Dissertations / Theses on the topic 'Radio frequency'
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1
Ker, Louise Moira. "Radio AGN evolution with low frequency radio surveys." Thesis, University of Edinburgh, 2013. http://hdl.handle.net/1842/7616.
Abstract:
Supermassive black holes are leading candidates for the regulation of galaxy growth and evolution over cosmic time, via ‘feedback’ processes, whereby outflows from the Active Galactic Nuclei (AGN) halt star formation within the galaxy. AGN feedback is generally thought to occur in two modes, high-excitation (HERG, or ‘quasar-mode’) and low-excitation (LERG or ’radio-mode’) each having a different effect on the host galaxy. LERGs curtail the growth of the most massive galaxies, whereas HERGs are thought to be activated by mergers/interactions, switching off star formation at high redshift. A critical problem in current extragalactic astrophysics lies in understanding the precise physical mechanisms by which these feedback processes operate, and how they evolve over cosmic time. Radio-loud AGN are an essential tool for studying major feedback mechanisms, as they are found within the largest ellipticals, and hence are beacons for the most massive black holes across the bulk of cosmic time. In this thesis I develop and study existing complete radio samples with extensive new multi-wavelength data in the radio, optical and infrared, aiming to investigate the evolution of AGN feedback modes, and methods to locate and study such systems at the very highest redshifts. This will serve to inform further studies of radio-AGN planned with next generation radio instruments such as the LOw Frequency ARray (LOFAR). Very few radio-loud AGN systems are currently known at high redshifts, and the effectiveness of traditional high redshift selection techniques, such as selection based on steep spectral index, have not been well quantified. A purely evidence-based approach to determining the efficiency of various high redshift selection techniques is presented, using nine highly spectroscopically complete radio samples; although weak correlations are confirmed between spectral index and linear size and redshift, selection first of infrared-faint radio sources remains by far the most efficient method of selecting high-z radio galaxies from complete samples. Radio spectral curvature in four of the complete samples is analysed and the effect of radio spectral shape on the measurement of the radio luminosity function (RLF) of steep-spectrum radio sources is investigated. Below z=1, curvature has negligible effect on the measurement of the RLF, however at higher redshifts, where source numbers are low, the shape of the radio spectrum should be taken into account, as individual source luminosities can change up to 0.1-0.2 dex, and this can in some cases introduce errors in space density measurements of up to a factor of 2-3 where source numbers are low. Building upon these samples, the very first independent determinations of the separate RLFs for high and low excitation radio sources across the bulk of cosmic time are made, out to z=1. Here it is shown that HERGs show very clear signs of strong evolution, in line with theoretical predictions. LERGs also show some very weak evolution with redshift, showing increases in space density of typically around a factor of 2. These measurements are also used to estimate the contribution of LERGs, which typically show weak or no emission lines to the ‘missing redshift’ population, which are sources within the complete samples not identifiable spectroscopically. Complementary to this, a pilot study is presented in selecting ‘missing redshift’ sources which are classed as infra-red faint (IFRS), which show no optical or near-IR identification, and are compact in the radio. Follow up spectroscopy on these candidate high z sources detected no line emission. Finally, work carried out towards the testing and commissioning of the new LOFAR telescope is presented. The findings from this thesis will serve to both streamline and inform high redshift radio-AGN searches and studies planned to be carried out with LOFAR and other multi-wavelength complementary surveys in the near future, and help to open up an as yet unexplored epoch in radio-AGN formation and evolution.
2
Finlay, Chris. "Radio Frequency Interference: Simulations for Radio Interferometry Arrays." Master's thesis, Faculty of Science, 2021. http://hdl.handle.net/11427/33716.
Abstract:
Radio Frequency Interference (RFI) is a massive problem for radio observatories around the world. Due to the growth of telecommunications and air travel RFI is increasing exactly when the world's radio telescopes are increasing significantly in sensitivity, making RFI one of the most pressing problems for astronomy in the era of the Square Kilometre Array (SKA). Traditionally RFI is dealt with through simple algorithms that remove unexpected rapid changes but the recent explosion of machine learning and artificial intelligence (AI) provides an exciting opportunity for pushing the state-of-the-art in RFI excision. Unfortunately, due to the lack of training data for which the true RFI contamination is known, it is impossible to reliably train and compare machine learning algorithms for RFI excision on radio telescope arrays currently. To address this stumbling block we present RFIsim, a radio interferometry simulator that includes the telescope properties of the MeerKAT array, a sky model based on previous radio surveys coupled with an RFI model designed to reproduce actual RFI seen at the MeerKAT site. We perform an indepth comparison of the simulator results with real observations using the MeerKAT telescope and show that RFIsim produces visibilities that mimic those produced by real observations very well. Finally, we describe how the data was key in the development of a new state-of-the-art deep learning RFI flagging algorithm in Vafaei et al. (2020.) [69] In particular, this work demonstrates that transfer learning from simulation to real data is an effective way to leverage the power of machine learning for RFI flagging in real-world observatories.
3
Shenouda, Hany H. "An agile frequency synthesizer for frequency hopping radio." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0016/MQ49683.pdf.
4
Chen, Bing-Hung. "Inductively coupled radio-frequency discharges." Thesis, University of Oxford, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.244566.
5
Heikkinen, Jouko. "TELEMETRY AND RADIO FREQUENCY IDENTIFICATION." International Foundation for Telemetering, 1999. http://hdl.handle.net/10150/607334.
Abstract:
International Telemetering Conference Proceedings / October 25-28, 1999 / Riviera Hotel and Convention Center, Las Vegas, NevadaComparison of short-range telemetry and radio frequency identification (RFID) systems reveals that they are based on very similar operating principles. Combining the identification and measurement functions into one transponder sensor offers added value for both RFID and telemetry systems. The presence of a memory (e.g. FRAM) in the transponder, required for ID information, can also be utilized for storing measurement results. For passive transponders low power consumption is one of the main objectives. Wireless power transfer for passive transponder sensors together with above aspects concerning a combined telemetry and identification system are discussed.
6
Andrews, Seth Dixon. "Extensions to Radio Frequency Fingerprinting." Diss., Virginia Tech, 2019. http://hdl.handle.net/10919/95952.
Abstract:
Radio frequency fingerprinting, a type of physical layer identification, allows identifying wireless transmitters based on their unique hardware. Every wireless transmitter has slight manufacturing variations and differences due to the layout of components. These are manifested as differences in the signal emitted by the device. A variety of techniques have been proposed for identifying transmitters, at the physical layer, based on these differences. This has been successfully demonstrated on a large variety of transmitters and other devices. However, some situations still pose challenges:
Some types of fingerprinting feature are very dependent on the modulated signal, especially features based on the frequency content of a signal. This means that changes in transmitter configuration such as bandwidth or modulation will prevent wireless fingerprinting. Such changes may occur frequently with cognitive radios, and in dynamic spectrum access networks. A method is proposed to transform features to be invariant with respect to changes in transmitter configuration. With the transformed features it is possible to re-identify devices with a high degree of certainty.
Next, improving performance with limited data by identifying devices using observations crowdsourced from multiple receivers is examined. Combinations of three types of observations are defined. These are combinations of fingerprinter output, features extracted from multiple signals, and raw observations of multiple signals. Performance is demonstrated, although the best method is dependent on the feature set. Other considerations are considered, including processing power and the amount of data needed.
Finally, drift in fingerprinting features caused by changes in temperature is examined. Drift results from gradual changes in the physical layer behavior of transmitters, and can have a substantial negative impact on fingerprinting. Even small changes in temperature are found to cause drift, with the oscillator as the primary source of this drift (and other variation) in the fingerprints used. Various methods are tested to compensate for these changes. It is shown that frequency based features not dependent on the carrier are unaffected by drift, but are not able to distinguish between devices. Several models are examined which can improve performance when drift is present.Doctor of Philosophy
Radio frequency fingerprinting allows uniquely identifying a transmitter based on characteristics of the signal it emits. In this dissertation several extensions to current fingerprinting techniques are given. Together, these allow identification of transmitters which have changed the signal sent, identifying using different measurement types, and compensating for variation in a transmitter's behavior due to changes in temperature.
7
Viyyure, Uday Kiran Varma. "Frequency Assignments in Radio Networks." Kent State University / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=kent1209060158.
8
Fernandes, Rui Miguel Félix. "Object signature in radio frequency." Master's thesis, Universidade de Aveiro, 2014. http://hdl.handle.net/10773/13708.
Abstract:
Mestrado em Engenharia Eletrónica e TelecomunicaçõesThe RF signature can be consider as a fingerprint of an object when submitted to electromagnetic radiation. Based on this concept, the initial goal of this work was to elaborate a comparative analysis of the Radio Frequency signature of different materials. Through the design of a prototype based on an adapted Wi-Fi network was developed an innovative system capable of distinguishing materials with the analysis of their interference in the propagated channel. In order to refine this distinction was utilized a signal processing tool, the Wavelet Transform. This technique serve as support tool of the system for a better differentiation of the studied targets. The versatility of this concept was proved through the analysis of signatures of static targets like metal, wood and plastic, as well as moving targets, giving the example of a moving human. Due to the promising results obtained, the initial objective of the work was expanded being also presented in this document the concept of intruder detection through a Wi-Fi network by the analysis of the Wavelet coefficients.
A Assinatura em Rádio Frequência pode ser considerada como a impressão digital que um objeto manifesta quando submetido a radiação eletromagnética. O objetivo inicial deste trabalho era a elaboração de uma análise comparativa das assinaturas em Rádio Frequência de diferentes materiais. Tendo por base uma rede Wi-Fi adaptada, foi desenvolvido um sistema inovador capaz de distinguir materiais pela análise da interferência dos mesmos no canal de propagação. Com vista a melhorar o desempenho do protótipo inicial, o sinal recebido foi processado através da Transformada de Wavelet. Esta técnica serviu como ferramenta de suporte do sistema para a obtenção de uma diferenciação mais clara dos alvos estudados. Demonstrando a versatilidade deste conceito foram avaliadas as assinaturas de alvos estáticos como o metal, madeira e plástico bem como de alvos móveis dando, como exemplo, uma pessoa em movimento. Devido aos resultados promissores obtidos, o objetivo inicial do sistema foi alargado estando também presente neste documento o conceito de deteção de intrusos através de uma rede Wi-Fi pela análise dos coeficientes de Wavelet.
9
Matarrese, Vincent D. "Tapered radio frequency transmission lines." PDXScholar, 1992. https://pdxscholar.library.pdx.edu/open_access_etds/4329.
Abstract:
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.
10
Blackard, Kenneth Lee. "Measurements and models of radio frequency impulsive noise inside buildings." Thesis, This resource online, 1991. http://scholar.lib.vt.edu/theses/available/etd-08182009-040318/.
11
Kunselman, Gary L. "Radio frequency power amplifiers for portable communication systems." Thesis, Virginia Tech, 1992. http://hdl.handle.net/10919/41493.
Abstract:
Portable communication systems require, in part, high-efficiency radio frequency power amplifiers (RF PA) if battery lifetime is to be conserved. Conventional amplifier classifications and definitions are presented in a unified and concise format. The Bipolar Junction Transistor (BJT) and Metal-Semiconductor Field Effect Transistor (MESFET) are evaluated as active devices in high-efficiency RF PA designs. Two amplifier classes (class CE and class F) meet the system requirements of an 850 MHz operating frequency, a power output of 3 W, a battery supply voltage of 9 Vdc, and a sinusoidal-type signal to be amplified. Both classes are evaluated through recent research literature and simulated using the PSpice® computer simulation program. Class CE and class F are found to provide efficiencies exceeding 80 percent under the given system constraints.Master of Science
12
Bracht, Roger, Jeff Dimsdle, Dave Rich, and Frank Smith. "RADIO FREQUENCY OVERVIEW OF THE HIGH EXPLOSIVE RADIO TELEMETRY PROJECT." International Foundation for Telemetering, 1998. http://hdl.handle.net/10150/607352.
Abstract:
International Telemetering Conference Proceedings / October 26-29, 1998 / Town & Country Resort Hotel and Convention Center, San Diego, CaliforniaHigh explosive radio telemetry (HERT) is a project that is being developed jointly by Los Alamos National Laboratory and AlliedSignal FM&T. The ultimate goal is to develop a small, modular telemetry system capable of high-speed detection of explosive events, with an accuracy on the order of 10 nanoseconds. The reliable telemetry of this data, from a high-speed missile trajectory, is a very challenging opportunity. All captured data must be transmitted in less than 20 microseconds of time duration. This requires a high bits/Hertz microwave telemetry modulation code to insure transmission of the data within the limited time interval available.
13
Raspopoulos, Marios. "Radio propagation in frequency selective buildings." Thesis, University of Surrey, 2007. http://epubs.surrey.ac.uk/843209/.
Abstract:
Predicting and improving Radio propagation conditions has been a major topic of research since wireless communications started to emerge. The aim is to increase signal coverage and reliability, meet the increased traffic demands and provide high quality signal to the higher levels of the OSI model. Moreover, the coexistence of various wireless networks in a wireless communication environment, operating on various frequency bands increases the need for a frequency selective solution for improving radio propagation conditions of the various networks. For this reason, this work proposes a novel way to improve and controllably manipulate radio propagation by transforming the building interfaces into frequency selective. Naturally, buildings can present some natural frequency selectivity. The web and void design of the individual blocks and their arrangement within a building wall/interface, creates a periodic structure, which exhibits frequency dependent transmission and reflection characteristics. This behaviour as well as the scattering behaviour of conventional periodic building structures have been studied through the RCWA method. However, since the internal structure and the parameters of the building interfaces are usually unknown, it is not currently very practical to utilise this natural frequency selectivity. This may change if an easy way is found to "x-ray" the wall. Therefore, the novel way proposed, is to artificially transform the building interfaces into frequency selective ones, tuneable at a desired frequency through the deployment of Frequency Selective Surfaces (FSS). FSS are planar periodic structures consisting of identical thin conducting elements, usually printed on dielectric substrates. They behave as spatial electromagnetic filters selectively reflecting or attenuating a desired frequency band. Investigation was focused on studying through CFDTD simulations and anechoic chamber measurements the behaviour of FSS when these are attached on conventional building materials. It was found that beyond a certain distance (one tenth of the wavelength) away from the wall, the frequency response of the FSS remains unchanged. The potential benefits in signal coverage, interference reduction and capacity increase through a MIMO system have been studied through a custom written Hybrid Ray Tracing model, which incorporates the behaviour of frequency selective surfaces. It is to the author best knowledge that such a hybrid Ray Tracing model has never been proposed in open literature.
14
Karderinis, Sideris. "Spectroscopic studies of radio-frequency plasmas." Thesis, University of Oxford, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.325952.
15
Valenta, Václav. "Frequency synthesis for cognitive multi-radio." Phd thesis, Université Paris-Est, 2010. http://tel.archives-ouvertes.fr/tel-00597461.
Abstract:
This doctoral thesis deals with design aspects of a reconfigurable frequency synthesizer for flexible radio transceivers in future cognitive multi-radios. The frequency bandwidth to be covered by this multi-radio synthesizer corresponds to the frequency bands of the most diffused wireless communication standards in the frequency band 800 MHz to 6 GHz. Since multi-standard operation is required, the synthesizer must fulfil the most stringent and sometimes conflicting requirements. Given these requirements, a novel approach for multi-mode frequency synthesis has been conceived. A hybrid phase locked loop based frequency synthesizer has been proposed and a novel switching protocol has been presented and validated on an experimental evaluation board. This approach combines fractional-N and integer-N modes of operation with switched loop filter topology. Compared to standard PLL techniques, the hybrid configuration provides a great flexibility in terms of reconfiguration and moreover, it offers relatively low circuit complexity and low power consumption. This architecture provides reconfiguration of the loop bandwidth, frequency resolution, phase noise and settling time performance and hence, it can adapt itself to diverse requirements given by the concerned wireless communication standards. Corresponding analyses, simulations and measurements have been carried out in order to verify the performance and functionality of the proposed solution. A part from the design of the multiband frequency synthesizer, a set of regional measurements of the radio spectrum utilization has been carried out in the framework of this dissertation research. These measurements are based on the energy detection principle and provide a close look at the degree of radio spectrum utilization in different regions, namely in the city of Brno in the Czech Republic and in the city of Paris and one of its suburbs in France. The goal of the experimental measurement campaign has been to estimate the degree of radio spectrum usage in a particular environment and to point out the fact that a new approach for radio spectrum management is inevitable
16
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.
17
Madic, Jelena 1977. "Security Sphere : radio frequency subsampling receiver." Thesis, Massachusetts Institute of Technology, 2001. http://hdl.handle.net/1721.1/87251.
Abstract:
Thesis (M.Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, June 2002.Includes bibliographical references (p. 85-86).
by Jelena Madic.
M.Eng.
18
Rivas, Juan 1976. "Radio frequency dc-dc power conversion." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/38691.
Abstract:
Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, February 2007.Includes bibliographical references (p. 197-204).
THIS THESIS addresses the development of system architectures and circuit topologies for dc-dc power conversion at very high frequencies. The systems architectures that are developed are structured to overcome limitations associated with conventional designs. In particular, the new architectures described here structure the energy processing and control functions of the system in such a manner that high efficiency can be achieved across wide load range while regulating the output. Moreover, these architectures are amenable to circuit designs operating at fixed frequency and duty ratio, considerable easing the circuit design. The thesis also develops new circuit designs that are well suited to these new architectures. As part of this, two new gate drives and control methods are introduced that greatly reduce gating loss at VHF frequencies for fixed frequency, fixed duty ratio operation. One of these gating schemes provides near theoretical minimum loss by resonantly wave shaping the gate voltage to have a trapezoidal drive voltage. This waveshaping approach is then taken a step further, yielding a new class of dc-dc converter that archives a significant reduction in peak switch voltage stress, requires small passive components with low energy storage, and provides the capability for extremely rapid startup and shutdown. This new class of converter is well adapted to the architectures and gate drive methods proposed in the thesis. It is expected that the new architectures and circuit designs introduced here will contribute to the development of power converter having greatly reduced size and improved transient performance.
by Juan Rivas.
Sc.D.
19
Luschas, Susan 1975. "Radio frequency digital to analog converter." Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/28277.
Abstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2003.Includes bibliographical references (p. 124-126).
Dynamic performance of high speed, high resolution digital-to-analog converters (DACs) is limited by distortion at the data switching instants. Inter-symbol interference (ISI), imperfect timing synchronization and clock jitter are all culprits. A DAC output current controlled by an oscillating waveform is proposed to mitigate the effects of the switching distortion. The oscillating waveform should be a multiple (k*fs) of the sampling frequency (f), where k>l. The waveforms can be aligned so that the data switching occurs in the zero regions of the oscillating output. This makes the DAC insensitive to switch dynamics and jitter. The architecture has the additional benefit of mixing the DAC impulse response energy to a higher frequency. An image of a low IF input signal can therefore be output directly at a high IF or RF frequency for transmit communications applications. A narrow-band sigma-delta DAC with eight unit elements is chosen to demonstrate the radio frequency digital-to-analog converter (RF DAC) concept. A sigma-delta architecture allows the current source transistors to be smaller since mismatch shaping is employed. Smaller current source transistors have a lower drain capacitance, allowing large high frequency output impedance to be achieved without an extra cascode transistor. Elimination of the cascode reduces transistor headroom requirements and allows the DAC to be built with a 1.8V supply. The RF DAC prototype is targeted to GSM transmit specifications and implemented in 0.1 8ptm CMOS technology. Measured single-tone SFDR is -75dBc, SNR is 52dB, and IMD3 is -70.8dBc over a 17.5MHz bandwidth centered at 942.5MHz. Measured SNR has the predicted dependence on the phase alignment of the data clock and oscillating pulse.
by Susan Luschas.
Ph.D.
20
Mohd, Yusof Yuslinda. "Miniature magneto-inductive radio frequency sensors." Thesis, University of Cambridge, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.615702.
21
Neophytou, Regas Ioanni. "Modelling of radio frequency heating systems." Thesis, University of Cambridge, 1998. https://www.repository.cam.ac.uk/handle/1810/272305.
22
Sihlangu, Isaac. "The MeerKAT Radio Frequency Interference Environment." Master's thesis, Faculty of Science, 2019. https://hdl.handle.net/11427/31748.
Abstract:
Radio signals from astronomical sources are extremely weak and easily distorted/- corrupted or overwhelmed by man-made radio signals such as cellphones, satellites, aircraft and telescope electronics. These Radio Frequency Interference (RFI) are increasingly threatening radio observatories due to our increasingly technological world. To detect and mitigate RFI, observatories need to understand their RFI environment, what contributes to it and how it is changing. While there are few dedicated RFI monitoring systems on the MeerKAT site, the most sensitive RFI detector is the MeerKAT array itself. In this thesis we use approximately 1500 hours of MeerKAT observations to create a multi-dimensional view of the RFI at the MeerKAT site. Here we investigate a probabilistic approach to characterise the RFI environment around the MeerKAT radio telescope. In order to achieve our goal, we propose the MeerKAT Historical Probability of RFI (KATHPRFI) framework. We produced the high level requirements of the KATHPRFI framework driven by the needs of the MeerKAT users. The design approach and the design decision of the framework is presented that cover both the software and hardware constraints. The KATHPRFI produces a 5-dimensional array of the RFI probability as measured by the MeerKAT telescope during the commissioning phase (May 2018 - December 2018) for each observation file. From the 5-D array, we extracted various statistics and characterised the RFI environment around MeerKAT site. We found that there is a correlation between RFI occupancy and the time of the day which is most probably related to human activities. Furthermore, we found a correlation between the time of the day and flights passing over a region of site. Our results showed that the highest probability of RFI points towards a region including nearby towns. The results obtained are consistent with the argument that the major RFI sources for MeerKAT site are the Global Positioning System (GPS) satellite, flight Distance Measurement Equipment (DME) and the Global System for Mobile Communications (GSM). Our data also showed that the RFI occupancy decreases with an increase of baseline length, this is a result of moving RFI sources with respect to the static sky. Therefore, the phase of the RFI changes rapidly on long baselines compared to short baselines. As a result when a correlation is carried out the RFI amplitude will vanish less on short baselines compared to the long baselines. Our results provide the first highly detailed view of the MeerKAT RFI environment allowing us to track the historical evolution of the RFI, both on average, and as a function of frequency, baseline and direction. With historical baselines known, one can also provide alerts about sudden changes. This could be due to new sources of RFI or stem from any outliers in the data, which could signal telescope or correlator issues. Hence the KATHPRFI framework also provides a window into the operational health of the telescope.
23
Jagoo, Mohammud Zafrullah. "Radio-frequency Heating of Magnetic Nanoparticles." Wright State University / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=wright1334849224.
24
Venkatesh, Prabhu. "Radio frequency-based data collection network." Master's thesis, This resource online, 1995. http://scholar.lib.vt.edu/theses/available/etd-01262010-020232/.
25
Mirowski, L. "Detecting Clone Radio Frequency Identification Tags." Thesis, Honours thesis, University of Tasmania, 2006. https://eprints.utas.edu.au/792/1/Detecting_Clone_Radio_Frequency_Identification_Tags.pdf.
Abstract:
The theft of Radio Frequency Identification (RFID) tag identity, commonly referred to as tag cloning, is a serious threat to RFID systems. It can enable an attacker to gain access to a secure facility, make fraudulent purchases, or disrupt supply chains. It may even enable crimes like financial gain, people smuggling, and drug trafficking, terrorism and money laundering. Presently there is no practical solution to defend against tag cloning. This thesis details research that aims to detect the presence of clone tags which may be the first step in defending against them and preventing RFID-enabled crimes from occurring. An intrusion detection system has been developed using statistical anomaly detection to identify clone tags. The feasibility of the approach has been tested by evaluating its performance in detecting synthesized attacks inside a sanitized RFID audit log. The results suggest that intrusion detection systems can be used to detect cloned tags but that the weaknesses of statistical anomaly detection are also apparent when used on RFID data.
26
Murji, Rizwan Deen M. Jamal. "Low-power CMOS radio frequency integrated circuits for frequency synthesis /." *McMaster only, 2005.
27
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/.
28
Atefi, A. "An investigation of radio wave propagation in mobile radio frequency bands." Thesis, University of Liverpool, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.354537.
29
Kim, Hyung Joon. "Multi-standard radio transceiver architectures and radio frequency front-end design." Connect to this title online, 2005. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1110399471.
Abstract:
Thesis (Ph. D.)--Ohio State University, 2005.Title from first page of PDF file. Document formatted into pages; contains xv, 128 p.; also includes graphics (some col.). Includes bibliographical references (p. 125-128). Available online via OhioLINK's ETD Center
30
Appler, Jason A. Finney Sean M. McMellon Michael A. "Aerial remote radio frequency identification system for small vessel monitoring." Monterey, California : Naval Postgraduate School, 2009. http://edocs.nps.edu/npspubs/scholarly/MBAPR/2009/Dec/09Dec%5FAppler%5FMBA.pdf.
Abstract:
"Submitted in partial fulfillment of the requirements for the degree of Master of Business Administration from the Naval Postgraduate School, December 2009."Advisor(s): Dew, Nicholas ; Hudgens, Bryan. "December 2009." "MBA Professional report"--Cover. Description based on title screen as viewed on January 26, 2010. Author(s) subject terms: RFID, Radio Frequency Identification, airborne, vessel monitoring. Includes bibliographical references (p. 103-110). Also available in print.
31
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.
32
Wiles, Andrew Donald. "Modelling Framework for Radio Frequency Spatial Measurement." Thesis, University of Waterloo, 2006. http://hdl.handle.net/10012/771.
Abstract:
The main crux of this thesis was to produce a model that was capable of simulating the theoretical performance of different configurations for a spatial measurement system using radio frequency technology. It has been important to study new modalities of spatial measurement since spatial measurement systems are an enabling technology that have allowed for the creation of better medical procedures and techniques, provided valuable data for motion capture in animation and biomechanics, and have improved the quality of manufacturing processes in many industries. However, there has been room for improvement in the functional design and accuracy of spatial measurement systems that will enhance current applications and further develop new applications in medicine, research and industry. In this thesis, a modelling framework for the investigation of spatial measurement based on radio frequency signals was developed. The simulation framework was designed for the purpose of investigating different position determination algorithms and sensor geomatries. A finite element model using the FEMLAB partial differential equation modelling tool was created for a time-domain model of electromagnetic wave propagation in order to simulate the radio frequency signals travelling from a transmitting source antenna to a set of receiving antenna sensors. Electronic line signals were obtained using a simple receiving infinitesimal dipole model and input into a time difference of arrival localization algorithm. The finite element model results were validated against a set of analytical solutions for the free space case. The accuracy of the localization algorithm was measured against a set of possible applications for a potential radio frequency spatial measurement system design.
It was concluded that the simulation framework was successful should one significant deficiency be corrected in future research endeavours. A phase error was observed in the signals extracted at the receiving antenna locations. This phase error, which can be up to 40°, was attributed to the zeroth order finite elements implemented in the finite element model. This phase error can be corrected in the future if higher order vector elements are introduced into future versions of FEMLAB or via the development of custom finite element analysis software but were not implemented in this thesis due to time constraints. Other improvements were also suggested for future work.
33
Alexander, Paul. "Multi-frequency studies of powerful radio sources." Thesis, University of Cambridge, 1986. https://www.repository.cam.ac.uk/handle/1810/265339.
Abstract:
This thesis is concerned with the physics of extragalactic radio - sources. Radio observations of a given source provide a powerful method with which to make direct measurements of the physical processes occuring within the la~ge-scale radio lobes and hotspots . Multi-frequency observations with up to five frequencies have been made for a number of ~ources using the Cambridge 5-km telescope and the Very Large Array. These data have been used to determine the change in radio spectra across the source . to obtain information about the way in which the electron population has evolved. Combining this with inferred magnetic field directions, the dynamics of seven sources have been examined. Additionally the hotspot advance speeds for a statistically representative sample of sources have -been derived. For 3C234 it was possible to test the assumptions used throughout the analysis. They were found to h6ld good to within the limits of error. The results are best interpreted within the framework of a fluid-dynamical model lobes as have recently been examined in numerical experiments. The general distibution of radiating plasma can be understood in terms of the flow of material out of the main accelerating regions (the hotspots - a basic beam model � is assumed thr6ughout) and its subsequent interaction with the surrounding medium, coupled with some precession of the radio jet. As well as looking at source dynamics , the detailed spectra have been used to search for areas of particle acceleration not associated with hotspots. Three sources have been found to have such regions, but large scale acceleration within the radio-lobes is not required . The derivation of ho tspot advance speed for a statistically representative sample has enabled statistical correlations to be investigated . Advance speed is found to be strongly correlated with power and this is discussed in the wider context of overall source models.
34
Rockliff, Simon C. "Frequency hopping techniques for digital mobile radio /." Title page, contents and abstract only, 1990. http://web4.library.adelaide.edu.au/theses/09PH/09phr683.pdf.
35
Chen, Xi. "Sequential Monte Carlo radio-frequency tomographic tracking." Thesis, McGill University, 2011. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=104844.
Abstract:
Target tracking in over a small-scale area using wireless sensor networks (WSNs) is a technique that can be used in applications ranging from emergency rescue after an earthquake to security protection in a building. Many target tracking systems rely on the presence of an electric device which must be carried by the target in order to reports back its location and status. This makes these systems unsuitable for many emergency applications; in such applications device-free tracking systems that where no devices are attached to the targets are needed. Radio-Frequency (RF) tomographic tracking is one such device-free tracking technique. This system tracks moving targets by analyzing changes in attenuation in wireless transmissions. The target can be tracked within the sensor network area without being required to carry an electric device.Some previously-proposed device-free tracking approaches require a time-consuming training phase before tracking can be carried out, which is time-consuming. Others perform tracking by sacrificing part of the estimation accuracy. In this thesis, we propose a novel sequential Monte Carlo (SMC) algorithm for RF tomographic tracking. It can track a single target moving in a wireless sensor network without the system needing to be trained. The algorithm adopts a particle filtering method to estimate the target position and incorporates on-line Expectation Maximization (EM) to estimate model parameters. Based on experimental measurements, the work also introduces a novel measurement model for the attenuation caused by a target with the goal of improving estimation accuracy. The performance of the algorithm is assessed through numerical simulations and field experiments carried out with a wireless sensor network testbed. Both simulated and experimental results demonstrate that our work outperforms previous RF tomographic tracking approaches for single target tracking.Suivi de cible dans la zone à petite échelle en utilisant les réseaux de capteurs sans fil est une technique qui peut être largement utilisé dans des applications telles que le sauvetage d'urgence après un tremblement de terre, ou la protection de la sécurité dans un bâtiment. Beaucoup de systèmes de poursuite de cibles nécessitent un dispositif électrique réalisée par l'objectif de faire rapport de ses localisation instantanée et le statut. L'inconvénient rend ces systèmes ne conviennent pas pour des applications nombreuses interventions d'urgence, dispositif sans systèmes de suivi qui ne les périphériques connectés sur les objectifs sont nécessaires. Radio-Fréquence (RF) suivi tomographique est l'une des techniques dispositif de suivi-libres. Il s'agit d'un processus de suivi des cibles mobiles en analysant l'évolution de l'atténuation dans les transmissions sans fil. La cible peut être suivi dans la zone de réseau de capteurs, tandis que les appareils électriques ne doivent être effectués. Cependant, certaines approches précédentes dispositif de suivi-libre nécessite une phase d'entraînement avant de suivi, ce qui prend beaucoup de temps. Autres effectuer un suivi par scarification partie de précision de l'estimation.Dans cette thèse, nous proposons une nouvelle Monte Carlo séquentielles (SMC) algorithme de suivi RF tomographique. Il peut suivre une cible unique sans formation du système dans un réseau de capteurs sans fil. L'algorithme de filtrage particulaire adopte la méthode pour estimer la position cible et intègre en ligne Expectation Maximization (EM) pour estimer les paramètres du modèle. Sur la base de mesures expérimentales, le travail introduit également un modèle de mesure de roman pour l'atténuation provoquée par une cible pour améliorer la précision d'estimation. La performance de l'algorithme est évaluée par des simulations numériques et expériences sur le terrain avec un réseau de capteurs sans fil banc d'essai. Les deux résultats simulés et expérimentaux démontrent que notre travail surpasse précédente approche RF suivi tomographique pour le suivi de cible unique.
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Davis, Stephen. "Radio frequency tagging in the retail industry." Thesis, University of the West of England, Bristol, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.262824.
37
Laufer, Deanna (Deanna Raquel). "Radio Frequency Identification : regulating information privacy protection." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/41767.
Abstract:
Thesis (S.M.)--Massachusetts Institute of Technology, Engineering Systems Division, Technology and Policy Program, 2007.Includes bibliographical references (p. 82-87).
As applications of Radio Frequency Identification (RFID) become more profuse, the technology itself is stirring up some controversy. Due to its potential for amassing large amounts of information about both people and things, and the possibility of using the information for marketing, tracking, or even spying, numerous consumer groups are spearheading efforts to ensure that RFID does not breach their privacy rights. While there are some privacy laws regulating specific aspects of commerce, there are no laws which currently apply to the collection and use of information as it pertains to RFID. This lack of formal regulation allows companies to legally engage in practices which may encroach on consumers' privacy. However, RFID has the potential to optimize supply chain practices as well as provide other benefits to both consumers and businesses. As RFID use becomes more widespread, regulatory strategies should be considered to protect consumers' right to privacy while obtaining the benefits of using the technology. This thesis explores consumer and industry opinion of RFID through a customized survey. Results of the survey found that consumer and industry opinion are similar in many aspects, especially in the concern for protecting privacy and the desire for a regulatory mechanism to enforce those privacy rights. This thesis addresses the question of whether market-based solutions, self-regulation, or government regulation is the best option for addressing consumers' legitimate concerns of privacy while allowing businesses to reap the benefits of using the technology.
(cont.) The regulatory options are compared and then discussed based on the needs of consumers and industry members as determined by the survey. Finally, four recommendations are suggested to provide guidance for ensuring a positive acceptance of RFID while acknowledging the privacy rights of consumers.
by Deanna R. Laufer.
S.M.
38
Forbess, Jessica (Jessica Anne) 1975. "Medium frequency radio propagation in urban settings." Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/86471.
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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.
Abstract:
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.
40
Nation, Joshua C. (Joshua Caleb). "Fabrication of chip-scale radio frequency inductors." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/92067.
Abstract:
Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2014.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 101-104).
The purpose of this research was to learn the relationship between force and deformation in forming of micro-scale inductor coils. This was accomplished by applying large-deflection beam bending to the case of planar wire deformation and through experimental validation. Generating this knowledge is important because it establishes fabrication limits for wire-based chip-scale inductors. There are many potentially viable methods for fabricating planar inductor coils. Without an understanding of the relevant physics, it is impossible to know which of these techniques is most appropriate or even feasible. The analysis presented in this thesis directly led to the stencil-and-guide inductor fabrication concept, the details of which were specified using an analytic electrical model. The process utilizes a wire conductor, is compatible with any desired substrate, and features the ability to exactly control spiral properties. Multiple inductors were fabricated using this process. These inductors demonstrate performance specifications predicted by the model, including inductances ranging from 2 - 4 nH, quality factors in excess of 100, and self-resonant frequencies beyond 10 GHz. Furthermore, the area of the inductors is less than 1.5 mm2 and the entire device thickness is only 260 [mu]m. The inductors are most readily applied to increasingly small communication devices, which require thin and efficient electrical components to boost the performance of the radio frequency transceiver. Accordingly, these inductors offer the potential for substantial improvement in signal quality and reception.
by Joshua C. Nation.
S.M.
41
Foley, Joseph Timothy 1976. "Security approaches for Radio Frequency Identification systems." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/38710.
Abstract:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2007.Includes bibliographical references (p. 253-270) and index.
In this thesis, I explore the challenges related to the security of the Electronic Product Code (EPC) class of Radio Frequency Identification (RFID) tags and associated data. RFID systems can be used to improve supply chain performance and automate asset management. However, an antagonist could use the functionality of the RFID tags and the EPC data to invade personal privacy or acquire access to unauthorized corporate information such as inventory levels. In addition, current RFID mechanisms expose secrets to the readers, which opens an avenue for exploits and information leakage. I examined the RFID security and privacy issues and designed a number of systems to improve tag authentication, privacy protection, and secure sharing of EPC data. The specific solutions I propose include TagCheck to protect tags from counterfeiting, JanusTag to allow recoverable dynamic recoding of tags, TagFolio for privacy policy enforcement, and TagDirective for secret management and access control. To prevent leakage at the application level during Object Name System (ONS) resolution, I propose the use of an anonymizing TorONS system.
(cont.) Lastly, to protect tags from being "mass killed", I designed two different categories of RFID tag kill-resistance mechanisms: active protection using Neighborhood Watch communities of readers and Exponential Rampup for tag self-defense. These technologies are combined under one umbrella called TinFoil, creating a comprehensive security solution that successfully protects the data in an EPC-enabled RFID system while minimizing required modifications to existing architecture.
by Joseph Timothy Foley.
S.M.
42
Liney, David John. "Radio frequency properties of high Tc superconductors." Thesis, University of Cambridge, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.624839.
43
Gurr, J. Richard, Anthony Auvil, and Jim Rizzo. "WIDE-BAND RADIO FREQUENCY (RF) SOURCE SURVEILLANCE." International Foundation for Telemetering, 1998. http://hdl.handle.net/10150/607394.
Abstract:
International Telemetering Conference Proceedings / October 26-29, 1998 / Town & Country Resort Hotel and Convention Center, San Diego, CaliforniaReduction in available radio frequency (RF) spectrum for use in aircraft testing has steadily increased the probability of interference. The increase in users and required bandwidth generates requirements for increased monitoring and active management of the RF spectrum. The detection of background RF emissions and monitoring of authorized users will be used by future range test engineers to make decisions on when and where to conduct test missions to minimize the probability of interference. The detection of authorized users exceeding their allotted RF spectrum as well as unknown emitters should include: the general geographic area of potential interference, and times of transmission. This paper outlines the development of a complete system for wide-band RF monitoring to identify and locate active emissions. The RF surveillance system proposed must be inexpensive, easy to maintain, support large area coverage, and monitor wide bandwidths at long range. The system should contain software for emitter identification, which will determine where the current background and authorized RF transmissions occur and how they might effect authorized transmissions, and specialized software to alert spectrum managers of potential interference scenarios in real time based upon the daily schedule.
44
Tegkelidis, Christos, and Erik Lindström. "Modeling of Radio Frequency Heating in JET." Thesis, KTH, Skolan för elektroteknik och datavetenskap (EECS), 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-293886.
Abstract:
This study examines the efficiency of ion cyclotronresonance heating in multi-ion plasmas in JET (Joint EuropeanTorus), using deuterium and tritium as fuel along with smallconcentrations of a third ion species. In particular, two ionminority scenarios, hydrogen and helium, as well as a 3-ionscenario using beryllium were constructed. The scenarios weresimulated with FEMIC and the obtained data was then compiledand analyzed through a number of metrics.The highest total power absorption was 8.56 W and wasachieved by the 4% hydrogen scenario. However, 8% hydrogenattained the highest power partition by the minority ion species.The optimal beryllium concentration regarding absorbed powerwas 0.1% in 36.2% deuterium and 63.4% tritium, with a totalcoupled power of 6.94 W. The highest power partition byberyllium was noted for the 0.25% case in a 36% deuteriumand 63% tritium plasma.Denna studie undersöker effektiviteten av joncyklotronresonansuppvärmning av JETs (Joint European Torus) plasma, med deuterium och tritium som bränsle, samt små koncentrationer av ett tredje ämne. Mer specifikt undersöks två scenarier med minoritetsjoner, helium och väte, och ett 3-jonscenario med beryllium. För att undersöka dessa olika konstellationer körs simuleringar i FEMIC. Datan som fås från simuleringarna sammanställs och analyseras i enlighet med olika mått. Den högsta totala absorptionen av energi var 8.56 W och fas av 4% väteminoritet. 8% väte ger den högsta energipartitionen för det tredje jonslaget. Beryllium absorberade som mest 6.94 W, detta med 0.1% beryllium, 36.2% deuterium och 63.4% tritium. Den högsta energipartitionen för beryllium uppnåddes med 0.25% beryllium, 36% deuterium och 63% tritium.
Kandidatexjobb i elektroteknik 2020, KTH, Stockholm
45
ABASCAL, CARLOS G. "ADAPTIVE EQUALIZATION OF A RADIO FREQUENCY AMPLIFIER." University of Cincinnati / OhioLINK, 2001. http://rave.ohiolink.edu/etdc/view?acc_num=ucin983391684.
46
Pan, Kuan-Chang. "Vanadium Dioxide Based Radio Frequency Tunable Devices." University of Dayton / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=dayton154341840843132.
47
Harrison, Kyle. "Machine Learning for Radio Frequency Interference Flagging." Master's thesis, Faculty of Engineering and the Built Environment, 2021. http://hdl.handle.net/11427/33777.
Abstract:
The field of radio frequency interference (RFI) flagging involves the identification of corrupted data within radio astronomy measurements. This work explores the application of supervised machine learning algorithms for RFI flagging, trained on real measurement data and simulated data with simulated RFI. The goal of this work is to investigate the prediction of RFI using specific machine learning algorithms; Naive Bayes Classifier, K-Nearest Neighbours Classifier, Random Forest Classifier, the U-Net convolution neural network and the Multilayer Perceptron. These algorithms are trained on real data, in which the ground truth includes inherent false positives, and simulated data where the ground truth positions of RFI are absolute. This is done through the use of time/frequency spectrogram data, relating to radio astronomy measurements, using the magnitudes and phases of each available polarization. Predictions for unseen test data are compared between algorithms, different implementations of those algorithms and each dataset. A specific implementation for data pre-processing is designed and implemented, utilizing a two dimensional filtering technique for feature construction. The goal of this method is intended to implement a means of injecting a form of spatial information of nearby time/frequency samples for each sample in a spectrogram. The inclusion of this spacial information, which is relevant to broadband bursts and narrowband persistent RFI, is hypothesised to increase the level of information present in the processed dataset. The use of feature construction using filtering techniques, demonstrates a noticeable improvement in the machine learning methods where each sample is treated individually during training and inference.
48
Sivarajan, Kumar N. McEliece Robert J. McEliece Robert J. "Spectrum efficient frequency assignment for cellular radio /." Diss., Pasadena, Calif. : California Institute of Technology, 1990. http://resolver.caltech.edu/CaltechETD:etd-11082007-105043.
49
Kim, David Storm. "Hybrid free-space and radio frequency switching." College Park, Md.: University of Maryland, 2008. http://hdl.handle.net/1903/8913.
Abstract:
Thesis (M.S.) -- University of Maryland, College Park, 2008.Thesis research directed by: Dept. of Electrical and Computer Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
50
Liu, Xiaojian. "Radio frequency evaluation of oriented strand board." Diss., Mississippi State : Mississippi State University, 2008. http://library.msstate.edu/etd/show.asp?etd=etd-07082008-145942.