Multiple Solutions Starting from Real Shaped Beams in Equispaced Linear Arrays

In the present work, the theoretical basis of the multiplicity of solutions obtained from an initial real symmetric distribution is derived. This initial solution is devoted to generating an equivalent pure real shaped-beam pattern for a concrete synthesis scenario. However, these new solutions are not based on real symmetric distributions; hence, not based on the generation of pure real patterns. The bandwidth performances and tolerance to errors provided by the multiple solutions in the array design are analyzed by considering different architectures, also including mutual coupling models and element factor expressions due to accuracy purposes. In addition, a technique to obtain efficient linear arrays by designing resonant structures is addressed. Examples involving both standard linear arrays of half-wavelength cylindrical dipoles and resonant linear arrays generating flat-top beam patterns are reported and discussed. Additionally, an extension to planar arrays performed by means of a generalisation of the Baklanov transformation through collapsed distribution techniques inspired in the well-known method devised by Tseng and Cheng is performed. In such a way, an analysis of the quality of solutions for generating circular and elliptical footprints with controlled both SLL and ripple which are highly interesting in the framework of space vehicle applicationsThis work was supported in part by the FEDER/Ministerio de Ciencia, Innovación y Universidades-Agencia Estatal de Investigación under Project TEC2017-86110-R. The work of A.Á.S.-S. is supported by the Xunta de Galicia Postdoctoral Fellowship with reference ED481B 2018/008S

Study and applications of retrodirective and self adaptive electromagnetic-wave phase controls to a Mars probe

Computer analyses of retrodirective, and self adaptive antenna phase control techniques for Mars prob

MVDR broadband beamforming using polynomial matrix techniques

This thesis addresses the formulation of and solution to broadband minimum variance distortionless response (MVDR) beamforming. Two approaches to this problem are considered, namely, generalised sidelobe canceller (GSC) and Capon beamformers. These are examined based on a novel technique which relies on polynomial matrix formulations. The new scheme is based on the second order statistics of the array sensor measurements in order to estimate a space-time covariance matrix. The beamforming problem can be formulated based on this space-time covariance matrix. Akin to the narrowband problem, where an optimum solution can be derived from the eigenvalue decomposition (EVD) of a constant covariance matrix, this utility is here extended to the broadband case. The decoupling of the space-time covariance matrix in this case is provided by means of a polynomial matrix EVD. The proposed approach is initially exploited to design a GSC beamformer for a uniform linear array, and then extended to the constrained MVDR, or Capon, beamformer and also the GSC with an arbitrary array structure. The uniqueness of the designed GSC comes from utilising the polynomial matrix technique, and its ability to steer the array beam towards an off-broadside direction without the pre-steering stage that is associated with conventional approaches to broadband beamformers. To solve the broadband beamforming problem, this thesis addresses a number of additional tools. A first one is the accurate construction of both the steering vectors based on fractional delay filters, which are required for the broadband constraint formulation of a beamformer, as for the construction of the quiescent beamformer. In the GSC case, we also discuss how a block matrix can be obtained, and introduce a novel paraunitary matrix completion algorithm. For the Capon beamformer, the polynomial extension requires the inversion of a polynomial matrix, for which a residue-based method is proposed that offers better accuracy compared to previously utilised approaches. These proposed polynomial matrix techniques are evaluated in a number of simulations. The results show that the polynomial broadband beamformer (PBBF) steersthe main beam towards the direction of the signal of interest (SoI) and protects the signal over the specified bandwidth, and at the same time suppresses unwanted signals by placing nulls in their directions. In addition to that, the PBBF is compared to the standard time domain broadband beamformer in terms of their mean square error performance, beam-pattern, and computation complexity. This comparison shows that the PBBF can offer a significant reduction in computation complexity compared to its standard counterpart. Overall, the main benefits of this approach include beam steering towards an arbitrary look direction with no need for pre-steering step, and a potentially significant reduction in computational complexity due to the decoupling of dependencies of the quiescent beamformer, blocking matrix, and the adaptive filter compared to a standard broadband beamformer implementation.This thesis addresses the formulation of and solution to broadband minimum variance distortionless response (MVDR) beamforming. Two approaches to this problem are considered, namely, generalised sidelobe canceller (GSC) and Capon beamformers. These are examined based on a novel technique which relies on polynomial matrix formulations. The new scheme is based on the second order statistics of the array sensor measurements in order to estimate a space-time covariance matrix. The beamforming problem can be formulated based on this space-time covariance matrix. Akin to the narrowband problem, where an optimum solution can be derived from the eigenvalue decomposition (EVD) of a constant covariance matrix, this utility is here extended to the broadband case. The decoupling of the space-time covariance matrix in this case is provided by means of a polynomial matrix EVD. The proposed approach is initially exploited to design a GSC beamformer for a uniform linear array, and then extended to the constrained MVDR, or Capon, beamformer and also the GSC with an arbitrary array structure. The uniqueness of the designed GSC comes from utilising the polynomial matrix technique, and its ability to steer the array beam towards an off-broadside direction without the pre-steering stage that is associated with conventional approaches to broadband beamformers. To solve the broadband beamforming problem, this thesis addresses a number of additional tools. A first one is the accurate construction of both the steering vectors based on fractional delay filters, which are required for the broadband constraint formulation of a beamformer, as for the construction of the quiescent beamformer. In the GSC case, we also discuss how a block matrix can be obtained, and introduce a novel paraunitary matrix completion algorithm. For the Capon beamformer, the polynomial extension requires the inversion of a polynomial matrix, for which a residue-based method is proposed that offers better accuracy compared to previously utilised approaches. These proposed polynomial matrix techniques are evaluated in a number of simulations. The results show that the polynomial broadband beamformer (PBBF) steersthe main beam towards the direction of the signal of interest (SoI) and protects the signal over the specified bandwidth, and at the same time suppresses unwanted signals by placing nulls in their directions. In addition to that, the PBBF is compared to the standard time domain broadband beamformer in terms of their mean square error performance, beam-pattern, and computation complexity. This comparison shows that the PBBF can offer a significant reduction in computation complexity compared to its standard counterpart. Overall, the main benefits of this approach include beam steering towards an arbitrary look direction with no need for pre-steering step, and a potentially significant reduction in computational complexity due to the decoupling of dependencies of the quiescent beamformer, blocking matrix, and the adaptive filter compared to a standard broadband beamformer implementation

Synthetic Aperture Digital Beamsteering Array for Global Positioning System Interference Mitigation: A Study on Array Topology

The Global Positioning System (GPS) satellite navigation system is deeply intertwined with civilian everyday life. Unfortunately for the civilians that use the system, the GPS system is vulnerable to external interference. Antenna arrays with Direction of Arrival (DoA) signal identification and beamsteering provide a very effective technique for mitigating directional interference by moving the antenna gain toward the Signal of Interest (SOI) or away from the Signal not of Interest (SNOI), however, such systems are typically too large to integrate or require more processing capabilities than civilian devices are able to provide. Synthetic aperture arrays are a means to reduce the array size but provide a similar interference protection with a smaller processing capability overhead. This thesis assists in array selection by providing simulated gains of different switched antenna arrays. The Uniform Circular Array (UCA), rectangular array, random array, random full aperture, random sequential, ring (UCA random hybrid) topologies are evaluated. In a pure synthetic beamsteering system in the presence of continuous wave (CW) interference, it is determined that array topology has marginal impact on Signal to Interference Noise Ratio (SINR) as each array's results show very similar performance. With the two CW scenarios in the absence of null steering, the UCA maintains the highest performance using the smallest number of antenna elements

Study of shuttle imaging microwave system antenna. Volume 1: Conceptual design

A detailed preliminary design and complete performance evaluation are presented of an 11-channel large aperture scanning radiometer antenna for the shuttle imaging microwave system (SIMS) program. Provisions for interfacing the antenna with the space shuttle orbiter are presented and discussed. A program plan for hardware development and a rough order of magnitude (ROM) cost are also included. The conceptual design of the antenna is presented. It consists of a four-meter diameter parabolic torus main reflector, which is a graphite/epoxy shell supported by a graphite/epoxy truss. A rotating feed wheel assembly supports six Gregorian subreflectors covering the upper eight frequency channels from 6.6 GHz through 118.7 GHz, and two three-channel prime forms feed assemblies for 0.6, 1.4, and 2.7 GHz. The feed wheel assembly also holds the radiometers and power supplies, and a drive system using a 400 Hz synchronous motor is described. The RF analysis of the antenna is performed using physical optics procedures for both the dual reflector Gregorian concept and the single reflector prime focus concept. A unique aberration correcting feed for 2.7 GHz is analyzed. A structural analysis is also included. The analyses indicate that the antenna will meet system requirements

Advanced array processing techniques and systems

Research and development on smart antennas, which are recognized as a promising technique to improve the performance of mobile communications, have been extensive in the recent years. Smart antennas combine multiple antenna elements with a signal processing capability in both space and time to optimize its radiation and reception pattern automatically in response to the signal environment. This paper concentrates on the signal processing aspects of smart antenna systems. Smart antennas are often classified as either switched-beam or adaptive-array systems, for which a variety of algorithms have been developed to enhance the signal of interest and reject the interference. The antenna systems need to differentiate the desired signal from the interference, and normally requires either a priori knowledge or the signal direction to achieve its goal. There exists a variety of methods for direction of arrival (DOA) estimation with conflicting demands of accuracy and computation. Similarly, there are many algorithms to compute array weights to direct the maximum radiation of the array pattern toward the signal and place nulls toward the interference, each with its convergence property and computational complexity. This paper discusses some of the typical algorithms for DOA estimation and beamforming. The concept and details of each algorithm are provided. Smart antennas can significantly help in improving the performance of communication systems by increasing channel capacity and spectrum efficiency, extending range coverage, multiplexing channels with spatial division multiple access (SDMA), and compensating electronically for aperture distortion. They also reduce delay spread, multipath fading, co-channel interference, system complexity, bit error rates, and outage probability. In addition, smart antennas can locate mobile units or assist the location determination through DOA and range estimation. This capability can support and benefit many location-based services including emergency assistance, tracking services, safety services, billing services, and information services such as navigation, weather, traffic, and directory assistance

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

Design strategies for electrically small antennas, actively matched with non-foster elements

Mención Internacional en el título de doctorDuring the last years, some researchers have been working on active matching or on non-Foster matching networks for electrically small antennas (ESAs), in response to the vertiginous increase in demand for compact devices working in multiband platforms. The inclusion of non- Foster networks allows broad bandwidths at lower frequencies, overcoming the inherent limitations derived from the high-quality factor (Q) property of ESAs. Thus, the development of multiband antennas with an engineered lower broadband obtained by embedding an active non- Foster matching network (MN) is one of the primary objectives addressed in this work. Such non-Foster MNs are implemented by using Negative Impedance Converters (NICs), introduced many years ago to realize negative capacitors or negative inductors that disobey the Foster's reactance theorem. In this sense, an integral design methodology of actively matched ESAs with embedded non-Foster elements is proposed and developed. This design method takes into account the operating parameters inherent to a radiating element, such as efficiency and radiation pattern, impedance matching, realizability, and stability. A new parameter (called Sens) on the sensitivity of the ESA when loaded with a non-Foster form is introduced. This sensitivity analysis will allow us to choose not only the kind of antennas that can be properly matched with non-Foster networks but also the most suitable position of such networks into the antenna structure, in order to optimize the performance of the design. The design methodology can be easily extended to any type of antenna, disregarding its electrical size. Two electrically small antennas are presented as design examples in which the proposed design strategy is applied. First, a printed small semiloop antenna, which is resonant at 1200 MHz, is loaded with an embedded MOSFET-based NIC, resulting in a new lower-band with a fractional bandwidth (FBW) of 119% (centered at 117 MHz). Second, a blade-type monopole, whose resonant frequency is around 300 MHz, is loaded with an embedded non-Foster MN, resulting in a new working band whose FBW of 82% (centered at 85 MHz). The notable results in terms of impedance bandwidth and miniaturization level encouraged us to keep seeking for solutions for radiation pattern changes and added noise issues. Finally, the proposed design strategy is applied to fewelement antenna arrays to obtain a multiband performance, keeping unchanged the natural response of the host structure (i.e. around its resonant frequency).Durante los últimos años, algunos investigadores han venido trabajando en la inclusión de redes de adaptación tipo non-Foster en antenas eléctricamente pequeñas (Electrically Small Antennas, ESA). Esto en respuesta a la creciente demanda de dispositivos compactos, que funcionen a diferentes bandas de frecuencia, como parte de los modernos sistemas y plataformas multibanda. La consecución de sistemas compactos y de banda ancha, así como la obtención de múltiples frecuencias de trabajo han sido uno de los objetivos primarios de la presente tesis doctoral. La inclusión de estructuras non-Foster, que reciben este nombre debido a que no obedecen a las propiedades establecidas por el teorema de R. M. Foster en 1924, permite el ensanchamiento de la banda de adaptación de impedancia o la obtención de una banda adicional para una misma estructura radiante. Dentro de los circuitos más representativos de las redes non-Foster se encuentran los Convertidores de Impedancia Negativa (Negative Impedance Converter, NIC), comúnmente implementados con transistores, a través de los cuales es posible la implementación de inductores o de condensadores “negativos”. La realización de una impedancia “negativa” por medio de un NIC, es de vital importancia en la adaptación de la impedancia de antena en banda ancha que se busca en este trabajo. En este sentido, se hace necesario establecer una metodología de diseño de este tipo de antenas, que tenga en cuenta los parámetros de funcionamiento inherentes a un elemento radiante, como son: eficiencia y diagrama de radiación, adaptación de impedancias, factibilidad y estabilidad. Esto, a través del análisis de la sensibilidad a la ubicación de puertos (propuesto en este proyecto), análisis de estabilidad del sistema completo (antena y red de adaptación activa), análisis de distribución de corrientes etc., hace que la estrategia de diseño que se pretende desarrollar y describir pueda resultar una herramienta realmente útil en el diseño de las mencionadas antenas. El parámetro de sensibilidad, Sens, introducido en este trabajo, otorga al diseñador un criterio de selección cuantitativo con respecto a qué tipo de antena puede, en efecto, ser adaptada con elementos non-Foster y la posición misma de _estos dentro de la estructura. De este modo, el parámetro Sens constituye una herramienta de optimización del desempeño del sistema radiante diseñado. Adicionalmente, cabe mencionar que la metodología de diseño propuesta y desarrollada en esta tesis puede ser aplicada a cualquier tipo de antena, sin importar su naturaleza ni su tamaño en términos eléctricos. Luego de desarrollada y descrita la metodología |estrategia| de diseño, se presentan dos antenas eléctricamente pequeñas a manera de ejemplos de diseño. La primera consiste en un semilazo impreso sobre un dieléctrico, resonante a 1200 MHz, cargado con un NIC compuesto de transistores MOSFET. Como resultado, se obtiene una nueva banda de trabajo cuyo ancho de banda de adaptación relativo (FBW) es de 119% (centrado en 117 MHz). La segunda antena ejemplo consiste en un monopolo ensanchado, tipo aleta (blade-monopole), en cuya estructura es embebida una red de adaptación activa, basada también en transistores MOSFET. En este segundo caso, se obtuvo una banda adicional con un FBW de 82% (centrado en 85 MHz). Los notables resultados en términos de adaptación de impedancia y de nivel de miniaturización de las estructuras radiantes, alentaron al autor a continuar con la búsqueda de alternativas de solución a los cambios en el diagrama de radiación observados y a el nivel de ruido adicionado por la red activa embebida. Finalmente, la estrategia de diseño descrita es aplicada a arreglos (arrays) de antenas de pocos elementos, en busca de obtener un comportamiento multibanda en el que la banda incluida comprenda frecuencias a las que toda la estructura es eléctricamente pequeña.Programa Oficial de Doctorado en Multimedia y ComunicacionesPresidente: Milos Mazánek.- Secretario: Luis Enrique García Muñoz.- Vocal: Marco A. Antoniade

Ultra-Wideband Array Antennas

Wireless communication has become an indispensable part of modern life. One of the mostimportant components of wireless communication systems are antennas, termed as "eyes" and "ears" of communication systems. A printed antenna, one of the most commercial antennas, is widely used for civil and military applications, i.e., for communication systems, radar systems, satellite and transportation systems since the printed antenna provides some benefits such as light weight, compact structure and low manufacturing cost. A printed antenna design for a communication technology called Ultra-Wide Band (UWB) is discussed in this dissertation. Ultra-Wide Band communication has undergone intensive investigation in the past decade since the Federal Communications Commission (FCC) released the free license spectral mask operation of the UWB radio over 7.5 GHz bandwidth from 3.1 to 10.6 GHz (UWB frequency range), a technology promising high-rate data transmission over a short range. On the other hand, a UWB communication system requires extremely low radiation power to avoid interferences to other communication systems. As an answer for this challenge, three strategies based on antenna aspects are proposed in the frame of this work. The first strategy is to design a compact and directive single radiator. The printed monopole antenna was selected as the radiator, in particular the printed circular monopole antenna (PCMA), was reinvestigated and modified as a directive PCMA. Secondly, a UWB array antenna employing the directive PCMA element was designed to focus the radiation toward a certain direction. Some matching techniques were combined in the design to achieve impedance matching over the UWB frequency range. The measurement result of the antenna under test showed a focused radiation pattern and the impedance matching better than -10 dB was achieved for the whole frequency band. The concept of frequency invariant beam pattern antenna arrays is applied as the third strategy. The concept, adopted from the broadband sensor’s theory for acoustic purpose, is applied to the microwave frame. Based on this concept, a prototype of the PCMA array fed by a set of low pass filters was realized in planar technology at the first time to achieve frequency invariant beam patterns. The measurement of the fabricated antenna showed that the beamwidth can be kept constant over the whole frequency band