Design and Implementation of a Re-Configurable Arbitrary Signal Generator and Radio Frequency Spectrum Analyser

This research is focused on the design, simulation and implementation of a reconfigurable arbitrary signal generator and the design, simulation and implementation of a radio frequency spectrum analyser based on digital signal processing. Until recently, Application Specific Integrated Circuits (ASICs) were used to produce high performance re-configurable function and arbitrary waveform generators with comprehensive modulation capabilities. However, that situation is now changing with the availability of advanced but low cost Field Programmable Gate Arrays (FPGAs), which could be used as an alternative to ASICs in these applications. The availability of high performance FPGA families opens up the opportunity to compete with ASIC solutions at a fraction of the development cost of an ASIC solution. A fast digital signal processing algorithm for digital waveform generation, using primarily but not limited to Direct Digital Synthesis (DDS) technologies, developed and implemented in a field-configurable logic, with control provided by an embedded microprocessor replacing a high cost ASIC design appeared to be a very attractive concept. This research demonstrates that such a concept is feasible in its entirety. A fully functional, low-complexity, low cost, pulse, Gaussian white noise and DDS based function and arbitrary waveform generator, capable of being amplitude, frequency and phase modulated by an internally generated or external modulating signal was implemented in a low-cost FPGA. The FPGA also included the capabilities to perform pulse width modulation and pulse delay modulation on pulse waveforms. Algorithms to up-convert the sampling rate of the external modulating signal using Cascaded Integrator Comb (CIC) filters and using interpolation method were analysed. Both solutions were implemented to compare their hardware complexities. Analysis of generating noise with user-defined distribution is presented. The ability of triggering the generator by an internally generated or an external event to generate a burst of waveforms where the time between the trigger signal and waveform output is fixed was also implemented in the FPGA. Finally, design of interface to a microprocessor to provide control of the versatile waveform generator was also included in the FPGA. This thesis summarises the literature, design considerations, simulation and implementation of the generator design. The second part of the research is focused on radio frequency spectrum analysis based on digital signal processing. Most existing spectrum analysers are analogue in nature and their complexity increases with frequency. Therefore, the possibility of using digital techniques for spectrum analysis was considered. The aim was to come up with digital system architecture for spectrum analysis and to develop and implement the new approach on a suitable digital platform. This thesis analyses the current literature on shifting algorithms to remove spurious responses and highlights its drawbacks. This thesis also analyses existing literature on quadrature receivers and presents novel adaptation of the existing architectures for application in spectrum analysis. A wide band spectrum analyser receiver with compensation for gain and phase imbalances in the Radio Frequency (RF) input range, as well as compensation for gain and phase imbalances within the Intermediate Frequency (IF) pass band complete with Resolution Band Width (RBW) filtering, Video Band Width (VBW) filtering and amplitude detection was implemented in a low cost FPGA. The ability to extract the modulating signal from a frequency or amplitude modulated RF signal was also implemented. The same family of FPGA used in the generator design was chosen to be the digital platform for this design. This research makes arguments for the new architecture and then summarises the literature, design considerations, simulation and implementation of the new digital algorithm for the radio frequency spectrum analyser

Phase modulating interferometry with stroboscopic illumination for characterization of MEMS

This Thesis proposes phase modulating interferometry as an alternative to phase stepping and phase-shifting interferometry for use in the shape and displacement characterization of microelectromechanical systems (MEMS) [Creath, 1988; de Groot, 1995a; Furlong and Pryputniewicz, 2003]. A phase modulating interferometer is developed theoretically with the use of a stroboscopic illumination source and implemented on a Linnik configured interferometer using a software control package developed in the LabVIEWâ„¢ programming environment. Optimization of the amplitude and phase of the sinusoidal modulation source is accomplished through the investigation and minimization of errors created by additive noise effects on the recovered optical phase. A spatial resolution of 2.762 µm over a 2.97x2.37 mm field of view has been demonstrated with 4x magnification objectives within the developed interferometer. The measurement resolution lays within the design tolerance of a 500Ã… ±2.5% thick NIST traceable gold film and within 0.2 nm of data acquired under low modulation frequency phase stepping interferometry on the same physical system. The environmental stability of the phase modulating interferometer is contrasted to the phase stepping interferometer, exhibiting a mean wrapped phase drift of 40.1 mrad versus 91 mrad under similar modulation frequencies. Shape and displacement characterization of failed µHexFlex devices from MIT\u27s Precision Compliant Systems Laboratory is presented under phase modulating and phase stepping interferometry. Shape characterization indicates a central stage displacement of up to 7.6 µm. With a linear displacement rate of 0.75 Ã…/mV under time variant load conditions as compared to a nominal rate of 1.0 Ã…/mV in an undamaged structure [Chen and Culpepper, 2006]

Telecommunications Division

Spacecraft telecommunication systems - coding methods for phase locked loops, absolute time determination by pulsar, communications elements researc

Engineering evaluations and studies. Volume 3: Exhibit C

High rate multiplexes asymmetry and jitter, data-dependent amplitude variations, and transition density are discussed

Electromagnetic guidance study

Electromagnetic sensors for guidance and control during spacecraft dockin

Impact of Radio Frequency Interference and Real-Time Spectral Kurtosis Mitigation

We catalog the ubiquity of Radio Frequency Interference (RFI) plaguing every modern radio telescope and investigate several ways to mitigate it in order to create better science-ready data products for astronomers. There are a myriad of possible RFI sources, including satellite uplinks and downlinks, cellular communications, air traffic radar, and natural sources such as lightning. Real-time RFI mitigation strategies must take these RFI characteristics into account, as the interfering signals can look significantly different at very high time and frequency resolutions. We examine Spectral Kurtosis (SK) as a real-time statistical RFI detection method, and compare its flagging efficacy against simulated RFI witha wide range of signal characteristics. We found to be weak against signals with a 50% effective duty cycle, as well as low signal-to-noise ratio sidelobe spillover from strong and frequency-wide RFI. Coarsening the SK time resolution improved flagging, as did using multi-scale SK, which averages adjacent time-frequency pixels with small rolling windows to circumvent the weakness to 50% duty cycle signals. Multiscale SK raised flagging above 90% for almost all cases, and as long as the amount of channels included in the multi-scale window wasn’t wider than the RFI signal, there was no significant increase in false positive rate. Simulated realistic incoherent astronomical signals were not detected by SK at all, as expected. To simulate real-time SK RFI detection in a real data set, raw, unaveraged data was taken with the Robert C. Byrd Green Bank Telescope (GBT). The observation targets included one pulsar, two neutral hydrogen (HI) galaxies, the Milky Way HI emission, and a hydroxyl megamaser. These targets are all easily observable on short timescales but are also nearby several sources of RFI. Flagged data was replaced with representative Gaussian noise using the statistics of adjacent time-frequency pixels. We run different variations of SK detection on copies of the raw datasets and compared to the original, to see how well the RFI was removed and if the science data product was affected in any way. The spectral line targets are all completely ignored by SK , while the pulsar results decreased in quality due to the noise replacement averaging over the time variable structure, unless care was taken to flag data on timescales shorter than the pulse length. In these cases, single pulse signal-to-noise ratio was marginally improved

Introduction to Communication Systems Using National Instruments Universal Software Peripheral Radio Lab Manual

The students at the University of New Mexico Electrical and Computer Engineering Department are planning to use an integrated set of lectures and labs to better understand basic communications systems. The lectures are based on the textbook by Ziemer and Tranter, Principles of Communications - Systems, Modulation, and Noise. The labs are developed using the National Instruments Universal Software Radio Peripheral (USRP). The choice of this radio provides 2 advantages from an instructional perspective: it minimizes the amount of lab equipment necessary for performing the labs, and its range of flexibility to support spectrum sensing, cognitive radio and alternate modulation schemes. (Párrafo extraído del texto a modo de resumen)Ibero-American Science and Technology Education Consortium (ISTEC

Detector Description and Performance for the First Coincidence Observations between LIGO and GEO

For 17 days in August and September 2002, the LIGO and GEO interferometer gravitational wave detectors were operated in coincidence to produce their first data for scientific analysis. Although the detectors were still far from their design sensitivity levels, the data can be used to place better upper limits on the flux of gravitational waves incident on the earth than previous direct measurements. This paper describes the instruments and the data in some detail, as a companion to analysis papers based on the first data.Comment: 41 pages, 9 figures 17 Sept 03: author list amended, minor editorial change

Impact of Atmospheric Propagation Effects on the Performance of Pulse Compression Techniques for Radar Systems

Currently, more than three tons of space debris are an integrate part of the low earth orbit, and exhibit a trend to increase, due to collisions and the constant inoperability of older satellite systems. The technological era that we are living, in which satellites are a major element of any Telecommunications service, it is necessary to make a sustainable use of Space, so that technology can keep improving. The European Space Surveillance and Tracking support framework has as its main objective the catalogue and prediction of space debris’ orbits, as a nonactive approach to the space debris problem. The rAdio TeLescope pAmpilhosa Serra (ATLAS) is incorporated on this framework, giving Portugal the capability of performing space debris detection and tracking. The main objective of this thesis was the creation of an Earth-space propagation simulator with frequency agility, so that it would be possible to simulate the propagation of many radar signals originated through pulse compression techniques and thus be able to quantify the impact of atmospheric propagation on its efficiency. To prove the profitability of using these techniques, two types of tests were carried out: a test using the ATLAS radar receiver circuit, providing a familiarization with this type of systems and afterwards, the obtainment of True Positive Rate curves, where it was demonstrated the high target detention capability when using pulse compression techniques compared to unmodulated radar pulses, mainly with very low SNR around -20dBAtualmente, mais de três toneladas de detritos espaciais são parte integrante da órbita baixa da Terra, apresentando uma tendência de aumento, devido à constante obsolescência de satélites mais antigos e possíveis colisões entre os mesmos. Na era tecnológica em que vivemos, em que os satélites são um elemento importante de qualquer serviço de telecomunicações, torna-se necessário fazer um uso sustentável do espaço, para que a tecnologia continue a evoluir. A estrutura europeia de apoio à vigilância e rastreamento espacial (EUSST) tem como principal objetivo a catalogação e previsão das órbitas dos detritos espaciais, sendo por isso considerada com uma abordagem não ativa de combate aos detritos espaciais. O rAdio TeLescope pAmpilhosa Serra (ATLAS) está incorporado nesta estrutura, proporcionando a Portugal a capacidade de realizar deteção e rastreamento de detritos espaciais. O principal objetivo desta tese passa pela criação de um simulador de propagação Terra-espaço, com agilidade em frequência, de forma a ser possível simular a propagação de vários sinais radar originados a partir de técnicas de compressão de impulsos, sendo assim capaz de quantificar o impacto da propagação atmosférica na eficiência dos mesmos. Para comprovar a rentabilidade do uso destas técnicas, foram realizados dois tipos de testes: um teste utilizando o circuito recetor do radar ATLAS, proporcionando uma familiarização com este tipo de sistemas e, posteriormente, a obtenção das curvas de percentagem de verdadeiros positivos, onde foi demonstrado a elevada capacidade de deteção de alvos ao utilizar técnicas de compressão de impulsos em comparação com impulsos de radar não modulados, principalmente para valores de SNR muito baixos, sensivelmente em torno de -20dB