Investigation of Non-coherent Discrete Target Range Estimation Techniques for High-precision Location

Ranging is an essential and crucial task for radar systems. How to solve the range-detection problem effectively and precisely is massively important. Meanwhile, unambiguity and high resolution are the points of interest as well. Coherent and non-coherent techniques can be applied to achieve range estimation, and both of them have advantages and disadvantages. Coherent estimates offer higher precision but are more vulnerable to noise and clutter and phase wrap errors, particularly in a complex or harsh environment, while the non-coherent approaches are simpler but provide lower precision. With the purpose of mitigating inaccuracy and perturbation in range estimation, miscellaneous techniques are employed to achieve optimally precise detection. Numerous elegant processing solutions stemming from non-coherent estimate are now introduced into the coherent realm, and vice versa. This thesis describes two non-coherent ranging estimate techniques with novel algorithms to mitigate the instinct deficit of non-coherent ranging approaches. One technique is based on peak detection and realised by Kth-order Polynomial Interpolation, while another is based on Z-transform and realised by Most-likelihood Chirp Z-transform. A two-stage approach for the fine ranging estimate is applied to the Discrete Fourier transform domain of both algorithms. An N-point Discrete Fourier transform is implemented to attain a coarse estimation; an accurate process around the point of interest determined in the first stage is conducted. For KPI technique, it interpolates around the peak of Discrete Fourier transform profiles of the chirp signal to achieve accurate interpolation and optimum precision. For Most-likelihood Chirp Z-transform technique, the Chirp Z-transform accurately implements the periodogram where only a narrow band spectrum is processed. Furthermore, the concept of most-likelihood estimator is introduced to combine with Chirp Z-transform to acquire better ranging performance. Cramer-Rao lower bound is presented to evaluate the performance of these two techniques from the perspective of statistical signal processing. Mathematical derivation, simulation modelling, theoretical analysis and experimental validation are conducted to assess technique performance. Further research will be pushed forward to algorithm optimisation and system development of a location system using non-coherent techniques and make a comparison to a coherent approach

Design and fabrication of customized fiber gratings to improve the interrogation of optical fiber sensors

[EN] Fiber grating sensors and devices have demonstrated outstanding capabilities in both telecommunications and sensing areas, due to their well-known advantageous characteristics. Therefore, one of the most important motivations lies in the potential of customized fiber gratings to be suitably employed for improving the interrogation process of optical fiber sensors and systems. This Ph.D. dissertation is focused on the study, design, fabrication and performance evaluation of customized fiber Bragg gratings (FBGs) and long period gratings (LPGs) with the double aim to present novel sensing technologies and to enhance the response of existing sensing systems. In this context, a technique based on time-frequency domain analysis has been studied and applied to interrogate different kind of FBGs-based sensors. The distribution of the central wavelength along the sensing structures has been demonstrated, based on a combination of frequency scanning of the interrogating optical pulse and optical time-domain reflectometry (OTDR), allowing the detection of spot events with good performance in terms of measurand resolution. Moreover, different customized FBGs have been interrogated using a technology inspired on the operation principle of microwave photonics (MWP) filters, enabling the detection of spot events using radio-frequency (RF) devices with modest bandwidth. The sensing capability of these technological platforms has been fruitfully employed for implementing a large scale quasi-distributed sensor, based on an array of cascaded FBGs. The potentiality of LPGs as fiber optic sensors has also been investigated in a new fashion, exploiting the potentials of MWP filtering techniques. Besides, a novel approach for simultaneous measurements based on a half-coated LPG has been proposed and demonstrated. Finally, the feasibility of FBGs as selective wavelength filters has been exploited in sensing applications; an alternative approach to improve the response and performance of Brillouin distributed fiber sensors has been studied and validated via experiments. The performance of the reported sensing platforms have been analyzed and evaluated so as to characterize their impact on the fiber sensing field and to ultimately identify the use of the most suitable technology depending on the processing task to be carried out and on the final goal to reach.[ES] Los sensores y dispositivos en fibra basados en redes de difracción han mostrado excepcionales capacidades en el ámbito de las telecomunicaciones y del sensado, gracias a sus excelentes propiedades. Entre las motivaciones más estimulantes destaca la posibilidad de fabricar redes de difracción ad-hoc para implementar y/o mejorar las prestaciones de los sensores fotónicos. Esta tesis doctoral se ha enfocado en el estudio, diseño, fabricación y evaluación de las prestaciones de redes de difracción de Bragg (FBGs) y de redes de difracción de periodo largo (LPGs) personalizadas con el fin de desarrollar nuevas plataformas de detección y a la vez mejorar la respuesta y las prestaciones de los sensores fotónicos ya existentes. En este contexto, una técnica basada en el análisis tiempofrecuencia se ha estudiado e implementado para la interrogación de sensores en fibra basados en varios tipos y modelos de FBGs. Se ha analizado la distribución de la longitud de onda central a lo largo de la estructura de sensado, gracias a una metodología que conlleva el escaneo en frecuencia del pulso óptico incidente y la técnica conocida como reflectometria óptica en el dominio del tiempo (OTDR). De esta manera se ha llevado a cabo la detección de eventos puntuales, alcanzando muy buenas prestaciones en términos de resolución de la magnitud a medir. Además, se han interrogado varias FBGs a través de una técnica basada en el principio de operación de los filtros de fotónica de microondas (MWP), logrando así la detección de eventos puntuales usando dispositivos de radio-frecuencia (RF) caracterizados por un moderado ancho de banda. La capacidad de sensado de estas plataformas tecnológicas ha sido aprovechada para la realización de un sensor quasi-distribuido de gran alcance, formado por una estructura en cascada de muchas FBGs. Por otro lado, se han puesto a prueba las capacidades de las LPGs como sensores ópticos según un enfoque novedoso; para ello se han aprovechados las potencialidades de los filtros de MWP. Asimismo, se ha estudiado y demostrado un nuevo método para medidas simultáneas de dos parámetros, basado en una LPG parcialmente recubierta por una película polimérica. Finalmente, se ha explotado la viabilidad de las FBGs en cuanto al filtrado selectivo en longitud de onda para aplicaciones de sensado; para ello se ha propuesto un sistema alternativo para la mejora de la respuesta y de las prestaciones de sensores ópticos distribuidos basados en el scattering de Brillouin. En conclusión, se han analizado y evaluado las prestaciones de las plataformas de sensado propuestas para caracterizar su impacto en el ámbito de los sistemas de detección por fibra y además identificar el uso de la tecnología más adecuada dependiendo de la tarea a desarrollar y del objetivo a alcanzar.[CA] Els sensors i dispositius en fibra basats en xarxes de difracció han mostrat excepcionals capacitats en l'àmbit de les telecomunicacions i del sensat, gràcies a les seus excel¿lents propietats. Entre les motivacions més estimulants destaca la possibilitat de fabricar xarxes de difracció ad-hoc per a implementar i/o millorar les prestacions de sensors fotònics. Esta tesi doctoral s'ha enfocat en l'estudi, disseny, fabricació i avaluació de les prestacions de xarxes de difracció de Bragg (FBGs) i de xarxes de difracció de període llarg (LPGs) personalitzades per tal de desenvolupar noves plataformes de detecció i al mateix temps millorar la resposta i les prestacions dels sensors fotònics ja existents. En este context, una tècnica basada en l'anàlisi temps-freqüència s'ha estudiat i implementat per a la interrogació de sensors en fibra basats en diversos tipus i models de FBGs. S'ha analitzat la distribució de la longitud d'ona central al llarg de l'estructura de sensat, gràcies a una metodologia que comporta l'escaneig en freqüència del pols òptic incident i la tècnica coneguda com reflectometria òptica en el domini del temps (OTDR). D'esta manera s'ha dut a terme la detecció d'esdeveniments puntuals, aconseguint molt bones prestacions en termes de resolució de la magnitud a mesurar. A més, s'han interrogat diverses FBGs a través d'una tècnica basada en el principi d'operació dels filtres de fotònica de microones (MWP), aconseguint així la detecció d'esdeveniments puntuals utilitzant dispositius de ràdio-freqüència (RF) caracteritzats per un moderat ample de banda. La capacitat de sensat d'aquestes plataformes tecnològiques ha sigut aprofitada per a la realització d'un sensor quasi-distribuït a llarga escala, format per una estructura en cascada de moltes FBGs. D'altra banda, s'han posat a prova les capacitats de les LPGs com a sensors òptics segons un enfocament nou; per a això s'han aprofitat les potencialitats dels filtres de MWP. Així mateix, s'ha estudiat i demostrat un nou mètode per a mesures simultànies de dos paràmetres, basat en una LPG parcialment recoberta per una pel¿lícula polimèrica. Finalment, s'ha explotat la viabilitat de les FBGs pel que fa al filtrat selectiu en longitud d'ona per a aplicacions de sensat; per això s'ha proposat un sistema alternatiu per a la millora de la resposta i de les prestacions de sensors òptics distribuïts basats en el scattering de Brillouin. S'han analitzat i avaluat les prestacions de les plataformes de sensat propostes per a caracteritzar el seu impacte en l'àmbit dels sistemes de detecció per fibra i a més identificar l'ús de la tecnologia més adequada depenent de la tasca a desenvolupar i de l'objectiu a assolir.Ricchiuti, AL. (2016). Design and fabrication of customized fiber gratings to improve the interrogation of optical fiber sensors [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/66343TESISPremiad

Ultra Wideband

Ultra wideband (UWB) has advanced and merged as a technology, and many more people are aware of the potential for this exciting technology. The current UWB field is changing rapidly with new techniques and ideas where several issues are involved in developing the systems. Among UWB system design, the UWB RF transceiver and UWB antenna are the key components. Recently, a considerable amount of researches has been devoted to the development of the UWB RF transceiver and antenna for its enabling high data transmission rates and low power consumption. Our book attempts to present current and emerging trends in-research and development of UWB systems as well as future expectations

Modulated Microwave Retro-reflectors and Their Applications

This work seeks to investigate the viability of establishing communications links using modulated microwave reflectors, and explores potential application areas. A primary and underlying objective has been to combine modulation of radar cross section (RCS) with the wide-angle RCS response of a microwave retro-reflector so as to yield a transponder which imparts information content on the reflected spectrum. Since the RCS is electrically large, the communications link is directive and yet the transponder is not a transmitter of microwave energy and hence has modest power needs. The microwave retro-array was quickly identified as the most promising structure to achieve these aims, and hence the further objectives of the work have been to investigate this structure and fabricate working prototypes so as to: • achieve a manufacturable structure. • perform measurements to compare with theoretical models of behaviour. • explore the limits of performance, and seek to expand them. • identify applications and markets. • explore and pursue such related discoveries that may occur. All the above aims have been explored to some extent, and the findings have been reported in the body of the thesis. The background and historical context is discussed in chapter 1, while chapter 2 reports on the construction and characterisation of 16- element modulated retro-array prototypes operating at a 2.5 GHz carrier frequency. The applied nature of this work is extended in chapters 3 and 4 to printed integrated circuits for passive transponders, and the scaling of these methods to frequencies around 9.2 GHz. Theoretical models for the properties of much larger arrays are presented in chapter 5, and range finding applications and results presented in chapter 6. Two applications are then discussed for which the required array dimensions are estimated, before closing with conclusions and suggestions for future work

Linearization techniques to suppress optical nonlinearity

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.This thesis is shown the implementation of the linearization techniques such as feedforward and pre-distortion feedback linearization to suppress the optical components nonlinearities caused by the fibre and semiconductor optical amplifier (SOA). The simulation verified these two linearization techniques for single tone direct modulation, two tone indirect modulation and ultra wideband input to the optical fibre. These techniques uses the amplified spontaneously emission (ASE) noise reduction in two loops of SOA by a feed-forward and predistortion linearizer and is shown more than 6dB improvement. Also it investigates linearization for the SOA amplifier to cancel out the third order harmonics or inter-modulation distortion (IMD) or four waves mixing. In this project, more than 20 dB reductions is seen in the spectral re-growth caused by the SOA. Amplifier non-linearity becomes more severe with two strong input channels leading to inter-channel distortion which can completely mask a third adjacent channel. The simulations detailed above were performed utilizing optimum settings for the variable gain, phase and delay components in the error correction loop of the feed forward and Predistortion systems and hence represent the ideal situation of a perfect feed-forward and Predistortion system. Therefore it should be consider that complexity of circuit will increase due to amplitude, phase and delay mismatches in practical design. Also it has describe the compatibility of Software Defined Radio with Hybrid Fibre Radio with simulation model of wired optical networks to be used for future research investigation, based on the star and ring topologies for different modulation schemes, and providing the performance for these configurations

Retroreflector and Multibeam Antenna for a Millimeter Wave Collision Avoidance System

RÉSUMÉ La section efficace du radar (SER) pour des cibles automobiles a une réponse angulaire étroite. Une variation de plusieurs décibels par mètre carré (dBsm) peut également être observée avec un léger changement de l’orientation de la cible. La localisation de telles cibles est difficile pour un radar automobile. En outre, un matériel complexe est généralement nécessaire pour mettre en oeuvre un radar efficace, ce qui se traduit par des systèmes coûteux qui ne sont abordables que dans les véhicules haut de gamme. Cela défie l’objet d’un système de sécurité pour éviter les accidents de la route à grande échelle. Cette thèse présente une nouvelle balise d’amélioration de SER et une antenne multifaisceaux pour des applications de radar automobile. Ces composants peuvent éventuellement améliorer les performances d’un algorithme de super-résolution, et permettre le développement d’un radar d’évitement de collision automobile simple et peu coûteux. Une architecture de système simple et rentable est particulièrement importante dans la gamme de fréquences d’ondes millimétriques, allouée pour cette application, où les atténuations du signal et les coûts de dispositif sont significativement élevés. Les structures proposées dans cette thèse peuvent également trouver des applications dans d’autres applications en ondes millimétriques. Un système radar est analysé en étudiant les propriétés de l’algorithme de super-résolution bien connu ESPRIT. Sur la base d’une simulation numérique MATLAB de cet algorithme, il est établi qu’une SER stable est importante pour l’utilisation de cet algorithme dans des applications automobiles. Ceci peut être réalisé en équipant la cible d’un marqueur d’amélioration de la SER. Deuxièmement, dans cet algorithme, la taille du réseau de récepteurs détermine le nombre de cibles détectables. En sectorisant le CdV du radar en utilisant une antenne multifaisceaux, l’erreur de localisation angulaire peut être réduite pour un plus grand nombre de cibles. La balise proposée est conçue à 77 GHz, fonctionnant dans la bande attribuée au radar automobile (76 GHz à 81 GHz). Les caractéristiques des radars automobiles dans la littérature suggèrent un CdV en forme de faisceau en éventail pour la balise avec un CdV plus large dans le plan azimutal. De CdV de 120o et 9o dans les plans d’azimut et d’élévation sont respectivement choisis comme critères de conception pour la balise proposée. La propriété de rétroréflexion dans le plan d’azimut aide à améliorer la SER de la balise. La balise proposée reflète le signal incident avec une rotation de polarisation linéaire de 90o. Cette modulation de polarisation permet d’améliorer la visibilité de la cible par rapport au bruit de fond. De plus, une modulation d’amplitude est également implémentée dans la balise.----------Rear radar cross section (RCS) of automotive targets has a narrow angular response. A variation of several decibel per square meter (dBsm) can also be observed with slight change in the target orientation. Localization of such targets is challenging for an automotive radar. Furthermore, complex hardware is typically required to implement an effective radar resulting in high-cost systems that are affordable only in high-end vehicles. This defies the object of a safety system to avoid roadside accidents at large scale. This dissertation présents novel RCS enhancing tag and multibeam antenna for automotive radar applications. These components can possibly improve the performance of a super-resolution algorithm, and enable the development of a simple, low-cost automotive collision avoidance radar. Simple and costeffective system architecture is particularly important in millimeter wave frequency range, allocated for this application, where the material losses and device costs are significantly high. The proposed structures in this thesis can also find applications in other millimeter wave applications. A radar system is analyzed by studying the properties of Estimation of Signal Parameters via Rotational Invariance Technique (ESPRIT), a well know super-resolution algorithm. Based on a MATLAB numerical simulation of this algorithm, it is established that a stable target RCS is important for employing this algorithm in automotive applications. This can be achieved by equipping the target with a RCS enhancing tag. Secondly, in this algorithm, the size of the receiver array determines the number of detectable targets. By sectoring the radar field of view (FoV) using a multibeam antenna, the localization error can be reduced for higher number of targets. The proposed tag is designed at 77 GHz, operating in the band allocated for automotive radar (76 GHz to 81 GHz). Automotive radar characteristics in the literature suggest a fan-beam shaped FoV for the tag with wider FoV in azimuth plane. Azimuth and elevation plane FoV of 120o and 9o are selected as design criteria for the proposed tag. Retroreflection property in the azimuth plane helps to improve the tag RCS. The proposed tag reflects the incident signal with 90o linear polarization rotation. This polarization modulation can enhance the target visibility against the background clutter. Additionally, an amplitude modulation is also implemented in the tag. This modulation can help to communicate additional information. It can also facilitate the target detection by improving the signal to noise ratio of the processed received signal

Advanced photon counting techniques for long-range depth imaging

The Time-Correlated Single-Photon Counting (TCSPC) technique has emerged as a candidate approach for Light Detection and Ranging (LiDAR) and active depth imaging applications. The work of this Thesis concentrates on the development and investigation of functional TCSPC-based long-range scanning time-of-flight (TOF) depth imaging systems. Although these systems have several different configurations and functions, all can facilitate depth profiling of remote targets at low light levels and with good surface-to-surface depth resolution. Firstly, a Superconducting Nanowire Single-Photon Detector (SNSPD) and an InGaAs/InP Single-Photon Avalanche Diode (SPAD) module were employed for developing kilometre-range TOF depth imaging systems at wavelengths of ~1550 nm. Secondly, a TOF depth imaging system at a wavelength of 817 nm that incorporated a Complementary Metal-Oxide-Semiconductor (CMOS) 32×32 Si-SPAD detector array was developed. This system was used with structured illumination to examine the potential for covert, eye-safe and high-speed depth imaging. In order to improve the light coupling efficiency onto the detectors, the arrayed CMOS Si-SPAD detector chips were integrated with microlens arrays using flip-chip bonding technology. This approach led to the improvement in the fill factor by up to a factor of 15. Thirdly, a multispectral TCSPC-based full-waveform LiDAR system was developed using a tunable broadband pulsed supercontinuum laser source which can provide simultaneous multispectral illumination, at wavelengths of 531, 570, 670 and ~780 nm. The investigated multispectral reflectance data on a tree was used to provide the determination of physiological parameters as a function of the tree depth profile relating to biomass and foliage photosynthetic efficiency. Fourthly, depth images were estimated using spatial correlation techniques in order to reduce the aggregate number of photon required for depth reconstruction with low error. A depth imaging system was characterised and re-configured to reduce the effects of scintillation due to atmospheric turbulence. In addition, depth images were analysed in terms of spatial and depth resolution

Advances in Optical Amplifiers

Optical amplifiers play a central role in all categories of fibre communications systems and networks. By compensating for the losses exerted by the transmission medium and the components through which the signals pass, they reduce the need for expensive and slow optical-electrical-optical conversion. The photonic gain media, which are normally based on glass- or semiconductor-based waveguides, can amplify many high speed wavelength division multiplexed channels simultaneously. Recent research has also concentrated on wavelength conversion, switching, demultiplexing in the time domain and other enhanced functions. Advances in Optical Amplifiers presents up to date results on amplifier performance, along with explanations of their relevance, from leading researchers in the field. Its chapters cover amplifiers based on rare earth doped fibres and waveguides, stimulated Raman scattering, nonlinear parametric processes and semiconductor media. Wavelength conversion and other enhanced signal processing functions are also considered in depth. This book is targeted at research, development and design engineers from teams in manufacturing industry, academia and telecommunications service operators

A leaky waveguide all-optical analog-to-digital converter

In this thesis we describe a novel all-optical analog-to-digital converter (AOADC) based on a leaky waveguide deflector. The principle of the spatial sampling AOADC is to convert an electrical signal to its corresponding optical deflection angle and then sample and quantize this angle in the spatial domain, instead of the amplitude domain. This AOADC is designed for broadband digital receivers working at frequencies above 20 GHz (a minimum 40 GS/s sampling rate) and provides a resolution higher than 6 bits. An original design based on GRISM (Grating and pRISM) is investigated for a high-resolution ADC implementation; and its challenges have been identified. The investigation provides a general model of spatial sampling AOADCs and highlights their advantages of immunity to optical intensity fluctuation. Later we proposed an AOADC that employs a leaky waveguide structure that is different from any other optical ADC. The AOADC consists of a sampler based on a mode-locked laser and a leaky waveguide deflector driven by traveling wave electrodes, a quantizer based on an integrated optical collector array and broadband photodetectors. These components provide the AOADC with a higher deflection angle and angular resolution resulting in high bit resolution without consuming significant power. The quantization of the deflection angle is done by a simple spatial quantizer that digitizes as well as encodes the signal simultaneously. A detailed design of the E-O deflector and the spatial quantizer has been analyzed and simulated; and some preliminary tests have been conducted. This thesis summarizes our contributions in designing and modeling this novel spatial sampling AOADC.Ph.D., Electrical Engineering -- Drexel University, 200

Linearization techniques to suppress optical nonlinearity

This thesis is shown the implementation of the linearization techniques such as feedforward and pre-distortion feedback linearization to suppress the optical components nonlinearities caused by the fibre and semiconductor optical amplifier (SOA). The simulation verified these two linearization techniques for single tone direct modulation, two tone indirect modulation and ultra wideband input to the optical fibre. These techniques uses the amplified spontaneously emission (ASE) noise reduction in two loops of SOA by a feed-forward and predistortion linearizer and is shown more than 6dB improvement. Also it investigates linearization for the SOA amplifier to cancel out the third order harmonics or inter-modulation distortion (IMD) or four waves mixing. In this project, more than 20 dB reductions is seen in the spectral re-growth caused by the SOA. Amplifier non-linearity becomes more severe with two strong input channels leading to inter-channel distortion which can completely mask a third adjacent channel. The simulations detailed above were performed utilizing optimum settings for the variable gain, phase and delay components in the error correction loop of the feed forward and Predistortion systems and hence represent the ideal situation of a perfect feed-forward and Predistortion system. Therefore it should be consider that complexity of circuit will increase due to amplitude, phase and delay mismatches in practical design. Also it has describe the compatibility of Software Defined Radio with Hybrid Fibre Radio with simulation model of wired optical networks to be used for future research investigation, based on the star and ring topologies for different modulation schemes, and providing the performance for these configurations.EThOS - Electronic Theses Online ServiceGBUnited Kingdo