Дисертації з теми "Microwave radio"
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1
Zhang, Guoyong. "Superconducting microwave components for radio astronomy applications." Thesis, University of Birmingham, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.435303.
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2
Russell, Thomas A. "Predicting microwave diffraction in the shadows of buildings." Thesis, This resource online, 1991. http://scholar.lib.vt.edu/theses/available/etd-10222009-125156/.
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3
Jordan, Jennifer L. "Contactless Radio Frequency Probes for High Temperature Characterization of Microwave Integrated Circuits." Case Western Reserve University School of Graduate Studies / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=case1402066531.
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4
Özcan, Sibel. "Radio frequency and microwave properties of unconventional superconductors." Thesis, University of Cambridge, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.619555.
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Young, Michael C. S. "Application of adaptive equalisation to microwave digital radio." Thesis, University of Edinburgh, 1989. http://hdl.handle.net/1842/11654.
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6
Banciu, Marian Gabriel Electrical Engineering & Telecommunications Faculty of Engineering UNSW. "Radio frequency and microwave design methods for mobile communications." Awarded by:University of New South Wales. School of Electrical Engineering and Telecommunications, 2003. http://handle.unsw.edu.au/1959.4/18814.
Повний текст джерелаАнотація:
The Global System for Mobile communications (GSM), which covers 54% of the world's mobile market, evolved into the General Packet Radio Service (GPRS). The thesis addresses interference suppression using new radio frequency (RF) and microwave design methods for GSM and GPRS. The overall outcome is interference reduction and enhanced network capacity, leading to superior quality of service (QoS) for wider area coverage. The main results can be summarized as follows * Design, manufacturing and characterisation measurements of new compact filters for GSM and GPRS base stations in order to reduce the out-of-band interference. It is shown that filters with novel microstrip resonators - dual mode filters and cross coupled filters - provide both a high degree of miniaturisation and narrow bandwidth. * Development of a new 3-D Finite-Difference Time-Domain (FDTD) design method for new microstrip filters. A non-homogeneous Perfectly Matched Layer (NH-PML) was implemented for Absorbing Boundary Conditions (ABC) to increase the accuracy of the FDTD method. Signal estimation techniques were developed to speed up FDTD computations. A novel design method based on neural networks (NN) and FDTD was implemented to reduce the total design time. * Investigation of High Temperature Superconductors (HTS) thin film resonators and antennas at microwave frequencies. High Q-factor HTS devices considerably enhance both the front-ends sensitivity and selectivity of wireless receivers. * Design, manufacturing and testing of radio frequency (RF) electronics for 16 elements GSM and GPRS Smart Antenna for multipath fading mitigation and for in-band interference including co-channel interference (CCI) suppression.
7
Nader, Joe. "Modeling and performance of microwave radio links in rain." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0022/MQ50644.pdf.
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Nader, Joe. "Modeling and performance of microwave radio links in rain." Thesis, McGill University, 1998. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=21315.
Повний текст джерелаАнотація:
Microwave radio links, operating in the millimeter wave region, must account for the effects of rain when considering transmission loss. In this work, a theoretical model is used to generate the specific attenuations based on perturbation theory with spheroidal or Pruppacher-Pitter raindrop shapes, and Marshall-Palmer or Weibull drop size distributions. The specific attenuation is fitted to the power law relation with rain rate and the parameters are used in a two-component rain rate model in order to estimate the attenuation along the path.The theoretical model is simulated and compared to the ITU and Crane prediction methods. Both moderate and tropical climates are considered. A simple line-of-sight radio system is then simulated and evaluated by incorporating the rain attenuation in the channel. Finally, three basic network blocks are discussed and analyzed for links affected by rain.
9
NAVARRO, KEYLA MARIA MORA. "RAIN EFFECTS ON MICROWAVE AND MILLIMETER WAVE RADIO LINKS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2017. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=33982@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROCOORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO
PROGRAMA DE EXCELENCIA ACADEMICA
A principal meta desta tese é estudar os efeitos da chuva nos enlaces operando na faixa de micro-ondas e comprimentos de ondas milimétricas. Para realizar este estudo, é considerado o modelo de chuva que considera um meio de chuva realista composto por um conjunto de gotas com a relação formato-tamanho proposta por Chuang e Beard, uma distribuição de tamanho das gotas dada por de Wolf, o índice de refração complexo da água para uma frequência e temperatura dada sugerido por Ray e uma distribuição de orientação dos eixos de simetria da partícula. O Extended Boundary Condition Method (EBCM) foi aplicado ao modelo descrito para determinar a atenuação, depolarização e espalhamento devidos à chuva. O desenvolvimento foi validado com sucesso por intermédio de comparações de seus resultados com os correspondentes disponíveis na literatura. O modelo de chuva realista foi utilizado em duas aplicações diferentes. Na primeira, foi estudada a interferência devida à chuva entre enlaces de telecomunicações sem fio operando em frequências de ondas milimétricas em ambientes urbanos. Outra aplicação envolve a determinação da taxa de precipitação por intermédio de radares meteorológicos (em particular, radares banda-X). Considerando que seu custo é relativamente baixo e sua resolução elevada, os radares em banda-X estariam entre as melhores opções para monitorar eventos meteorológicos. Entretanto, são susceptíveis à atenuação devida a gases atmosféricos e chuva ao longo dos enlaces, que impedem que a taxa de precipitação seja estimada diretamente a partir da potência recebida correspondente a uma determinada posição. Desta forma, um modelo de chuva realista foi implementado para calcular a seção reta de retroespalhamento e estimar a atenuação específica por intermédio do EBCM em cada um dos volumes existentes entre o radar e a posição selecionada. Este desenvolvimento permite a correção dos efeitos da atenuação existente no enlace formado entre estas duas posições.
The main goal of this research is to study the rain effects on microwave and millimeter wave radio links. Thus, the rain-induced attenuation, depolarization and scattering are studied. To carry out this study, a realistic rain model is proposed, which consider a realistic rain medium composed by a cluster of raindrops with the shape-size relation proposed by Chuang and Beard, a raindrop size distribution given by de Wolf, index of refraction of water for a given temperature and frequency suggested by Ray and a distribution of the orientation angle of the symmetry axis. The realistic rain model is evaluated with two different applications of systems operating at microwave and millimeter wave frequencies. One of the applications involves wireless telecommunication systems, which are strongly affected by the presence of precipitation. To design an efficient radio communication system, the realistic rain model is applied for the analysis and quantification of rain-induced effects on links operating at millimeterwave frequencies in urban environments. Another application involves weather radars (X-band radars in particular). Considering their relatively low cost and high resolution, X-band radars would be among the best options to monitor meteorological events. However, they are susceptible to attenuation by fog, snow or rain. To solve this problem, a realistic and improved rain model is implemented to compute backscattering cross sections and estimate rain attenuation at each range gate. The proposed method is evaluated using radar data provided by the CASA OTG X-band (lambda equal a 3cm) radar located in Mayaguez, Puerto Rico, and X-band radar METEOR 50DX –Selex located in Belém, Brazil.
10
Ijaha, Stephen Ejeh. "Performance characterization of long-distance digital microwave radio systems." Thesis, Imperial College London, 1988. http://hdl.handle.net/10044/1/47120.
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Spillard, Candida. "Transhorizon microwave propagation and its relationship with meteorological conditions." Thesis, University of Portsmouth, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.277199.
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12
Rodríguez, Gonzálvez Carmen. "Analysis of cosmic microwave background observations with the Arcminute Microkelvin Imager." Thesis, University of Cambridge, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.609911.
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13
Kincaid, Cheryl-Annette Mikler Armin. "Analyzing microwave spectra collected by the solar radio burst locator." [Denton, Tex.] : University of North Texas, 2007. http://digital.library.unt.edu/permalink/meta-dc-3655.
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14
Guner, Baris. "Studies of Radio Frequency Interference Detection Methods in Microwave Radiometry." The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1238780286.
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Kincaid, Cheryl-Annette. "Analyzing Microwave Spectra Collected by the Solar Radio Burst Locator." Thesis, University of North Texas, 2007. https://digital.library.unt.edu/ark:/67531/metadc3655/.
Повний текст джерелаАнотація:
Modern communication systems rely heavily upon microwave, radio, and other electromagnetic frequency bands as a means of providing wireless communication links. Although convenient, wireless communication is susceptible to electromagnetic interference. Solar activity causes both direct interference through electromagnetic radiation as well as indirect interference caused by charged particles interacting with Earth's magnetic field. The Solar Radio Burst Locator (SRBL) is a United States Air Force radio telescope designed to detect and locate solar microwave bursts as they occur on the Sun. By analyzing these events, the Air Force hopes to gain a better understanding of the root causes of solar interference and improve interference forecasts. This thesis presents methods of searching and analyzing events found in the previously unstudied SRBL data archive. A new web-based application aids in the searching and visualization of the data. Comparative analysis is performed amongst data collected by SRBL and several other instruments. This thesis also analyzes events across the time, intensity, and frequency domains. These analysis methods can be used to aid in the detection and understanding of solar events so as to provide improved forecasts of solar-induced electromagnetic interference.
16
Vidal, Navarro Matias Ambrosio. "Diffuse radio foregrounds : all-sky polarisation and anomalous microwave emission." Thesis, University of Manchester, 2014. https://www.research.manchester.ac.uk/portal/en/theses/diffuse-radio-foregrounds-allsky-polarisation-and-anomalous-microwave-emission(95da26a0-964b-4741-a25d-ba46dbeed590).html.
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In this Thesis, we present work on the diffuse Galactic emission in the 23−43 GHz frequency range. We studied the polarised emission, which is dominated by synchrotron radiation at these frequencies. We also present work on the anomalous microwave emission (AME), both in total intensity and polarisation. These observations are useful to quantify the CMB foreground contribution and give us information about the ISM of our Galaxy. Polarisation observations are affected by a positive bias, particularly important in regions with low signal-to-noise ratio. We present a method to correct the bias in the case where the uncertainties in the Q, U Stokes parameters are not symmetric. We show that this method successfully corrects the polarisation maps, with a residual bias smaller than the random uncertainties on the maps, outperforming the methods that are previously described in the literature. We use the de-biasing method to set upper limits for the polarisation of AME in the ρ Ophiuchi and Perseus molecular clouds. In both clouds the AME polarisation fraction is found to be less than 2% at 23 GHz and33 GHz. We use data from the WMAP satellite at 23, 33 and 41 GHz to study the diffuse polarised emission over the entire sky. This emission is due to synchrotron radiation and it originates mostly from filamentary structures with well-ordered magnetic fields. We identify new filaments and studied their observational properties, such as polarisation spectral indices, polarisation fraction and Faraday rotation. We explore the link between the large scale filaments and the local ISM, using the model of an expanding shell in the vicinity of the Sun. We also quantify the level of contamination added by the diffuse filaments to the CMB E- and B-mode power spectra. The Q/U Imaging ExperimenT (QUIET) observed the polarised sky at 43 and 95 GHz, in order to measure the CMB spectra. We describe the instrument, the observations and data processing, focusing on two regions of the Galactic plane. We study the foreground contamination in a region of the sky. We also discuss some properties of the diffuse synchrotron emission observed on the Galactic plane by QUIET. Using interferometric observations at 31 GHz, we studied AME in the translucent cloud LDN 1780. Interferometric data at 31 GHz and different ancillary data were used. We study the connection between the radio emission and the interstellar dust present in the cloud. The spinning dust hypothesis for the origin of AME is tested and we conclude that it can explain the radio properties observed in this cloud.
17
Lochtie, Gail D. "Propagation at microwave frequencies in the presence of tropospheric stratified layers." Thesis, University of Essex, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.303451.
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Weidt, Sebastian. "Towards microwave based ion trap quantum technology." Thesis, University of Sussex, 2014. http://sro.sussex.ac.uk/id/eprint/48893/.
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Scalability is a challenging yet key aspect required for large scale quantum computing and simulation using ions trapped in radio-frequency (rf) Paul traps. In this thesis 171Yb+ ions are used to demonstrate a magnetic field insensitive qubit which has a measured coherence time of 1.5 s, making it an ideal candidate to use for storing quantum information. A magnetic field sensitive qubit is also characterised which can be used for the implementation of multi-qubit gates using a potentially very scalable scheme based on microwaves in conjunction with a static magnetic field gradient instead of using lasers. However, the measured coherence time is limited by magnetic field fluctuations and will prohibit high fidelity gate operations from being performed. To address this issue, the preparation of a dressed-state qubit using a microwave based stimulated rapid adiabatic passage (STIRAP) pulse sequence will be presented. This qubit is protected against the noisy environment making it less sensitive to magnetic field fluctuations. The lifetime of this qubit is measured to demonstrate its suitability for storing quantum information. A powerful method for manipulating the dressed-state qubit will be presented and is used to measure a coherence time of the qubit of 500 ms which is two orders of magnitude longer compared to the magnetic field sensitive qubit. It will also be shown that our method allows for the implementation of arbitrary rotations of the dressed-state qubit on the Bloch sphere using only a single rf field. This substantially simplifies the experimental setup for single and multi-qubit gates. Furthermore, this thesis will present a experimental setup capable of successfully operating microfabricated surface ion traps. This setup is then used to operate and characterise the first two-dimensional (2D) lattice of ion traps on a microchip. A unique feature of the microfabrication technique used for this device is the extremely large voltage that can be applied which allows long ion lifetimes along with large secular frequencies to be measured, demonstrating the robustness of this device. Rudimentary shuttling between neighbouring lattice sites will be shown which could be used as part of a efficient scheme to load a large lattice of ions. One of the many applications of a 2D lattice of ions lies in the field of quantum simulations where many-body systems such as quantum magnetism, high temperature superconductivity, the fractional quantum hall effect and synthetic gauge fields can be simulated. It will be shown how making only minor modifications to the microchip the ion-ion separation can be reduced sufficiently to offer an exciting platform for the successful implementation of 2D quantum simulations. A theoretical investigation on the optimal 2D ion trap lattice geometry will also be presented with the aim to maximise the ratio of ion-ion coupling strength to decoherence from motional heating of the ions and to laser induced off-resonant coupling.
19
Trombino, Giuseppe. "Propagation performance of urban-path digital radio links operated at 6 and 38 GHz." Thesis, University of Ulster, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.288820.
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20
Aksoy, Mustafa. "Radio Frequency Interference Characterization and Detection in L-band Microwave Radiometry." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1448989873.
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21
Gale, David James. "An investigation into path analysis for line-of-sight microwave radio." Master's thesis, University of Cape Town, 1989. http://hdl.handle.net/11427/8333.
Повний текст джерелаАнотація:
Includes bibliography.An investigation into the analysis of Digital Microwave Radio Paths was conducted. The causes and effects of multipath fading on the propagation of microwave signals are of particular interest here. A study is made of the theory of link engineering, including an examination of fading and distortion, and the instrumentation used in the analysis of link performance. Multipath fading, the different categories, as well as the causes and effects thereof, are reviewed. The Tellurometer Method of distance measurement is described and its suitability to path analysis discussed.
22
Ishii, T. Koryu. "Sensing of Irregularities on Fast Moving Surfaces by Microwaves and Millimeterwaves." International Foundation for Telemetering, 1988. http://hdl.handle.net/10150/615034.
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International Telemetering Conference Proceedings / October 17-20, 1988 / Riviera Hotel, Las Vegas, NevadaFine cracks and irregularities on a fast moving conducting surface were detected by the use of microwave and millimeter wave radio responder techniques. The interrogation angle was restricted to an oblique incidence angle less than ±0.5 degree from the surface. The fast moving conducting surface was surrounded by both fast moving and stationary reflective conducting structures. Experimental methods and results from a fine crack 0.1 mm wide, 0.9 mm deep, and 25 mm long on a conducting surface travelling with a speed of 20.23 m/s and measured at 10.525 GH(z) and 73 GH(z) are presented. The reflection-type microwave radio responder consisted of a 10.525 GH(z) 50 mW Gunn diode cw transmitter, a circulator, and a horn antenna used as the interrogator. The receiver in the same responder consisted of the same horn antenna, the circulator and detector diode. The detector diode output was observed with a Norland 3106R digital memory oscilloscope. A reflex kylstron VA 250 was used as the transmitter signal source for the millimeter wave responder. There was a distinct difference between the responder output patterns with uncracked and cracked surfaces. It is therefore possible to use this type of responder for hair-line crack detection of fast moving conducting surfaces. It was also found that this type of radio responder can detect the surface irregularity even before the hairline crack actually occurs.
23
Badiere, Daniel N. "A study of high Q spiral inductor fabrication methods using a production silicon process with application to a current tuned microwave oscillator /." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/MQ61016.pdf.
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Lyson, Kyle Joshua. "On-chip automatic tuning of CMOS active inductors for use in radio frequency integrated circuit (RFIC) applications." Thesis, Montana State University, 2006. http://etd.lib.montana.edu/etd/2006/lyson/LysonK1206.pdf.
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Aflaki, Beni Aman. "35-45 giga hertz transceiver system for phase and magnitude detection." Diss., Rolla, Mo. : University of Missouri-Rolla, 2007. http://scholarsmine.mst.edu/thesis/pdf/Aman_aflaki_Final_thesis_09007dcc8034dd48.pdf.
Повний текст джерелаАнотація:
Thesis (M.S.)--University of Missouri--Rolla, 2007.Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed November 14, 2007) Includes bibliographical references (p. 118-119)
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Davé, Pratik K. (Pratik Kamlesh). "Using a co-located GNSS radio occultation payload for microwave radiometer calibration." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/93798.
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Thesis: S.M., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, 2014.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 55-58).
This study presents a new method of calibrating an orbital cross-track scanning microwave radiometer using a co-located radio occultation (RO) instrument with Global Navigation Satellite Systems (GNSS). The radiometer and RO receiver periodically observe the same volume of atmosphere near the earth's limb, allowing for overlapping, or collocated, measurements that can be used to calibrate the radiometer. This method leverages the benefits of both remote sensing techniques to strengthen the science returned with the goal of achieving dense geospatial sampling and highly accurate calibration. Performance analyses show that the technique is particularly well-suited for implementation on a low-cost CubeSat hosting both radiometer and RO receiver systems on the same spacecraft. We describe a validation platform for this calibration method, the Microwave Radiometer Technology Acceleration (MiRaTA) CubeSat, currently in development by MIT Lincoln Laboratory and MIT Space Systems Laboratory for the NASA Earth Science Technology Office. MiRaTA will fly a multi-band radiometer and the Compact TEC/Atmosphere GPS Sensor (CTAGS) in 2016. We investigate the effect of system design parameters such as hardware specifications and operational concepts on the performance of this co-located remote sensing method.
by Pratik K. Dave.
S.M.
27
Zhou, Mi. "Multi-Function and Flexible Microwave Devices." Thesis, University of North Texas, 2018. https://digital.library.unt.edu/ark:/67531/metadc1404604/.
Повний текст джерелаАнотація:
In this dissertation, some multi-function and flexible RF/microwave devices have been studied to solve the issues in the modern microwave system designs. First, a power divider with two functions is proposed. The first function is a zero-phase delay power divider using zero-phase impedance transformer. The second function is a power divider with impedance transforming property. To achieve the first function, the two arms are treated as zero-phase impedance transformers. When the phase requirement is relaxed, the second function is obtained. Shunt transmission line stubs are employed to connect the isolation resistor, which provides great flexibility in the design. Then, a balun with transparent termination impedance and flexible open arms is designed. The design parameters of the balun are independent to the port impedance. This property allows the balun to work with different system impedances. Furthermore, the two output ports of the balun do not need to be connected together, which enables the device to have a very flexible structure. Finally, the continuous research of a tunable/reconfigurable coupler with equal output impedance is presented. In addition to the tunable/reconfigurable responses, unequal output impedance property is added to the microstrip line coupler. To shrink the size at the low frequency and make it easy for fabrication at higher frequency, the coupler is redesigned using lumped components. To validate the design theories, simulations are carried out. Moreover, prototypes of the power divider and the balun are fabricated and characterized. The simulation and measurement results match well with the theoretical calculation.
28
Blair, Arthur Paul Jr. "A broadband Microwave Transceiver Front-end for an Airborne Software Defined Radio Experiment." Thesis, Virginia Tech, 2015. http://hdl.handle.net/10919/51226.
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This document describes the design, simulation, construction, and test of a wideband analog transceiver front-end for use in an airborne software defined radio (SDR) experiment. The transceiver must operate in the GSM-1800 and IEEE 802.11b/g WiFi frequency bands and accommodate beamforming. It consists of a transmitter and dual band receiver. The receiver input is fed by a helical antenna and the outputs are digitized for use in the SDR. The transmitter is fed by a complex baseband output from a Digital-to-Analog Converter (DAC) and its output fed to another helical antenna. The requirements for the transceiver were driven by a spectral survey of the operating environment and the physical and electrical limitations of the platform. The spectral survey showed a great disparity in the received power levels between the signals of interest and potential interferers. Simulations of several candidate receiver architectures showed that meeting the needs of the experiment would require a high degree of linearity and filtering. It was found that the receiver requirements could be met by a single downconversion with high order filters and passband sampling. A series of analyses determined the requirements of the individual components that make up the system. Performance was verified by simulations using measured data of the individual components and lab tests of the assembled hardware. Suggestions for improved performance and expanded operation are made.Master of Science
29
Birla, Sohan L. "Potential of radio frequency heating of fresh fruits as an alternative quarantine method." Online access for everyone, 2006. http://www.dissertations.wsu.edu/Dissertations/Fall2006/s_birla_010807.pdf.
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Anderson, Martin William Bruce 1965, University of Western Sydney, of Science Technology and Environment College, and School of Computing and Information Technology. "A radio survey of selected fields from the ROSAT All Sky Survey." THESIS_CSTE_CIT_Anderson_M.xml, 2002. http://handle.uws.edu.au:8081/1959.7/359.
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The beginning of X-ray astronomy is based on two accidental discoveries made in 1962. A single point source, Scorpio X-1 and remarkable discovery of the diffuse background radiation, three years before the microwave background was discovered. Over the past four decades, X-ray astronomy has matured into a major branch of astronomy, contributing to our understanding of the physical processes operating in many different types of sources, from stars to high redshift quasars. In 1990, the launch of the ROSAT satellite offered to unique opportunity to investigate the radio properties of X-ray emitters. A sample of faint X-ray emitters from a deep pointed observation is used in this thesis to investigate the prediction that sub-mJy radio source are a major contributor to the X-ray background. Another sample of 695 bright X-ray emitters were selected from ROSAT All Sky Survey for optical follow-up as a European Southern Observatory key project. The radio follow-up of the sample was undertaken for this thesis. The aim is to construct a catalogue of radio emitting X-ray (REX) sources to study their quantitative statistical properties and to select out a sample of BL-Lac objects for further study. Based on previous surveys approximately 19% or 130 of the X-ray sources should be directly associated with a radio emitter, of which 90% will be positionally coincident with the most plausible optical candidate for an X-ray source. This increases the efficiency of the optical identification program by about 15 percent.Doctor of Philosophy (PhD)
31
Leung, Lydia Lap Wai. "Low-loss on-chip interconnects for silicon integrated radio-frequency and microwave systems /." View abstract or full-text, 2005. http://library.ust.hk/cgi/db/thesis.pl?ELEC%202005%20LEUNG.
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Naji, Adham. "On the design of reconfigurable microwave resonators and filters for advanced radio systems." Thesis, University of Bristol, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.509762.
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Kent, Antony Norman. "The influence of radio refractive index on angle-of-arrival at microwave frequencies." Thesis, University of Essex, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.304545.
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Wu, Yichao. "RF circuit applications of enhancement-mode AlGaN/GaN HEMTs /." View abstract or full-text, 2007. http://library.ust.hk/cgi/db/thesis.pl?ECED%202007%20WUY.
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Stephens, Richard Brian Leonard. "A study and modelling of the propagation effects of vegetation on radio waves at centimetre-wavelength frequencies." Thesis, University of South Wales, 1998. https://pure.southwales.ac.uk/en/studentthesis/a-study-and-modelling-of-the-propagation-effects-of-vegetation-on-radio-waves-at-centimetrewavelength-frequencies(48d8248f-a287-45e4-96e5-fe8d8e56efae).html.
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With the increase in and more diverse applications of microwave radio communications, the probability of a signal propagating through a medium of vegetation is increased. As a direct result of this demand for microwave communication systems, knowledge is required of the effects of vegetation media on the propagating microwave signal. This enables radio system planners to predict the signal loss more accurately, necessitating a detailed study of the propagation effects of vegetation. A vegetation depth attenuation model has been developed based on the International Telecommunications Union-Radio Sector model and validated against measurements conducted at two microwave frequencies of 11.2 GHz and 20 GHz. The measurements were conducted on a number of sites of differing geometries at different times of the year to obtain the two extreme states of foliage, in- and out-of-leaf. The trees found at the sites were of a number of indigenous species. A variety of species and environments were employed for the outdoor measurements as it was felt that any variation in the signal, occurring as a direct result of the species, climate, environment etc., would be reduced. A further study has been conducted in an anechoic chamber, the purpose being to investigate the depolarising effect of vegetation, to characterise and to ascertain how and to what extent the polarisation of the incident signal is changed as it passes through the vegetation without the effects of climate, location and environment affecting the resultant signal. To enable larger quantities of data to be obtained, collated and subsequently analysed and also to remove any scope for error during the collection of results, two data acquisition programs were written for the two main environments in which the measurements were to be undertaken, that is to say, outdoor and indoor (anechoic chamber) environments. In seeking to provide a model for the prediction of attenuation a radio wave will suffer as it is propagated through a body of vegetation, several models have been examined in turn and their relative merits discussed together with their applicability to the study. After examining the possible models available, the thesis provides a model which enables the prediction of additional attenuation a radiowave signal will suffer as a function of path length (depth) of the vegetation medium and frequency. The model can be recommended for use in the 10-30 GHz band. The study on the depolarisation of signals by vegetation has shown that the components of a vegetation medium e.g. tree trunks, branches and leaves, can cause considerable changes in the polarisation of the incident signal as it propagates through a volume of vegetation. The work presented in this thesis contains new measured results of the polarisation state of the radio wave as it emerges from a vegetation specimen. These results obtained in an anechoic chamber under controlled conditions have demonstrated that additional effects, other than attenuation by absorption and scatter need to be considered in order to characterise and subsequently model the overall effect of vegetation in the radio path of propagating signals.
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Brown, Keith Edgar. "The application of knowledge-based techniques to fault diagnosis of 16 QAM digital microwave radio equipment." Thesis, University of Edinburgh, 1988. http://hdl.handle.net/1842/12958.
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Li, Jia, and 李佳. "Photonic microwave processor based on fiber optical parametric amplifier." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2009. http://hub.hku.hk/bib/B43085374.
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Li, Jia. "Photonic microwave processor based on fiber optical parametric amplifier." Click to view the E-thesis via HKUTO, 2009. http://sunzi.lib.hku.hk/hkuto/record/B43085374.
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Kermoal, John Phillipe. "Coherence bandwidth characterisation for indoor mobile radio microcells at microwave and millimetre wave frequencies." Thesis, University of South Wales, 1998. https://pure.southwales.ac.uk/en/studentthesis/coherence-bandwidth-characterisation-for-indoor-mobile-radio-microcells-at-microwave-and-millimetre-wave-frequencies(f01885d8-8010-4a49-a3e3-356e01911a46).html.
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This thesis reports measured and predicted results of the coherence bandwidth of indoor mobile radio microcells at 11 GHz and 62.4 GHz. Furthermore, the influence of the antennas radiation patterns and the effect of furniture on the value of the coherence bandwidth has been investigated. A two branch frequency diversity system has been developed and used to simultaneously record the amplitude variation of the sideband signals. Frequency separations in the range between 5 and 240 MHz have been used at both 11 GHz and 62.4 GHz. In order to assist in explaining experimental results, a ray-tracing algorithm based on the image method, has been developed. It considers reflections up to the third order and assumes smooth walls, all with the same dielectric parameters. The correlation coefficients between signal envelopes separated in frequency are measured and expressed as functions of distance between terminals. The level below which the correlation stays for a given percentage of time has been measured and plotted against frequency spacing to generate the frequency correlation function of the microcell. The coherence bandwidth, corresponding to correlation levels of 0.5, 0.7 and 0.9, are determined from these functions. The coherence bandwidth has also been measured at each position in the microcell and its value for a given percentage of mobile terminal locations is given. The difference between results obtained from both methods are outlined and explained. Results are presented for three corridors and a room. A comparison between experimental results obtained at 11 GHz and 62.4 GHz is also given.
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Zhou, Mi. "Design of Tunable/Reconfigurable and Compact Microwave Devices." Thesis, University of North Texas, 2014. https://digital.library.unt.edu/ark:/67531/metadc500093/.
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With the rapid development of the modern technology, radio frequency and microwave systems are playing more and more important roles. Since the time the first microwave device was invented, they have been leading not only the military but also our daily life to a new era. In order to make the devices have more practical applications, more and more strict requirements have been imposed. For example, good adaptability, reduced cost and shrank size are highly required. In this thesis, three devices are designed based on this requirement. At first, a symmetric four-port microwave varactor based 90-degree directional coupler with tunable coupling ratios and reconfigurable responses is presented. The proposed coupler is designed based on the modified structure of a crossover, where varactors are loaded. Then, a novel reconfigurable 3-dB directional coupler is presented. Varactors and inductors are loaded to the device to realize the reconfigurable performance. By adjusting the voltage applied to the varactors, the proposed coupler can be reconfigured from a branch-line coupler (90-degree coupler) to a rat-race coupler (180 degree coupler) and vice versa. At last, two types (Type-I and Type-II) of microwave baluns with generalized structures are presented. Different from the conventional transmission-line-based baluns where λ/2 transmission lines or λ/4 coupled lines are used, the proposed baluns are constructed by transmission lines with arbitrary electrical lengths.
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Mcculloch, Mark Anthony. "Enhancing the noise performance of low noise amplifiers : with applications for future cosmic microwave background observatories." Thesis, University of Manchester, 2014. https://www.research.manchester.ac.uk/portal/en/theses/enhancing-the-noise-performance-of-low-noise-amplifiers--with-applications-for-future-cosmic-microwave-background-observatories(cd1da9b9-af7f-4bd2-a797-766c02855ab9).html.
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Low Noise Amplifiers (LNAs) are one of the most important components found in some of the radio receivers used in radio astronomy. A good LNA should simultaneously possess both a gain in excess of 25\,dB and as low a noise contribution as possible. This is because the gain is used to suppress the noise contribution of the subsequent components but the noise generated by the LNA adds directly to the noise of the overall receiver. The work presented in this thesis aimed to further enhance the noise performance through a variety of techniques with the aim of applying these techniques to the study of the polarisation of the Cosmic Microwave Background. One particular technique investigated was to cool the LNAs beyond the standard 20\,K typically used in experiments to 2\,K. In doing so it was found that the noise performance increased by between 20 and 30\% depending on the amplifier. Another technique investigated involved uniting the two technologies (MICs and MMIC) used in LNA fabrication to lower the noise performance of the LNA. Such an LNA, known as a T+MMIC LNA was successfully developed and possessed an average noise temperature of 9.4\,K and a gain in excess of 40\,dB for a 27-33\,GHz bandwidth at 8\,K physical temperature. Potential ``in field'' applications for these technologies are discussed, and a design for a variant of the T+MMIC LNA that utilises both of these technologies is presented. This particular LNA with a predicted average noise temperature of 6.8\,K for a 26-36\,GHz bandwidth, would if fabricated successfully represent the lowest noise Ka-band LNA ever reported.
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Azhar, Ahmad Helmi. "Visible light commuinications using optical OFDM." Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:9e4c363b-27ba-4e47-8660-39f4e0a077f8.
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This thesis presents an investigation into designs and developments of indoor visible light communication (VLC) systems using orthogonal frequency division multiplexing (OFDM) schemes. The novel contribution of this thesis is a development of a visible light communication system that incorporates OFDM and imaging-diversity multiple-input multiple-output (MIMO) techniques, which allows robust transmissions on multiple channels at high data rates. The characteristics of VLC systems are presented, one of which is VLC communications channel exhibits high Signal-to-Noise Ratio (SNR). The major constraint however, is the low modulation bandwidth of typical high power white LED sources. The performance of OFDM as a modulation scheme is investigated. OFDM offers the possibility for bit and power loading to increase bandwidth efficiency, as well as a straightforward equalisation in time and frequency domains to compensate the low pass frequency response of the LED. This allows transmission rates of up to ~310Mbps at a BER of 2x10-3 on a single-channel link using 16- QAM DCO-OFDM. Further increase in data rates for this transmission is constrained by the available signal power due to a dynamic range limitation at the receiver. An increase in signal power will results in the OFDM waveform to be clipped, which incurs a clipping noise. MIMO systems offer a linear capacity gain to a number of transmission channels in an ideal configuration. These systems mitigate the dynamic range limitation, as power is divided between multiple channels. The performance of a MIMO transmission system is investigated under the same dynamic range constraint. A 4-channel MIMO transmitter is built using four sets of transmitter components of the single-channel link. An imaging system is used to separate the received optical power onto multiple detectors, and MIMO processing relaxes the requirements for precise mechanical alignments. The experiment has shown that the imaging MIMO system further improves data rates and transmissions of up to ~1.1Gigabit/s at a BER of 2x10-3 are achieved. To the best of the author’s knowledge, this is the highest reported for an indoor VLC MIMO-OFDM transmission. Also presented is an analysis of MIMO system scalability to provide room-wide coverage. Finally, this thesis presents an extended analysis of several other optical OFDM approaches, and concludes with recommendations of future work to increase the data rates of indoor VLC systems.
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Zhang, Fan. "Diversity strategies for MIMO communication systems." Thesis, University of Oxford, 2010. http://ora.ox.ac.uk/objects/uuid:530327bb-e4d9-4ce2-8140-312e7d175c05.
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This thesis proposes a joint spatial diversity scheme in MIMO systems in order to improve the transmission reliability of the wireless links, thereby to extend the transmission range and increase the information throughput. Cyclic delay diversity (CDD) and antenna selection are employed here for their low complexity, high flexibility, no spectrum efficiency reduction and high compatibility with many existing standards. A bit error performance bound for CDD system with orthogonal frequency division multiplexing and convolutional coding in multipath Rayleigh fading channel is generated, which renders a fundamental understanding of the mechanism of CDD and can be used instructively for CDD system design. A transmit cyclic delay diversity and receive antenna selection (TCDD/RAS) system is proposed here to achieve a performance gain with lower additional complexity and no data rate reduction compared with a transmit orthogonal space-time block coding (OSTBC) system, which is combined with the optimum receive antenna selection scheme. A hybrid system with both OSTBC and CDD in the transmitter and antenna selection in the receiver is also derived to avoid the high complexity requirement and data rate degradation of the OSTBC system as well as the performance loss of the CDD system. A receive antenna selection criterion for the TCDD/RAS system based on the previous performance analysis results is defined, however it demands high computational complexity. Therefore a much simpler and faster selection rule, named maximum minimum post-processing SNR criterion, is generated for the TCDD/RAS system in flat fading channels and another maximum group minimum post-processing SNR selection principle is developed in frequency selective channels. Both of these two selection rules achieve higher diversity gains with lower additional complexity compared with the traditional norm and capacity selection rules. Two relay systems embedded with the TCDD/RAS scheme are also constructed: the MIMO relay system and the cooperative relay system. The joint diversity scheme in the MIMO relay system obtains a higher diversity gain than in the cooperative relay system. Moreover, these two relay systems could be combined to a system with multiple cooperative relay nodes on which multiple antennas are deployed depending on the practical requirement in the future wireless communication systems.
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O'Connor, Kevin A. Curry Randy D. "Compact power conditioning and RF systems for a high power RF source." Diss., Columbia, Mo. : University of Missouri--Columbia, 2008. http://hdl.handle.net/10355/6285.
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Title from PDF of title page (University of Missouri--Columbia, viewed on Feb. 19, 2010). The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file. Dr. Randy Curry, Thesis Supervisor Includes bibliographical references.
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Zhu, Jiwen. "Design and application of novel metamaterial elements and configurations." Thesis, University of Oxford, 2011. http://ora.ox.ac.uk/objects/uuid:8410f555-3a06-49c7-8734-084f34cab129.
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Metamaterials are artificially constructed "materials" which are formed from arrays of engineered elements. By designing individual elements as well as their interactions, the propagation of electromagnetic (EM) waves within the structure can be manipulated, so that new responses can be realised which may not be found in nature. The subject of this research concerns the study of miniaturised elements with strong EM responses so that the constructed metamaterial can better approximate an ordinary low-loss material. The research involves designing miniaturised magnetic resonators operating in the microwave frequency range. A novel resonator prototypes, so-called “helical resonators”, have been successfully designed and fabricated whose physical sizes can fall below 1% of the free space wavelength at resonance. This contributes to a size reduction of 90% compared with previously published work. In addition, an analytical model has been developed, so that the resonance parameters of a helical resonator have explicit expressions. In particular, a constant optimal metallic fill ratio is demonstrated to exist, which can achieve a minimum resonant frequency and a maximum miniaturisation for any given outmost dimension of the element. The accuracy of the model has been verified by both simulation and experiment. The frequency responses of fabricated helical elements were measured using a vector network analyser and a pair of small loop non- resonant dipole probes, and the parameters were extracted using the phase frequency fit method which proves to have the best accuracy and robustness. The properties of a regular square array of helical resonators are subsequently investigated, which can be regarded as a two-dimensional metamaterial. A relevant analytical model has been developed, which characterises the array as an equivalent sheet with surface current distributions, rather than an artificial medium with finite thickness. The relation between the macroscopic EM fields and the small scale properties of individual helical resonators are then established. In particular, the helical resonators are observed to be inherently chiral, thus the assembled interlocking array exhibits dichroism. The transmission coefficients for the circular EM waves with two different polarisation states have been derived, which have been verified by simulation and measurement results as well. In addition, it has been theoretically demonstrated that the resonator elements and their spacings can be engineered, so that the circular EM wave with one particular polarisation state can be totally attenuated around the element resonance, while the other state suffers negligible attenuation. A quadratic relation between the optimal array spacing and the elements’ quality factor has been demonstrated.
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Mills, John Brean. "Composite materials for microwave frequency agile planar devices." Thesis, University of Oxford, 2003. http://ora.ox.ac.uk/objects/uuid:213e4e33-2816-470f-bb8d-9b36d50e1254.
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The potential of Calcium-Vanadium garnet loaded binary composites for use in the production of planar frequency agile microwave devices has been investigated. A WR90 rectangular waveguide system using the transmission/reflection technique has been used to compare effective medium theory predicted permittivities and permeabilities for unmagnetised and transversely magnetised composites with actual measured composite properties. Use of the the Bruggeman effective medium theory with manufacturer supplied garnet permittivity and values of garnet permeability calculated using simple empirical models were demonstrated to be as accurate as predictions made using the measured properties of the composites' individual constituents. Errors in predicted material properties for unmagnetised and transversely magnetised samples relative to measured data were less than 5% across almost half of the 8.2 -12.4GHz measurement band and within a worst-case error of 15% across the whole band. A series of end-coupled linear microstrip resonators using garnet-loaded composite substrates has been fabricated and tested. Tunabilities in resonance of up to 3.9% at 9.2GHz have been demonstrated for DC magnetic bias fields applied transverse to the microwave magnetic field component. An entirely new and previously unpublished broadband microstrip technique for the measurement of the effective permittivity and permeability of bulk gyromagnetic and gyromagnetic material loaded composite substrates subject to transverse DC magnetic bias fields is presented. This will have wide application in the design of frequency agile microwave integrated circuits.
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D'Souza, Mark Francis. "Residential Microwave Oven Interference on Bluetooth Data Performance." Thesis, Virginia Tech, 2002. http://hdl.handle.net/10919/31935.
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This thesis investigates the interference potential of microwave ovens to Bluetooth data communication. Interference experiments are conducted in the CWTâ s Bluetooth lab, using CSRâ (Cambridge Silicone Radio) Bluetooth radios and a Tektronicsâ Protocol Analyzer to record packet transmissions between the master and slave units.
A novel, â quasi-real timeâ spectral measurement concept is developed to take radio frequency measurements. A LabView program enables a spectrum analyzer to download oven spectral data onto a computer via the instrumentâ s serial port. From this data, three-dimensional plots of microwave radiated power levels versus ISM band frequencies over time periods are produced for different microwave ovens. These plots are compared with the results of interference experiments to explain Bluetooth packet errors.
In addition to causing packet errors, emitted oven power levels at certain frequencies are sometimes strong enough to cause data packets to be lost (dropped) as they are transmitted over the air. This is a major problem since the Protocol Analyzer does not â seeâ these packets and cannot record the transmissions during an experiment. These lost packets can be accounted for if the frequency hopping scheme of the communicating Bluetooth devices is know prior to data transmission. Bluetoothâ s Frequency Hop Scheme is coded in Matlab for the purpose of predicting a data transmissionâ s hopping sequence. The lost packets on each Bluetooth channel are counted by subtracting the Analyzerâ s recorded number of data transmissions per channel from the total number of transmissions per channel predicted by Matlab.
A method is devised to calibrate the Bluetooth receiver and the spectrum analyzer is used to measure the received power level of Bluetooth signals on a particular frequency (channel). The number of packet errors on a channel is determined from the channelâ s C/I (carrier-to-interference ratio). If a channelâ s C/I level falls below the calculated C/I threshold at any instant of time due to oven operation, the packet transmitted at that instant is likely in error. A Matlab program estimates the number of packet errors per channel by counting the number of times the C/I of a channel falls below itâ s threshold value. The predicted number of packet errors is compared with the measured packet errors from experiments to yield extremely good results.
Various oven-interference experiments are conducted in a small building, a large office environment and outdoors. For each experiment, the number of occurrences of transmitted data is plotted for each Bluetooth channel. Composite Excel bar graphs, created from this data, are compared with the oven spectral plots to describe an ovenâ s effect on Bluetooth transmission.
It is determined that different ovens cause packet errors on specifically different channels, in addition to channels 52-54 around the ovenâ s 2450 MHz center operating frequency. The interference experiments suggest that placing an oven a radius of 10 m away from Class I (devices in a piconet will not affect data transmission).Master of Science
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Bulzacchelli, John F. (John Francis). "A superconducting bandpass delta-sigma modulator for direct analog-to-digital conversion of microwave radio." Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/16949.
Повний текст джерелаАнотація:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2003.Includes bibliographical references (p. 291-305).
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Direct analog-to-digital conversion of multi-GHz radio frequency (RF) signals is the ultimate goal in software radio receiver design but remains a daunting challenge for any technology. This thesis examines the potential of superconducting technology for realizing RF analog-to-digital converters (ADCs) with improved performance. A bandpass delta-sigma (AE) modulator is an attractive architecture for digitizing narrowband signals with high linearity and a large signal-to-noise ratio (SNR). The design of a superconducting bandpass AE modulator presented here exploits several advantages of superconducting electronics: the high quality factor of resonators, the high sampling rates of comparators realized with Josephson junctions, natural quantization of voltage pulses, and high circuit sensitivity. Demonstration of a superconducting circuit operating at clock rates in the tens of GHz is often hindered by the difficulty of high speed interfacing with room-temperature test equipment. In this work, a test chip with integrated acquisition memory is used to simplify high speed testing in a cryogenic environment. The small size (256 bits) of the on-chip memory severely limits the frequency resolution of spectra based on standard fast Fourier transforms. Higher resolution spectra are obtained by "segmented correlation", a new method for testing ADCs. Two different techniques have been found for clocking the superconducting modulator at frequencies in the tens of GHz. In the first approach, an optical clocking technique was developed, in which picosecond laser pulses are delivered via optical fiber to an on-chip metal-semiconductor-metal (MSM) photodiode, whose output current pulses trigger the Josephson circuitry. In the second approach, the superconducting modulator is clocked by an on-chip Josephson oscillator.
(cont.) These testing methods have been applied in the successful demonstration of a super-conducting bandpass AE modulator fabricated in a niobium integrated circuit process with 1 kA/cm2 critical current density for the Josephson junctions. At a 42.6 GHz sampling rate, the center frequency of the experimental modulator is 2.23 GHz, the measured SNR is 49 dB over a 20.8 MHz bandwidth, and a full-scale (FS) input is -17.4 dBm. At a 40.2 GHz sampling rate, the measured in-band noise is -57 dBFS over a 19.6 MHz bandwidth.
by John Francis Bulzacchelli.
Ph.D.
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Somasundaram, Meena Sivalingam. "Pulsed power and load-pull measurements for microwave transistors." [Tampa, Fla] : University of South Florida, 2009. http://purl.fcla.edu/usf/dc/et/SFE0003293.
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Huo, Xiao. "High performance passive components modeling and integration in RF/microwave systems /." View abstract or full-text, 2005. http://library.ust.hk/cgi/db/thesis.pl?ELEC%202005%20HUO.
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