Passive Synthetic Aperture Radar Imaging Using Commercial OFDM Communication Networks

Modern communication systems provide myriad opportunities for passive radar applications. OFDM is a popular waveform used widely in wireless communication networks today. Understanding the structure of these networks becomes critical in future passive radar systems design and concept development. This research develops collection and signal processing models to produce passive SAR ground images using OFDM communication networks. The OFDM-based WiMAX network is selected as a relevant example and is evaluated as a viable source for radar ground imaging. The monostatic and bistatic phase history models for OFDM are derived and validated with experimental single dimensional data. An airborne passive collection model is defined and signal processing approaches are proposed providing practical solutions to passive SAR imaging scenarios. Finally, experimental SAR images using general OFDM and WiMAX waveforms are shown to validate the overarching signal processing concept

A General Framework for Analyzing, Characterizing, and Implementing Spectrally Modulated, Spectrally Encoded Signals

Fourth generation (4G) communications will support many capabilities while providing universal, high speed access. One potential enabler for these capabilities is software defined radio (SDR). When controlled by cognitive radio (CR) principles, the required waveform diversity is achieved via a synergistic union called CR-based SDR. Research is rapidly progressing in SDR hardware and software venues, but current CR-based SDR research lacks the theoretical foundation and analytic framework to permit efficient implementation. This limitation is addressed here by introducing a general framework for analyzing, characterizing, and implementing spectrally modulated, spectrally encoded (SMSE) signals within CR-based SDR architectures. Given orthogonal frequency division multiplexing (OFDM) is a 4G candidate signal, OFDM-based signals are collectively classified as SMSE since modulation and encoding are spectrally applied. The proposed framework provides analytic commonality and unification of SMSE signals. Applicability is first shown for candidate 4G signals, and resultant analytic expressions agree with published results. Implementability is then demonstrated in multiple coexistence scenarios via modeling and simulation to reinforce practical utility

Design and Implementation of a UWB Radar Sensor for Non-Destructive Application

[ES] Debido a la importancia de los campos de aplicación del sensor de radar de banda ultraancha, y también a los requisitos de cada aplicación específica, existe una demanda creciente de diseño compacto, de bajo coste y alta precisión del sensor de radar de banda ultraancha. Para responder a estas exigencias, esta tesis pretende proponer un sensor de radar UWB avanzado. Este trabajo de investigación se centra en el diseño del sensor de radar de banda ultraancha (UWB) para aplicaciones no destructivas (END). Los detalles de diseño incluyen el diseño de un generador de pulsos ultracorto, de alta potencia con un timbre mínimo. El radar desarrollado fue construido con una configuración biestática. El objetivo de este trabajo es medir el rango de distancia y las propiedades eléctricas de un objetivo, por ejemplo, metales y materiales dieléctricos, como el cloruro de polivinilo (PV C). Para lograr este objetivo, se ha desarrollado un novedoso generador de pulsos de alta potencia ultra-corto (pulsador de radar). El nuevo generador de pulsos consiste en un transistor que funciona en modo de avalancha y un circuito de afilado de pulsos que utiliza un nuevo modelo de diodo de recuperación de paso (SRD). Para convertir el pulso gaussiano en un monociclo, se ha añadido una red de formación de monociclo (MFN). El generador de impulsos desarrollado produce un impulso eléctrico con una amplitud de 12 V, un tiempo de subida de 112 ps y un ancho de impulso (FWHM) de 155 ps. Con el fin de aumentar la amplitud de los pulsos, se han propuesto dos técnicas útiles en este trabajo. El primero consiste en agregar dos generadores en paralelo, en este diseño propuesto se tuvo en cuenta alguna especificación para hacer que este circuito funcione. Sin embargo, la segunda técnica adoptada en este trabajo consiste en dos etapas de generadores, ambas técnicas dan lugar a un buen rendimiento; en lugar de un solo módulo de un generador de impulsos, las técnicas propuestas en este trabajo aumentan la amplitud en torno al doble. Ambas técnicas han sido investigadas en detalle. Para transmitir y recibir los impulsos ultracortos generados, se utilizaron dos tipos diferentes de antenas UWB. En primer lugar, una antena Vivaldi con un ancho de banda de unos 5,5 GHz de 600 MHz a 6 GHz. La segunda es una antena Vivaldi con un ancho de banda de 6 GHz de 400 Mhz a 6,2 GHz. Utilizando el sensor de radar de banda ultraancha desarrollado, se realizaron mediciones de prueba. Esto incluye las propiedades eléctricas, así como la medición de la distancia a las placas de metal, madera y PVC. La incertidumbre del sensor de radar es de 14 mm (datos medidos asustados a + 14 mm para un blanco fijo). El diseño y la implementación real que conduce a lograr un excelente prototipo de rendimiento para una aplicación no destructiva.[CA] A causa de la rellevància dels camps d'aplicació del sensor de radar d'ultra banda ampla, i també l'exigència de cada aplicació específica, hi ha una demanda creixent de disseny compacte, de baix cost i alta precisió del sensor de radar d'ultra banda ampla. Amb la intenció d'atendre aquestes demandes, aquesta tesi pretén proposar un sensor avançat de radar UWB. Aquest treball de recerca tracta del disseny del sensor de radar d'ultra-banda ampla (UWB) per a aplicacions no destructives (NDT). Els detalls del disseny inclouen el disseny d'un pols de monocicle amb pols de potència d'alta potència i amb un mínim de timbre. El radar desenvolupat va ser construït en configuració bi-estàtica. L'objectiu d'aquest treball és mesurar el rang de distància i les propietats elèctriques d'un objectiu, per exemple, materials metàl·lics i dielèctrics, com el clorur de polivinil (PV C). Per assolir aquest objectiu, s'ha desenvolupat un nou ultrasò, generador de pols d'alta potència (polsador de radar). El nou generador de pols està format per un transistor que funciona en mode d'allaus i un circuit d'afilat de pols mitjançant un nou model de díode de recuperació de pas (SRD). Per a convertir el pols gaussiano en un monocicle, s'ha afegit una xarxa de formació de monocicles (MFN). El generador de polsos desenvolupat produeix un pols elèctric amb una amplitud de 12 V, un temps d'augment de 112 ps i un ample de pols (FWHM) de 155 ps. Amb l'objectiu d'augmentar l'amplitud dels polsos, s'han proposat dues tècniques útils en aquest treball. El primer consisteix a afegir dos generadors de forma paral·lela, en aquest disseny proposat, cal tenir en compte algunes especificacions per a fer la viabilitat d'aquest circuit. No obstant això, la segona tècnica adoptada en aquest treball consisteix en una doble etapa de generadors, ambdues tècniques donen lloc a una bona actuació; en lloc d'un únic mòdul d'un generador de pols, les tècniques proposades en aquest treball augmenten l'amplitud al voltant del doble. Per transmetre i rebre polsos ultra-curts generats, s'han utilitzat dos tipus diferents d'antenes UWB. En primer lloc, una antena de Vivaldi amb un ample de banda d'uns 5,5 GHz de 600 MHz a 6 GHz. Mentre que la segona és una antena Vivaldi amb un ample de banda de 6 GHz de 400 MHz a 6.2 GHz. Mitjançant el sensor de radar ultra-ampla desenvolupat, es va realitzar la mesura de la prova. Incloïen propietats elèctriques i mesures de distància a les plaques metàl·liques, fusta i PVC. S'ha trobat que la incertesa del sensor de radar és de 14 mm (dades mesurades espantades entre + 14 mm per a un objectiu fix). El disseny i la implementació real condueixen a aconseguir un excel·lent prototip de rendiment per a una aplicació no destructiva.[EN] Due to the relevance of application fields of ultra-wideband radar sensor, and also the requirement of each specific application, there is an increasing demand of compact, low cost and high accuracy design of ultra-wideband radar sensor. With a view to addressing these demands, this thesis aims to propose an advanced UWB radar sensor. This research work deals with the design of the ultra-wideband (UWB) radar sensor for non-destructive (NDT) application. The design details include the design of ultra-short, high power pulse generator monocycle pulse with a minimum of ringing. The developed radar was build in bi-static configuration. The goal of this work is to measure the distance range and electrical properties of a target e.g, metal and dielectric materials, such as Polyvinyl chloride (PV C). To achieve this goal, a novel ultrashort, high power pulse generator (radar pulser) has been developed. The new pulse generator consists of a transistor operating in avalanche mode and a pulse sharpening circuit using a new model of step recovery diode (SRD). In order to converts the Gaussian pulse to a monocycle, a monocycle forming network (MFN) has been added. The developed pulse generator produces an electrical pulse with an amplitude of 12 V, a rise-time of 112 ps and pulse width (FWHM) of 155 ps. For the purpose to increase the amplitude of the pulses, two useful techniques have been proposed in this work. The first one consist of adding two generators in parallel, in this proposed design some specification was be taking into account to making the workability of this circuit. However, the second technic adopted in this work consists of a two-stage of generators, both technics give rise to a good performance; instead of a single module of a pulse generator, the techniques proposed in this work increase the amplitude around the double. In order to transmit and receive the generated ultra-short pulses, two different types of UWB antennas have been used. First, a Vivaldi antenna with a bandwidth of about 5.5 GHz from 600 MHz to 6 GHz. While the second is a Vivaldi antenna with a bandwidth of 6 GHz from 400 Mhz to 6,2 GHz. Using the developed ultra-wideband radar sensor, test measurement was performed. These included electrical properties as well as distance measurement towards metal plates, wood, and PVC. The uncertainty of the radar sensor has been found to be 14 mm (measured data scared within + 14 mm for a fixed target). The design and real implementation leading to achieve excellent performance prototype for a non-destructive application.Ahajjam, Y. (2019). Design and Implementation of a UWB Radar Sensor for Non-Destructive Application [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/124057TESI

Multistatic radar optimization for radar sensor network applications

The design of radar sensor networks (RSN) has undergone great advancements in recent years. In fact, this kind of system is characterized by a high degree of design flexibility due to the multiplicity of radar nodes and data fusion approaches. This thesis focuses on the development and analysis of RSN architectures to optimize target detection and positioning performances. A special focus is placed upon distributed (statistical) multiple-input multipleoutput (MIMO) RSN systems, where spatial diversity could be leveraged to enhance radar target detection capabilities. In the first part of this thesis, the spatial diversity is leveraged in conjunction with cognitive waveform selection and design techniques to quickly adapt to target scene variations in real time. In the second part, we investigate the impact of RSN geometry, particularly the placement of multistatic radar receivers, on target positioning accuracy. We develop a framework based on cognitive waveform selection in conjunction with adaptive receiver placement strategy to cope with time-varying target scattering characteristics and clutter distribution parameters in the dynamic radar scene. The proposed approach yields better target detection performance and positioning accuracy as compared with conventional methods based on static transmission or stationary multistatic radar topology. The third part of this thesis examines joint radar and communication systems coexistence and operation via two possible architectures. In the first one, several communication nodes in a network operate separately in frequency. Each node leverages the multi-look diversity of the distributed system by activating radar processing on multiple received bistatic streams at each node level in addition to the pre-existing monostatic processing. This architecture is based on the fact that the communication signal, such as the Orthogonal Frequency Division Multiplexing (OFDM) waveform, could be well-suited for radar tasks if the proper waveform parameters are chosen so as to simultaneously perform communication and radar tasks. The advantage of using a joint waveform for both applications is a permanent availability of radar and communication functions via a better use of the occupied spectrum inside the same joint hardware platform. We then examine the second main architecture, which is more complex and deals with separate radar and communication entities with a partial or total spectrum sharing constraint. We investigate the optimum placement of radar receivers for better target positioning accuracy while reducing the radar measurement errors by minimizing the interference caused by simultaneous operation of the communication system. Better performance in terms of communication interference handling and suppression at the radar level, were obtained with the proposed placement approach of radar receivers compared to the geometric dilution of precision (GDOP)-only minimization metric

Modulation and Multiple Access Techniques for Ultra-Wideband Communication Systems

Two new energy detection (ED) Ultra-Wideband (UWB) systems are proposed in this dissertation. The first one is an ED UWB system based on pulse width modulation (PWM). The bit error rate (BER) performance of this ED PWM system is slightly worse than ED pulse position modulation (PPM) system in additive white Gaussian noise (AWGN) channels. However, the BER performance of this ED PWM system surpasses that of a PPM system in multipath channels since a PWM system does not suffer cross-modulation interference (CMI) as a PPM system. In the presence of synchronization errors, the BER performance of a PWM system also surpasses that of a PPM system. The second proposed ED UWB system is based on using two pulses, which are the different-order derivatives of the Gaussian pulse, to transmitted bit 0 or 1. These pulses are appropriately chosen to separate their spectra in frequency domain.The receiver is composed of two energy detection branches and each branch has a filter which captures the signal energy of either bit 0 or 1. The outputs of two branches are subtracted from each other to generate the decision statistic and the value of this statistic is compared to a threshold to determine the transmitted bits. This system is named as acf{GFSK} system in this dissertation and it exhibits the same BER performance as a PPM system in AWGN channels. In multipath channels, a GFSK system surpasses a PPM system because it does not suffer CMI. And the BER performance of a GFSK system is better than a PPM system in the presence of synchronization errors. When a GFSK system is compared to a PWM system, it will always achieve approximately 2 dB improvement in AWGN channels, multipath channels, and in the presence synchronization errors. However, a PWM system uses lower-order derivatives of the Gaussian pulse to transmit signal, and this leads to a simple pulse generator. In this dissertation, an optimal threshold is applied to improve PPM system performance. The research results show that the application of an optimal threshold can e

Modulation and Multiple Access Techniques for Ultra-Wideband Communication Systems

Two new energy detection (ED) Ultra-Wideband (UWB) systems are proposed in this dissertation. The first one is an ED UWB system based on pulse width modulation (PWM). The bit error rate (BER) performance of this ED PWM system is slightly worse than ED pulse position modulation (PPM) system in additive white Gaussian noise (AWGN) channels. However, the BER performance of this ED PWM system surpasses that of a PPM system in multipath channels since a PWM system does not suffer cross-modulation interference (CMI) as a PPM system. In the presence of synchronization errors, the BER performance of a PWM system also surpasses that of a PPM system. The second proposed ED UWB system is based on using two pulses, which are the different-order derivatives of the Gaussian pulse, to transmitted bit 0 or 1. These pulses are appropriately chosen to separate their spectra in frequency domain.The receiver is composed of two energy detection branches and each branch has a filter which captures the signal energy of either bit 0 or 1. The outputs of two branches are subtracted from each other to generate the decision statistic and the value of this statistic is compared to a threshold to determine the transmitted bits. This system is named as acf{GFSK} system in this dissertation and it exhibits the same BER performance as a PPM system in AWGN channels. In multipath channels, a GFSK system surpasses a PPM system because it does not suffer CMI. And the BER performance of a GFSK system is better than a PPM system in the presence of synchronization errors. When a GFSK system is compared to a PWM system, it will always achieve approximately 2 dB improvement in AWGN channels, multipath channels, and in the presence synchronization errors. However, a PWM system uses lower-order derivatives of the Gaussian pulse to transmit signal, and this leads to a simple pulse generator. In this dissertation, an optimal threshold is applied to improve PPM system performance. The research results show that the application of an optimal threshold can e