling the new multi-modal sensor model and the resulting multi-modal state distributions, and to provide correct and conclusive localisation and tracking results. Results from experiments using real data obtained in outdoor environments with a prototype RF localisation system as well as results obtained from simulations are presented in this thesis to validate the theoretical findings and the newly developed sensor model.
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Assimakopoulos, Philippos. „Nonlinear effects in OFDM signal transmission over radio over fibre links“. Thesis, University of Kent, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.633700.
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The dynamic range limitations that arise from nonlinearity in low-cost and low complexity directly modulated radio over fibre (RoF) links are examined. Statistical non linear models are presented and applied to the case of a RoF link with a low biased laser diode. The effects of distortion on the Error Vector Magnitude (EVM) performance of Orthogonal Frequency-Division Multiplexing (OFDM) signals with different numbers of subcarriers and the connection to the Peak-ta-Average Power Ratio (PAPR) of the signals are investigated. Statistical distributions of the EVM over a large number of transmitted OFDM frames are gained from experimental measurements and analyses of idealized processes. The measurement results show that as the number of subcarriers is reduced the distribution means are not dependent in the expected way on the statistical PAPR of the transmitted OFDM signals. Instead, it is shown that in regions of moderate distortion the median of the EVM is more closely related to the statistical PAPR and to the required back-off for signals with different numbers of subcarriers. Through the employed statistical analysis, the asymptotic convergence of the EVM result to that expected in the idealized case is observed. The results of this analysis also show, how, including the EVM variance in estimations for back-off might be useful, how, in a measurement, the number of transmitted OFDM frames affects the estimated mean EVM. Differing EVM results for subcarriers at the edge and middle of the signal band show that distortion affects the subcarriers at the middle of the band to a stronger degree and that their behaviour is correlated "to the statistical PAPR of the individual signals. Then, a laser model validated against measured performance is designed arid used for simulating the performance of a subcarrier multiplexed 4th generation mobile/wireless RoF transmission system. Predictions indicate that the architecture provides adequate performance in terms of EVM, for different IFFT sizes and modulation levels of up to 256 QAM (at leastL and a combined raw data rate of up to 3.2 Gbps. Based on a 1.5% EVM transmitter requirement with 256 QAM, a system dynamic range of approximately 5.1 dB is predicted. Finally, the use of companding in a directly modulated RaF link, with the aim of reducing the amplification (and isolation) requirements in the remote antenna unit, is demonstrated, quantified through EVM measurements. The resulting improvements in output power are approximately 4.7 dB at an EVM transmitter requirement of 5.6 %, while in terms of the point of onset of distortion-induced EVM increase, the improvement is approximately 7.6 dB.
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Apostolou, Nikolaos. „Signal synthesis with dynamically-changed power spectral density in a software defined radio transmitter“. Thesis, Monterey, California. Naval Postgraduate School, 2003. http://hdl.handle.net/10945/874.
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Approved for public release; distribution is unlimitedThe objective of this thesis is to synthesize signals with a dynamically change power spectral density, in a SDR transmitter, utilizing the most appropriate channels, modulation schemes and transmission rates for communication, based on the noise profile (AWGN plus interferences) of the link, in order to achieve performance within some predefined acceptable levels. The objective is obtained by simulation.
Major, Hellenic Army
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Krasňanský, Milan. „Radar Signal Processing for Radio Altimeter“. Master's thesis, Vysoké učení technické v Brně. Fakulta informačních technologií, 2017. http://www.nusl.cz/ntk/nusl-363816.
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Táto diplomová práca sa zaoberá návrhom a implementáciou algoritmu pre spracovaniu signálu z radaru využívajúceho frekvenčne modulovanú kontinuálnu vlnu. Cieľom je implementácia algoritmu, ktorý by bol dostatočne rýchly (výpočet v reálnom čase na cieľovej platforme) a dostatočne presný pre použitie v rádiovýškomere v ľahkom lietadle so zameraním na použitie počas pristávacieho manévru. Hlavnou metódou spracovania signálu, použitou v implementácii, je Diskrétna Fourierova transformácia. Vytvorený algoritmus bol otestovaný na reálnych letových dátach a pre pristávací manéver dosiahol uspokojivé výsledky.
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Johnstone, G. G. „An investigation into filters utilising coupled transmission lines“. Thesis, University of Surrey, 1995. http://epubs.surrey.ac.uk/844257/.
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This thesis addresses itself to the solution of a number of problems which arise in the development of Radio Frequency filters, particularly those involving coupled transmission lines as resonant elements. The text is divided into a number of sections dealing with individual topics. After a brief description of Darlington filter design principles, there is an account of the pivotal role of quarter wave sections and their vital part in the realisation of high frequency filters. This is followed by the development of new material relating to equivalent circuits of physical lines in terms of quarter wave sections, and its application to improvements in the design of wide-band filters. There follows an account of a new procedure for calculating the dimensions of comb-line and inter-digital filters. This section includes a new proposal for the inversion of Getsinger's procedure to permit the calculation of rectangular rod dimensions and spacings from given electrical data. There is also an algorithm for use with round rods which circumvents the tedious manual interpolation procedure devised by Cristal. There follows an investigation of and a proposed solution to a long-known but unexplained discrepancy existing between the calculated and measured pass-band width of the class of comb-line filters. With the new procedure the discrepancy reported previously to be of the order of 10% is eliminated. Finally, experimental evidence is adduced to verify the algorithms outlined in the preceding chapters.
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Griffin, Joshua David. „A Radio Assay for the Study of Radio Frequency Tag Antenna Performance“. Thesis, Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/7112.
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In recent years, passive radio frequency (RF) tags that
communicate using modulated backscatter radiation have shown great
potential for use in inventory management, parcel and postal
tracking, for use as remote sensors, and in a host of other Radio
Frequency Identification (RFID) applications. However, for the
widespread use of these tags to become reality, much basic
research is needed to reduce the cost, increase the range, and
increase the reliability of the RF tag. This research seeks to
enhance the performance of passive RF tags by developing a series
of tests, or radio assay, to measure the following: the
performance of RF tag antennas as a function of antenna material
and manufacturing technique and the antenna performance when
attached to various materials. The radio assay experiments are
designed for RF tag antennas that operate in the far field of the
tag reader and communicate using modulated backscatter radiation
at 915 MHz. Three flexible, folded dipoles, printed on plastic
substrates, were measured in the radio assay experiments. The
results of the experiments include the following: the antenna gain
penalty (relative to a baseline antenna) for each antenna material
and manufacturing technique, the antenna gain penalty (relative to
the free space antenna gain) due to material losses when the tag
antenna is attached to an object, and the benefits (in terms of
antenna gain) of tuning each tag antenna to the material to which
it is attached. The results are presented in a form to aid RF
engineers in the design of RF tag system link budgets.
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Björsell, Niclas. „Modeling Analog to Digital Converters at Radio Frequency“. Doctoral thesis, KTH, Signalbehandling, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4523.
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Det här arbetet handlar om att ta fram beteendemodeller av analog till digital omvandlare avsedda för tillämpningar i radiofrekvensområdet. Det gäller tillämpningar inom telekommunikation men även in test- och mätinstrument där omvandlingen från analoga till digitala signaler ofta är en prestandamässig flaskhals. Modellerna är avsedda att användas för att efterbehandla utdata från omvandlaren och på så sätt förbättra prestanda på den digitala signalen. Genom att skapa modeller av verkliga omvandlare och hur dessa avviker från ett idealt beteende kan ofullständigheter korrigeras genom så kallad postkorrigering. Beteendemodeller innebär att genererar en lämplig insignal, mäta utdata och beräkna en modell. För omvandlare i radiofrekvensområdet ställs höga krav på instrumentering. Den testutrustningen som används är baserad på moderna högprestanda instrument som har kompletterats med specialbyggd utrustning för signalkonditionering och datainsamling. I avhandlingen har även olika insignaler utvärderats med såväl teoretisk som experimentell analys. Det finns ett flertal olika varianter av modeller för att modulera ett olinjär, dynamisk system. För att få en parametereffektiv modell har utgångspunkten varit att utgå från en Volterramodell som på ett optimalt sätt beskriver svagt olinjära dynamiska system, så som analog till digital omvandlare, men som är alltför omfattande i antal parametrar. Volterramodellens har sedan reducerats till en mindre parameterintensiv, modellerstruktur på så sätt att Volterrakärnans symmetriegenskaper jämförts med symmetrierna hos andra modeller. En alternativ metod är att använda en Kautz-Volterramodell. Den har samma generella egenskaper som Volterramodellen, men är inte lika parameterkrävande. I den här avhandlingen redovisas experimentella resultat av Kautz-Volterramodellen som i framtiden kommer att vara intressanta att använda för postkorrigeringen. För att kunna beskriva beteenden som en dynamiska olinjära modellen inte klarar av har modellen kompletterats med en statisk styckvis linjär modellkomponent. I avhandlingen presenteras en sluten lösning för att identifiera samtliga paramervärden i modellen. Vidare har det i avhandlingen genomförs en analys av hur respektive komponent påverkar prestanda på utsignalen. Därigenom erhålls ett mått på den maximala prestandaförbättring som kan uppnås om felet kan elimineras.This work considers behavior modeling of analog to digital converters with applications in the radio frequency range, including the field of telecommunication as well as test and measurement instrumentation, where the conversion from analog to digital signals often is a bottleneck in performance. The models are intended to post-process output data from the converter and thereby improve the performance of the digital signal. By building a model of practical converters and the way in which they deviate from ideal, imperfections can be corrected using post-correction methods. Behavior modeling implies generation of a suitable stimulus, capturing the output data, and characterizing a model. The demands on the test setup are high for converters in the radio frequency range. The test-bed used in this thesis is composed of commercial state-of-the-art instruments and components designed for signal conditioning and signal capture. Further, in this thesis, different stimuli are evaluated, theoretically as well as experimentally. There are a large number of available model structures for dynamic nonlinear systems. In order to achieve a parameter efficient model structure, a Volterra model was used as a starting-point, which can describe any weak nonlinear system with fading memory, such as analog to digital converters. However, it requires a large number of coefficients; for this reason the Volterra model was reduced to a model structure with fewer parameters, by comparing the symmetry properties of the Volterra kernels with the symmetries from other models. An alternative method is the Kautz-Volterra model, which has the same general properties as the Volterra model, but with fewer parameters. This thesis gives experimental results of the Kautz-Volterra model, which will be interesting to apply in a post-correction algorithm in the future. To cover behavior not explained by the dynamic nonlinear model, a complementary piecewise linear model component is added. In this thesis, a closed form solution to the estimation problem for both these model components is given. By gradually correcting for each component the performance will improve step by step. In this thesis, the relation between a given component and the performance of the converter is given, as well as potential for improvement of an optimal post-correction.
QC 20100629
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Hickish, Jack. „Digital signal processing methods for large-N, low-frequency radio telescopes“. Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:7d983fb3-9411-4906-92cd-70e2c1040b54.
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Current attempts to make precision measurements of the HI power spectrum at high redshifts have led to the construction of several low-frequency, large-N, interferometric arrays. The computational demands of digital correlators required by these arrays present a significant challenge. These demands stem from the treatment of radio telescopes as collections of two-element interferometers, which results in the need to multiply O(N2) pairs of antenna signals in an N-element array. Given the unparalleled flexibility offered by modern digital processing systems, it is apt to consider whether a different way of treating the signals from antennas in an array might be fruitful in current and future radio telescopes. Such methods potentially avoid the unfavourable N2 scaling of computation rate with array size. In this thesis I examine the prospect of using direct-imaging methods to map the sky without first generating correlation matrices. These methods potentially provide great computational savings by creating images using efficient, FFT-based algorithms. This thesis details the design and deployment of such a system for the Basic Element of SKA Training II (BEST-2) array in Medicina, Italy. Here the 32-antenna BEST-2 array is used as a test bed for comparison of FX correlation and direct-imaging systems, and to provide a frontend for a real-time transient event detection pipeline. Even in the case of traditional O(N2) correlation methods, signal processing algorithms can be significantly optimized to deliver large performance gains. In this thesis I present a new mechanism for optimizing the cross-correlation operation on Field Programmable Gate Array (FPGA) hardware. This implementation is shown to achieve a 75% reduction in multiplier usage, and has a variety of benefits over existing optimization strategies. Finally, this thesis turns its focus towards The Square Kilometre Array (SKA). When constructed, the SKA will be the world's largest radio telescope and will comprise a variety of arrays targeting different observing frequencies and science goals. The low-frequency component of the SKA (SKA-low) will feature ~250,000 individual antennas, sub-divided into a number of stations. This thesis explores the impact of the station size on the computational requirements of SKA-low, investigating the optimal array configuration and signal processing realizations.
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Whiting, Samuel. „Radio-Frequency Transmitter Geolocation Using Non-Ideal Received Signal Strength Indicators“. DigitalCommons@USU, 2018. https://digitalcommons.usu.edu/etd/7038.
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Locating a radio transmitter is important in a number of problems such as finding radio tags, people with radios, and devices that are collecting information in an unauthorized manner. Locating a radio transmitter is inherently difficult because the radio waves of concern are not in the visible spectrum, they reflect and distort easily, and they propagate at the speed of light.
A number of methods for locating transmitters are currently used, the majority of which require expensive hardware and extensive processing. This thesis presents a method of using simpler measurements to produce similar location estimates in order to augment or replace current systems. While other systems have significant advantages, the methods proposed in this thesis are advantageous because they only require easily-obtained measurements that are based on the observed power of the transmission.
The research uses simulations and experiments on real-world data collected locally to demonstrate the possibility of locating a transmitter using information of this type. The conclusion is that some methods are able to compensate for the difficulties in the problem more effectively and produce useful location estimates.
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Wilson, Derek Edwin. „A Pilot Survey for Astronomical Low Frequency Radio Transients“. Thesis, Virginia Tech, 2005. http://hdl.handle.net/10919/34715.
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Dispersed low-frequency radio astronomical pulses may result from exploding primordial
black holes, gamma ray bursts, supernovae, or mergers of exotic objects, but have not yet
been detected. Detection would be of great scientific significance because such events must
involve extreme physics. The transient nature of these events makes detection unlikely with
traditional instruments due to lack of sensitivity to single pulses and narrow field of view.
For this thesis, a low-frequency wide-bandwidth astronomical search instrument has been
developed as an alternative approach. This instrument consists of a single dipole which
yields all-sky field of view, albeit at reduced sensitivity. The spectrum from 37 - 55 MHz
is coherently digitized at 200 million samples per second, recorded, and analyzed off-line for
the presence of dispersed pulses. A preliminary survey has been made at a remote site in
western North Carolina. In a 20 minute observation, 9 detections greater than 6.5 occurred, corresponding to pulses of 20 ms duration and dispersion measures (DMs) ranging from 15 to 70 pc cm−3 . In addition, groups of pulses were detected ( 5) at DMs of 43.1, 52.1,
and 52.2 pc cm−3 . The possibility of association with known pulsars is considered; however,
it is also possible these are due simply to radio frequency interference. Improvements to this
instrument and survey technique are suggested.Master of Science
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Wong, K.-H. H. „Transmission of channel coded speech and data over mobile radio channels“. Thesis, University of Southampton, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.235340.
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Shahri, Javad Yazdani Kohneh. „High frequency digital power line transmission for terrestrial and marine networks“. Thesis, Lancaster University, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.288950.
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Law, Eugene L. „TELEMETRY RF SIGNAL BANDWIDTH; DEFINITIONS AND STANDARDS“. International Foundation for Telemetering, 1995. http://hdl.handle.net/10150/608400.
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International Telemetering Conference Proceedings / October 30-November 02, 1995 / Riviera Hotel, Las Vegas, NevadaThis paper will present and compare several definitions of telemetry radio frequency (RF) signal bandwidth. Measured spectra for different signals will be presented. The bandwidths of these signals will then be determined and measurement methods will be discussed. This discussion will include the effects of spectrum analyzer resolution bandwidth, video bandwidth and detector type. Finally, a proposed spectral mask will be discussed. This spectral mask can be used to calculate the required attenuation for a given frequency offset from the center frequency. The required attenuation is a function of the the bit rate or maximum frequency of interest and the transmitter power. This spectral mask is proposed to be part of the next edition of the Telemetry Standards, Inter-Range Instrumentation Group (IRIG) Standard 106.
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Nader, Charles. „Signal Shaping and Sampling-based Measurement Techniques for Improved Radio Frequency Systems“. Doctoral thesis, KTH, Signalbehandling, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-95404.
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Wireless communication systems are omnipresent in our day-to-day life, with high expectations regarding capacity, reliability and power efficiency. In order to satisfy the capacity and reliability expectations, today's wireless systems are adopting sophisticated modulation schemes, such as orthogonal frequency division multiplexing (OFDM), which shape today's wireless signals with large bandwidths and high crest factors. On top of that, it is anticipated that different wireless systems/standards will co-exist and share the same radio frequency (RF) front-end in order to reduce the network implementation cost. Such signals characteristics and systems coexistence put high requirements on the amplification stage which in best scenarios is considered weakly nonlinear. As a result, the power amplifier needs to be backed-off for linear operation. However, such power back-off reduces the operation's efficiency. Reducing the crest factor of the wireless signal and the possibility to linearize by means of digital pre-distortion the operation behavior of the power amplifier when operated near its maximum allowed continuous wave (CW) operating power range would lead to the optimal linearity and efficiency of operation. In order to achieve a good linearization performance, accurate baseband behavioral models are needed which requires measuring time domain signals whose spectra spread largely due to the nonlinear operation of the power amplifier. Such spectrum spreading, denoted by spectral regrowth, puts high requirements on today's sampling-based measurement systems as a trade-of between the sampling rate and amplitude resolution exists in today's generation of analog-to-digital converters, in addition to a limitation in the available analog bandwidth. Overcoming such measurement challenges could lead to the design of expensive measurement systems which is not favorable. In this thesis, the performance of RF transmitters is improved by combining the use of a smart crest factor reduction technique with an enhanced digital pre-distortion technique which allows operating the power amplifier near its CW 1-dB compression point, offering a significant increase in the efficiency of operation while satisfying the standard constraints on information error and spectral emission. Furthermore, the performance of RF measurement receivers is improved by reducing the requirements on the digital bandwidth by means of an evolved harmonic sampling technique, and by reducing the requirements on the analog bandwidth and design cost by means of a digital bandwidth interleaving technique and a signal separation technique based on an advanced sparse reconstruction methodology.Trådlösa kommunikationssystem förekommer överallt i vår vardag, med höga förväntningar på kapacitet, tillförlitlighet och energieffektivitet. För att uppfylla förväntningar på kapacitet och tillförlitlighet är dagens trådlösa system utrustade med avancerade modulationsmetoder, såsom Orthogonal Frequency Division Multiplexing (OFDM), vilket medför att dagens trådlösa signaler har stora bandbredder och höga toppfaktorer. Därutöver planeras det för att olika trådlösa system/standarder kommer att samexistera och samutnyttja komponenter i gränssnittet mot radiosignaler, s.k. RF front-end, för att därigenom minska kostnader för nätverk. Egenskaperna hos dessa signaler och samexisterande system ställer höga krav på förstärkarsteg som i bästa fall kan anses svagt olinjära. Som ett resultat av detta behöver effektförstärkaren arbetspunkt flyttas för förstärkaren skall arbeta i det linjära området, men en sådan förflyttning minskar systemets verkningsgrad. Genom att reducera toppfaktorn på den trådlösa signalen samt att linjärisera förstärkarsteget genom digital förförvrängning, även kallad predistortion, hos effektförstärkaren när den drivs nära sin högsta tillåtna arbetspunkt för en kontinuerlig signal (CW) kan optimal linjäritet och effektiv drift erhållas. För att uppnå god linjäriseringsprestanda krävs noggranna modeller som beskriver beteende i basbandet. Att ta fram dessa modeller kräver tidsdomänmätningar av signaler vars spektra är bredbandiga, till stor del beroende på icke-linjär drift av effektförstärkaren. Bredbandiga spektra ställer höga krav på dagens samplande mätsystem i och med kompromissen mellan samplingsfrekvens och upplösning i amplitud finns i dagens generation av analog till digital omvandlare; dessutom finns en begränsning i tillgänglig analog bandbredd. Att lösa dessa utmanande mätproblem kan leda till utformning av dyra mätsystem vilket inte är önskvärt. I denna avhandling förbättras prestandan hos en radiosändare genom en kombination av smart toppfaktorreduktion och förbättrad digital predistortionsteknik som gör det möjligt att driva effektförstärkaren nära sin 1 dB kompressionspunkt, vilket erbjuder en betydande ökning av systemets verkningsgrad samtidigt som det uppfyller standarders krav avseende vektornoggrannhet och spektral spridning. Dessutom har prestandan på mätutrustningen för radiofrekvenser (RF) förbättras genom att minska kraven på digital bandbredd med hjälp av en nyutvecklad harmonisk samplingsteknik, och genom att minska kraven på den analoga bandbredden och konstruktionskostnad med hjälp av en teknik att intersekvensera signaler i den digitala frekvensdomänen samt med en signalseparationsteknik baserad på en avancerad rekonstruktionsmetod för glesa signaler.
QC 20120605
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Lintz, William A. „Radio frequency signal reception via distributed wirelessly networked sensors under random motion“. Monterey, Calif. : Naval Postgraduate School, 2009. http://edocs.nps.edu/npspubs/scholarly/dissert/2009/Sep/09Sep%5FLintz%5FPhD.pdf.
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Dissertation (Ph.D. in Electrical Engineering)--Naval Postgraduate School, September 2009.Dissertation supervisor: McEachen, John ; Tummala, Murali. "September 2009." Description based on title screen as viewed on November 5, 2009. Author(s) subject terms: Sensor Networks, Beamforming, Random Motion, Orientation Includes bibliographical references (p. 197-203). Also available in print.
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Maidana, Renan Guedes. „Outdoor localization system for mobile robots based on radio-frequency signal strength“. Pontif?cia Universidade Cat?lica do Rio Grande do Sul, 2018. http://tede2.pucrs.br/tede2/handle/tede/8140.
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Na ?rea da Rob?tica M?vel, o problema da localiza??o ? definido como a determina??o da posi??o e orienta??o de um rob? em um espa?o tri-dimensional atrav?s de informa??es de seus sensores. A solu??o mais comum para esse problema ? utilizar um receptor de GPS (doingl?s, Global Positioning System), que reporta posi??o absoluta com rela??o a um sistema de coordenadas fixo e centralizado na Terra. Por?m, o sinal de GPS ? muito afetado por condi??es ambientais e oclus?o de linha de vis?o, por vezes fornecendo estimativas de posi??o de baixa qualidade, se houverem .Com inspira??o nestes problemas, este projeto prop?e um sistema de localiza??o para ser usado por um rob? terrestre em um ambiente externo n?o-controlado, onde h? indisponibilidade de GPS ou que suas medidas s?o de baixa qualidade. Tendo em vista que sensores de baixo custo apresentam medi??es imprecisas devido a fatores ambientais (e.g. terreno acidentado), ? proposta a utiliza??o de pares receptor-transmissor de R?dio-Frequ?ncia, onde a medida do Indicador de Pot?ncia de Sinal Recebido ? usada para estimar as dist?ncias entre receptor e trans- missor, que s?o por sua vez usadas para posicionamento. Essa medida possuia vantagem de ser independente da ilumina??o do ambiente e do estado do terreno, que afetam outros m?todos de localiza??o como Odometria Visual ou por rodas. Um erro m?dio de posiciona- mento de 0.41m foi alcan?ado atrav?s da fus?o de odometria por rodas, velocidade angular de um girosc?pio e pot?ncia de sinal recebido, em um algoritmo de Filtro de Kalman Esten- dido Aumentado, comum a melhoria de 82.66% referente ao erro m?dio de 2.38 m obtido com um sensor GPS comum.
In the field of Mobile Robotics, the localization problem consists on determining a robot?s position and orientation in a three-dimensional space through sensor information. The most common solution to this problem is to employ a Global Positioning System receiver, also known as GPS, which reports absolute position in relation to an Earth-centered fixed coordinate system. However, GPS signals are greatly affected by atmospheric conditions and line-of-sight occlusion, sometimes providing very poor position estimates, if any at all. Inspired by these problems, this project proposes a localization system to be used by a robot in an uncontrolled outdoor environment, where GPS measurements are poor or unavailable. As common sensors provide inaccurate position estimates due to environmental factors (e.g. rough terrain), we propose the use of Radio-Frequency receiver-transmitter pairs, in which the Received Signal Strength Indicator is used for estimating the distances between receiver and transmitter, which in turn are used for positioning. This measurement has the advantage of being independent from lighting conditions or the state of the terrain, factors which affect other localization methods such as visual or wheel odometry. A mean positioning error of 0.41 m was achieved by fusing wheel odometry, angular velocity from a gyroscope and the received signal strength, in an Augmented Extended Kalman Filter algorithm, with an improvement of 82.66% relative to the mean error of 2.38 m obtained with a common GPS sensor.
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O'Brien, Kathleen. „Inductively coupled radio frequency power transmission system for wireless systems and devices /“. Aachen : Shaker, 2007. http://bvbr.bib-bvb.de:8991/F?func=service&doc_library=BVB01&doc_number=015959229&line_number=0001&func_code=DB_RECORDS&service_type=MEDIA.
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Bland, Denise. „Alias-free signal processing of nonuniformly sampled signals“. Thesis, University of Westminster, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.322992.
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Abdullah, S. N. „Data transmission at 9600 bit/sec over an HF radio link“. Thesis, Loughborough University, 1986. https://dspace.lboro.ac.uk/2134/7432.
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The thesis is concerned with serial data transmission at 9600 bit/sec over a voiceband channel, where the main impairments are additive noise and intersymbol interference, and the latter varles slowly with time. The thesis includes a brief description of the ionospheric propagation medium and presents an equivalent baseband model of the HF channel, suitable for computer simulation of quadrature amplitude modulation (QAM) systems. A study of 16-point QAM signals transmitted over voiceband HF channels is then carr-iod out usj-ng the given channel model. Several cost effective near-maximum-likelihood detection processes have been developed for HF modems. Each detector is here preceded by an adaptive linear filter that is adjusted to make the sampled impulse response of the channel and filter minimum phase. These detectors require an accurate knowledge of the sampled impulse response of the channel, if their full potential is to be achieved. The results of computer-simulation tests on the near-maximum-likelihood detectors are given, where these tests assume that other receiver operations such as channel estimation and adaptive linear filtering, together with element timing synchronisation and Doppler shift correction, are carried out perfectly. A recently developed HF channel estimator employing a simple feedforward transversal-filter and requiring knowledge of the number of skywaves is next investigated and a starting up procedure is developed for such an estimator. The technique is then made fully adaptive in the sense that it continues to operate correctly when the number of skywaves changes. Results of computer simulation tests are then presented showing the performance of the above detectors when operating with a channel estimator and adaptive linear filtering. Finally modem synchronisation is studied and various techniques of element timing and carrier frequency synchronisation are proposed.
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Moustakidis, Iordanis Vlasios. „Detection of erosion/deposition depth using a low frequency passive radio frequency identification (rfid) technology“. Thesis, University of Iowa, 2012. https://ir.uiowa.edu/etd/1490.
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This thesis presents an experimental study both in the laboratory and field to develop and test a method for continuously measuring and monitoring scour using an automated identification technology known as Radio Frequency Identification (RFID). RFID systems consist of three main components, namely (a) the reader which controls the system, (b) the transponder (derived from transmitter/responder) that transmits data to the reader and (c) the excitation antenna that allows the communication between the reader and the transponder.
The study provides an insight into the RFID technology and develops the framework for using this technology to eventually address two central themes in river mechanics and sediment transport; (a) the determination of the active layer thickness and (b) the scour/deposition depth around a hydraulic structure. In particular, this study develops the methodology for relating the signal strength of a radio frequency (RF) device with the distance between an excitation antenna and the RF device.
The experiments presented herein are classified into two main groups, (1) the laboratory and (2) the RF signal vs. the detection distance experiments (field experiments). The laboratory experiments were designed to understand the effect of key RFID parameters (e.g., transponder orientation with respect to the excitation antenna plane, maximum antenna-transponder detection distance), measured in terms of the transponder return RF signal strength for various antenna-transponder distances, transponder orientations with respect to the excitation antenna plane and different mediums in between the excitation antenna and the transponder, on the overall performance of the RFID system. On the other hand, the RF signal vs. the detection distance experiments were based on the results obtained during the laboratory experiments and focused on developing calibration curves by relating the transponder return RF signal strength with the distance between the excitation antenna and a transponder.
The laboratory results show that the dominant RFID parameters affecting the system performance are (a) the transponder orientation towards the excitation antenna plane and (b) the medium type in between the excitation antenna and the transponder. The differences in reading distances were attributed to the transponder inner antenna type, while the effect of the medium was related with the void ratio, where higher porosity materials have, less RF signal strength decay. The parameter that governs the RF signal strength decay was found to be the distance between the excitation antenna and the transponder (erosion process experiments). The RF signal strength decays almost linearly with distance, while the rate of the RF signal strength decay is controlled by the material type in between the excitation antenna and the transponder (deposition process experiments).
The RF signal vs. the detection distance experiments demonstrate that the reading distance of the RFID system can be significantly increased by using a custom made excitation antenna. The custom made excitation antenna not only increases the reading distance between the antenna and the transponder to nearly 20 ft., but also allows the user to manipulate the excitation antenna's shape and size to meet the specific landscape requirements at the monitoring site.
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Koike, Toshiaki. „Space-time-frequency signal processing for spectrum-efficient multiple-antenna wireless transmission systems“. 京都大学 (Kyoto University), 2005. http://hdl.handle.net/2433/144509.
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Kyoto University (京都大学)0048
新制・課程博士
博士(情報学)
甲第11908号
情博第180号
新制||情||40(附属図書館)
23688
UT51-2005-N742
京都大学大学院情報学研究科通信情報システム専攻
(主査)教授 吉田 進, 教授 酒井 英昭, 教授 佐藤 亨
学位規則第4条第1項該当
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Chu, Xiaoli. „Ultra-wideband direct-sequence impulse radio wireless communications /“. View abstract or full-text, 2005. http://library.ust.hk/cgi/db/thesis.pl?ELEC%202005%20CHU.
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DeLong, Brock J. „Integration of Radio Frequency Harvesting with Low Power Sensors“. The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu152408949118599.
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Foster, Griffin. „Large-N correlator systems for low frequency radio astronomy“. Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:2bca41ff-ec75-4a41-a634-c5bbbceae434.
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Low frequency radio astronomy has entered a second golden age driven by the development of a new class of large-N interferometric arrays. The low frequency array (LOFAR) and a number of redshifted HI Epoch of Reionization (EoR) arrays are currently undergoing commission and regularly observing. Future arrays of unprecedented sensitivity and resolutions at low frequencies, such as the square kilometer array (SKA) and the hydrogen epoch of reionization array (HERA), are in development. The combination of advancements in specialized field programmable gate array (FPGA) hardware for signal processing, computing and graphics processing unit (GPU) resources, and new imaging and calibration algorithms has opened up the oft underused radio band below 300 MHz. These interferometric arrays require efficient implementation of digital signal processing (DSP) hardware to compute the baseline correlations. FPGA technology provides an optimal platform to develop new correlators. The significant growth in data rates from these systems requires automated software to reduce the correlations in real time before storing the data products to disk. Low frequency, widefield observations introduce a number of unique calibration and imaging challenges. The efficient implementation of FX correlators using FPGA hardware is presented. Two correlators have been developed, one for the 32 element BEST-2 array at Medicina Observatory and the other for the 96 element LOFAR station at Chilbolton Observatory. In addition, calibration and imaging software has been developed for each system which makes use of the radio interferometry measurement equation (RIME) to derive calibrations. A process for generating sky maps from widefield LOFAR station observations is presented. Shapelets, a method of modelling extended structures such as resolved sources and beam patterns has been adapted for radio astronomy use to further improve system calibration. Scaling of computing technology allows for the development of larger correlator systems, which in turn allows for improvements in sensitivity and resolution. This requires new calibration techniques which account for a broad range of systematic effects. And, a deep integration between DSP hardware and software data reduction into a single backend.
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Jang, Won Suk. „Embedded system for construction material tracking using combination of radio frequency and ultrasound signal“. College Park, Md.: University of Maryland, 2007. http://hdl.handle.net/1903/7683.
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Thesis (Ph. D.) -- University of Maryland, College Park, 2007.Thesis research directed by: Dept. of Civil and Environmental Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Fioravanti, Paolo. „Large signal design of silicon field effect transistors for linear radio frequency power amplifiers“. Thesis, De Montfort University, 2006. http://hdl.handle.net/2086/13294.
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Sinha, Amit Kumar. „An investigation of Marconi's first transatlantic experiment in Newfoundland to find the correct frequency of transmission (Guglielmo Marconi)“. Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0031/MQ47478.pdf.
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Nilsson, Anders. „Offset-PLL based frequency up-conversion for low spurious transmission“. Thesis, Linköping University, Department of Electrical Engineering, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-1838.
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The goal of this final year project is to investigate various techniques to up-convert a baseband signal into radio frequency signals, and to investigate the practical problems encountered in an offset phase locked loop design by implementation.
Phase locked loops are commonly used in radio transmitters and receivers to generate accurate RF signals from a low-frequency reference. This thesis will highlight some of the problems and strengths of various up-conversion schemes, and suggest an offset-PLL architecture free from many of those problems.
An offset-PLL is often used in mobile communication systems where the required levels of out of band transmission are tough and the use of superheterodyne up-conversion cannot be used due to spectrum or bandwidth requirements.
However a drawback of an offset-PLL is the high locking time; this can render the offset-PLL useless in TDMA communication systems. This problem among others has been studied theoretically as well as practically on an actual implementation of an offset-PLL for mobile communications. The offset-PLL was designed and manufactured as part of this project.
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Flowers, Bryse Austin. „Adversarial RFML: Evading Deep Learning Enabled Signal Classification“. Thesis, Virginia Tech, 2019. http://hdl.handle.net/10919/91987.
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Deep learning has become an ubiquitous part of research in all fields, including wireless communications. Researchers have shown the ability to leverage deep neural networks (DNNs) that operate on raw in-phase and quadrature samples, termed Radio Frequency Machine Learning (RFML), to synthesize new waveforms, control radio resources, as well as detect and classify signals. While there are numerous advantages to RFML, this thesis answers the question "is it secure?" DNNs have been shown, in other applications such as Computer Vision (CV), to be vulnerable to what are known as adversarial evasion attacks, which consist of corrupting an underlying example with a small, intelligently crafted, perturbation that causes a DNN to misclassify the example. This thesis develops the first threat model that encompasses the unique adversarial goals and capabilities that are present in RFML. Attacks that occur with direct digital access to the RFML classifier are differentiated from physical attacks that must propagate over-the-air (OTA) and are thus subject to impairments due to the wireless channel or inaccuracies in the signal detection stage. This thesis first finds that RFML systems are vulnerable to current adversarial evasion attacks using the well known Fast Gradient Sign Method originally developed for CV applications. However, these current adversarial evasion attacks do not account for the underlying communications and therefore the adversarial advantage is limited because the signal quickly becomes unintelligible. In order to envision new threats, this thesis goes on to develop a new adversarial evasion attack that takes into account the underlying communications and wireless channel models in order to create adversarial evasion attacks with more intelligible underlying communications that generalize to OTA attacks.Master of Science
Deep learning is beginning to permeate many commercial products and is being included in prototypes for next generation wireless communications devices. This technology can provide huge breakthroughs in autonomy; however, it is not sufficient to study the effectiveness of deep learning in an idealized laboratory environment, the real world is often harsh and/or adversarial. Therefore, it is important to know how, and when, these deep learning enabled devices will fail in the presence of bad actors before they are deployed in high risk environments, such as battlefields or connected autonomous vehicle communications. This thesis studies a small subset of the security vulnerabilities of deep learning enabled wireless communications devices by attempting to evade deep learning enabled signal classification by an eavesdropper while maintaining effective wireless communications with a cooperative receiver. The primary goal of this thesis is to define the threats to, and identify the current vulnerabilities of, deep learning enabled signal classification systems, because a system can only be secured once its vulnerabilities are known.
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O'Brien, Kathleen [Verfasser]. „Inductively Coupled Radio Frequency Power Transmission System for Wireless Systems and Devices / Kathleen O'Brien“. Aachen : Shaker, 2007. http://d-nb.info/1166516717/34.
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Gendron, Paul John. „A comparison of digital beacon receiver frequency estimators“. Thesis, This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-09292009-020307/.
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Sim, Zhi Wei. „Radio frequency energy harvesting for embedded sensor networks in the natural environment“. Thesis, University of Manchester, 2012. https://www.research.manchester.ac.uk/portal/en/theses/radio-frequency-energy-harvesting-for-embedded-sensor-networks-in-the-natural-environment(b0f3db83-8a82-4376-841b-d79bcd0d16ae).html.
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The agricultural sector is an emerging application area for Wireless Sensor Networks (WSNs). This requires sensor nodes to be deployed in the outdoor environment so as to monitor pertinent natural features, such as soil condition or pest infestation. Limited energy supply and subsequent battery replacement are common issues for these agricultural sensor nodes. One possible solution is to use energy harvesting, where the ambient energy is extracted and converted into usable electrical form to energise the wireless sensors. The work presented in this thesis investigates the feasibility of using Radio Frequency (RF) energy harvesting for a specific application; that is powering a generic class of wireless ground-level, agricultural sensor networks operating in an outdoor environment. The investigation was primarily undertaken through a literature study of the subject. The first part of the thesis examines several energy harvesting/ wireless energy transfer techniques, which may be applicable to power the targeted agricultural WSN nodes. The key advantages and limitations of each technique are identified, and the rationale is being given for selecting far-field RF energy harvesting as the investigated technique. It is then followed by a theoretical-based system analysis, which seeks to identify all relevant design parameters, and to quantify their impact on the system performance. An RF link budget analysis was also included to examine the feasibility of using RF energy harvesting to power an exemplar WSN node - Zyrox2 Bait Station. The second part of the thesis focuses on the design of two energy harvesting antennas. The first design is an air-substrate-based folded shorted patch antenna (FSPA) with a solid ground plane, while the second design is a similar FSPA structure with four pairs of slot embedded into its ground plane. Both antennas were simulated, fabricated and tested inside an anechoic chamber, and in their actual operating environment - an outdoor field. In addition, a power harvester circuit, built using the commercially available off-the-shelf components, was tested in the laboratory using an RF signal generator source. The results from both the laboratory and field trial were analysed. The measurement techniques used were reviewed, along with some comments on how to improve them. Further work on the RF energy harvester, particularly on the improvement of the antenna design must be carried out before the feasibility and viable implementations for this application can be definitively ascertained.
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Qian, Hua. „Power Efficiency Improvements for Wireless Transmissions“. Diss., Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/11649.
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Many communications signal formats are not power efficient because of their large peak-to-average power ratios (PARs). Moreover, in the presence of nonlinear devices such as power amplifiers (PAs) or mixers, the non-constant-modulus signals may generate both in-band distortion and out-of-band interference. Backing off the signal to the linear region of the device further reduces the system power efficiency. To improve the power efficiency of the communication system, one can pursue two approaches: i) linearize the PA; ii) reduce the high PAR of the input signal.
In this dissertation, we first explore the optimal nonlinearity under the peak power constraint. We show that the optimal nonlinearity is a soft limiter with a specific gain calculated based on the peak power limit, noise variance, and the probability density function of the input amplitude. The result is also extended to the fading channel case.
Next, we focus on digital baseband predistortion linearization for power amplifiers with memory effects. We build a high-speed wireless test-bed and carry out digital baseband predistortion linearization experiments. To implement adaptive PA linearization in wireless handsets, we propose an adaptive digital predistortion linearization architecture that utilizes existing components of the wireless transceiver to fulfill the adaptive predistorter training functionality.
We then investigate the topic of PAR reduction for OFDM signals and forward link CDMA signals. To reduce the PAR of the OFDM signal, we propose a dynamic selected mapping (DSLM) algorithm with a two-buffer structure to reduce the computational requirement of the SLM method without sacrificing the PAR reduction capability. To reduce the PAR of the forward link CDMA signal, we propose a new PAR reduction algorithm by introducing a relative offset between the in-phase branch and the quadrature branch of the transmission system.
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Peng, Song, Zhang XiaoLin, Cao Xue und Qi Xia. „THE APPLICATION OF DIGITAL DEMODULATION TECHNIQUE FOR FREQUENCY MODULATION SIGNAL IN TELEMETRY RECEIVER“. International Foundation for Telemetering, 2004. http://hdl.handle.net/10150/604956.
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International Telemetering Conference Proceedings / October 18-21, 2004 / Town & Country Resort, San Diego, CaliforniaCombined with an example of digital telemetry receiver design, this paper mainly discusses the application of software radio in telemetry receiver. The paper begins with an introduction of applying high efficiency digital filter and math analysis in quadrature digital frequency modulation and demodulation to digital frequency conversion technique. Next, Simulink/Matlab is used to simulate digital telemetry receiver. The method of simulation, analysis and calculation of performance and result of simulation are all available. In the end, the paper discusses digital telemetry receiver design and implement by making use of software radio technique, the circuits apply HSP50214 chip of Intersil Co., CPLD implements of Altera Co. and PC Bus. The sample is an expansion card for personal computer. Result of test, performance of the receiver and conclusion are given out, which show fine performance of receiver and can be apply to practice. The lever of this technology has reached first class in the world.
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Toh, Leng Huei. „A follow-up study on wireless power transmission for unmanned air vechicles [sic vehicles]“. Thesis, Monterey, Calif. : Naval Postgraduate School, 2007. http://bosun.nps.edu/uhtbin/hyperion-image.exe/07Dec%5FToh.pdf.
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Thesis (M.S. in Electrical Engineering)--Naval Postgraduate School, December 2007.Thesis Advisor(s): Jenn, David C. "December 2007." Description based on title screen as viewed on January 24, 2008. Includes bibliographical references (p. 85-88). Also available in print.
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Sobering, Ian David. „Mitigating oscillator pulling due to magnetic coupling in monolithic mixed-signal radio-frequency integrated circuits“. Thesis, Kansas State University, 2014. http://hdl.handle.net/2097/19755.
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Master of ScienceDepartment of Electrical and Computer Engineering
W. B. Kuhn
An analysis of frequency pulling in a varactor-tuned LC VCO under coupling from an on-chip PA is presented. The large-signal behavior of the VCO's inversion-mode MOS varactors is outlined, and the susceptibility of the VCO to frequency pulling from PA aggressor signals with various modulation schemes is discussed. We show that if the aggressor signal is aperiodic, band-limited, or amplitude-modulated, the varactor-tuned LC VCO will experience frequency pulling due to time-modulation of the varactor capacitance. However, if the aggressor signal has constant-envelope phase modulation, VCO pulling can be eliminated, even in the presence of coupling, through careful choice of VCO frequency and divider ratio. Additional mitigation strategies, including new inductor topologies and system-level architectural choices, are also examined. The analysis is then applied to improve a fully-integrated half-duplex UHF micro- transceiver in which signal coupling between the LO and PA caused frequency pulling that prevented the use of QPSK signaling at certain data rates. We determine that a VCO operating at 4x transmit frequency will be naturally insensitive to pulling from QPSK signals. To validate the proposed solution, a prototype IC containing a pair of QPSK transmitters with integrated 100mW Class-C PAs was designed and fabricated in 0.18um SOI. The transmitters--one utilizing a 2x VCO, one utilizing a 4x VCO-- were designed to closely match the performance of the original microtransceiver when transmitting QPSK data. The transmitter with the 2x VCO experienced frequency pulling from the PA while transmitting QPSK data, but the transmitter with the 4x VCO did not, thereby confirming the analysis in this work. A revision of the microtransceiver was designed in 0.5 [mu]m SOS utilizing an off- chip PA inductor to reduce signal coupling with the VCO. A second revision of the microtransceiver with two prototype transmitters was designed in 0.25 [mu]m SOS uti- lizing 4x VCOs and figure-8 VCO inductors for maximum insensitivity to pulling from QPSK and band-limited modulation, as well as other design improvements that leverage the higher f[subscript]t of the smaller process. Both revisions also include a hardware FSK modulator, a new charge pump, and a redesigned fractional-N synthesizer to attenuate a divided-reference spur in the IF output. These revisions of the radio will enable future researchers to focus on system-level applications where highly-integrated medium-power transceivers with fully-functioning IQ modulation are needed.
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Hetzel, Simon Andrew. „Power efficient linear transmitters and the LINC technique“. Thesis, University of Bristol, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.261286.
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Park, Youngcheol. „Dual-Band Transmitters Using Digitally Predistorted Frequency Multipliers for Reconfigurable Radios“. Diss., Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/5107.
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The objective of the proposed research is to develop simplified reconfigurable transmission systems with frequency multipliers for the transmission of complex modulated signals. Because they rely on nonlinear properties, frequency multiplier-based transmission systems require proper linearization techniques and accurate modeling of the signal transfer function. To accomplish these two goals, the author has developed techniques to model and linearize frequency multipliers and to digitize feedback signals for nonlinear characterization.
First, adaptive predistortion techniques and zonal transfer theories have been developed for modeling and linearization. The predistortion system has been verified by applying an IS-95B signal to various frequency multipliers built by the author.
Second, because the output signals at higher harmonic zones occupy wider frequency bandwidths than the signal in the fundamental zone does and thus make it harder to use traditional sampling techniques, a simplified but effective method called the sub-Nyquist sampling rate was developed and verified.
Third, two methods for reconfigurable transmitters using frequency multipliers in conjunction with digital predistortion linearizers were developed. Both methods make it possible to transmit complex signals via frequency multipliers by using dual-band transmission systems that incorporate frequency multipliers that are based on linearization techniques. One of these methods uses a circuit topology that can be switched between a fundamental-mode in-phase combined amplifier and a push-push frequency doubler using input phasing. The second suggested method uses a fundamental-frequency power amplifier followed by a varactor multiplier that can be bypassed with an RF switch.
This work will contribute to the development of low-cost and size-effective reconfigurable transmission systems because it requires fewer transmitting components and needs less sampling of the feedback networks.
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Nygaard, Erich Johannes. „Signal Transport and RF over Fiber Design for ALPACA“. BYU ScholarsArchive, 2020. https://scholarsarchive.byu.edu/etd/8753.
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The design of the RF over fiber signal transport system for the ALPACA receiver is described, with particular attention to the strict noise requirements as well as dynamic range considerations. Also discussed are analytical tools for analyzing dynamic range in the context of RFI-rich radio astronomy observational settings, including formulas for maximum interference to noise ratios and a simulation framework for predicting distortion levels. Phase and gain stability measurements of the signal transport system are presented, including the effects of the multi-strand armored fiber optic cable. The resulting system meets design requirements, with equivalent noise temperature below 900 K in 90° F ambient air, resulting in less than 1 K contribution to the system noise temperature. Typical gain is 31-37 dB, and gain differences between channels are stable within 0.25 dB in 90° F conditions. Phase drift between channels due to electronics remains below 1° at room temperature, and below 1.3° in a warm environment. The fiber optic cable is predicted to cause phase changes between channels of no more than 1.3° per °C. Typical spurious free dynamic range is 99 dB·Hz^(⅔), and distortion levels for normal RFI conditions at Arecibo are expected to be 28 dB below the system noise floor.