Modelling and application of a cross-aperture coupled single feed circularly polarised patch antenna

This thesis presents the results of the research that has been carried out in order to design an improved microstrip antenna for a two-way microwave based digital communication link for communication between a road-side unit and a vehicle. The system is to be used for traffic applications such as automatic motorway tolling

Applications of the genetic algorithm optimisation approach in the design of high efficiency microwave class E power amplifiers

In this thesis Genetic Algorithm Optimisation Methods (GA) is studied and for the first time used to design high efficiency microwave class E power amplifiers (PAs) and associated load patch antennas. The difficulties of designing high efficiency PAs is that power transistors are highly non linear and classical design techniques only work for resistive loads. There are currently no high efficient and accurate procedures for design high efficiency PAs. To achieve simplified and accurate design procedure, GA and new design quadratic equations are introduced and applied. The performance analysis is based on linear switch models and non linear circuitry push-pull methods. The results of the analytical calculations and experimental verification showed that the power added efficiency (PAE) of the PAs mainly depend on the losses of the active device itself and are nearly independent on the losses of its harmonic networks. Hence, it has been proven that the cheap material PCB FR4 can be used to design high efficiency class E PAs and it also shown that low Q factor networks have only a minor effect on efficiency, allowing a wide bandwidth to be obtained. In additional, a new procedure for designing class E PAs is introduced and applied. The active device (ATF 34143) is used. Good agreement was obtained between predicted analyses and the simulation results (from Microwave Office (AWR) and Agilent ADS software). For the practical realization, class E PAs were fabricated and tested using PCB FR4. The practical results validate computer simulations and the PAE of the class E PAs are more than 71% and Gain is over 3.8 dB when input power (Pin) is equal to 14 dBm at 2 GHz

The Complementary Strip-Slot: Analysis and Antenna Applications

Aunque el diseño de la antena en un sistema de comunicaciones pueda parecer un problema clásico, los servicios que han aparecido recientemente requieren nuevas funcionalidades, mayores anchos de banda, mejor eficiencia y directividad, así como bajo coste en la fabricación. Las antenas planares han sido unas de las más usadas y estudiadas en las últimas décadas y unas de las mejores candidatas para los nuevos servicios de telecomunicación. Sus ventajas son claras: poco peso, bajo coste y perfil, compatibilidad con la circuitería integrada, pequeño tamaño y reducido coste de fabricación. Sin embargo, su éxito se ha visto limitado por el escaso ancho de banda que presentan. Debido a la naturaleza resonante de la ranura y el parche alimentados por microstrip, sus anchos de banda en impedancia son insuficientes para la mayoría de los servicios de comunicaciones actuales. La mejora de este parámetro ha sido objeto de numerosas investigaciones; sin embargo, este problema sigue sin estar resuelto definitivamente y constituye una línea importante de investigación en antenas planares. Otra limitación de las antenas microstrip es la baja eficiencia de radiación comparada con otras antenas, que se supera combinando varios elementos para formar arrays. Una posibilidad para excitar el array es la alimentación en serie, que tiene las ventajas de simplicidad, menor espacio sobre el sustrato, pérdidas de atenuación más bajas y menor radiación espúrea, comparada con la alimentación corporativa. En esta tesis doctoral se ha propuesto un nuevo elemento radiante, el denominado strip-slot complementario, cuya principal característica es la eliminación de la naturaleza resonante de la antena de ranura excitada a través de línea microstrip por medio de introducir una strip (tira conductora) superpuesta a la ranura y en la cara de la microstrip. Con esta sencilla modificación, se crea una sección acoplada que puede diseñarse para presentar un comportamiento paso-todo. Las principales ventajas de la estructura son su simplicidad, que posee un único sustrato y que no necesita vías, lo que se traduce en bajo coste. Además, su alimentación en serie la hace muy apropiada para construir arrays de onda progresiva. Se ha analizado el comportamiento electromagnético de esta estructura y se ha obtenido un circuito equivalente basado en red en celosía que no sólo explica sus propiedades, sino que permite, además, establecer una eficaz metodología de diseño. Cabe destacar el trabajo relacionado con las redes en celosía. Se ha extraído una propiedad relevante sobre la independencia de las potencias disipadas en esta topología de circuito, que ha permitido explicar por qué la strip no altera las propiedades radiantes de la ranura. Además, esta red circuital se ha propuesto de una forma más general para el modelado de discontinuidades y componentes de LT simétricos, con la ventaja de garantizar la realizabilidad física de sus componentes, a diferencia de las ampliamente usadas redes en T o en π. Una vez caracterizado el elemento radiante propuesto, se ha ilustrado su potencial con una serie de novedosos diseños de arrays de antenas que se benefician de su elevado ancho de banda para proporcionar nuevas funcionalidades. En primer lugar, se estudia el concepto de array más inmediato, que consiste en cargar la línea microstrip con varios elementos strip-slot idénticos. Con un sencillo prototipo, se demuestra la capacidad de escaneo en frecuencia de atrás hacia delante del array (incluyendo broadside) en dos bandas distintas. Además, se diseña y construye un prototipo más sofisticado, que incluye desfasadores entre los elementos, con el objetivo de controlar el ángulo de apuntamiento de forma electrónica, sobre una banda ancha de frecuencias, sin necesidad de modificar la geometría del elemento radiante gracias a su gran ancho de banda. Esta antena representa una contribución importante a las propuestas del estado del arte. A continuación, se estudia el concepto de un array log-periódico basado en el elemento strip-slot, a través de un diseño y su correspondiente prototipo. Para ello, es necesario adaptar la metodología de diseño, concebida para elementos resonantes, y trasladarla al caso de elementos de banda ancha. La reconsideración de dicha metodología puede ser una aportación significativa, puesto que indica la posibilidad de reducción de tamaño (o anchos de banda mayores) cuando se utilizan elementos no-resonantes. Finalmente, se aborda el diseño de un array que implementa la técnica de rotación secuencial con los elementos strip-slot para proporcionar agilidad en polarización. Además, como aplicación del concepto, se incluye la propuesta de una novedosa antena con capacidad diplexora para la recepción simultánea de dos bandas de navegación por satélite, que no requiere de elementos pasivos o activos adicionales. Puesto que se ha presentado una nueva clase de antenas, basada en la estructura radiante de banda ancha strip-slot, y se han diseñado diferentes topologías con características atractivas que contribuyen al estado del arte y son de aplicación en diversos campos, se puede afirmar que esta tesis ofrece una perspectiva nueva para las antenas planares, basadas en elementos no-resonantes

Wide bandwidth focal plane array receiver for radio astronomy

Reflective antennas equipped with phase array feeds (PAFs) have been proposed as part of the Square Kilometre Array reference design, since they offer a wide Field of View (FoV) and large collecting area. To achieve a contiguous FoV, and to cancel spill-over radiation, the Focal Plane Array (FPA) must sample the focal field of the reflector at least every half-wavelength at the upper operating frequency. Low-noise operation over a wide bandwidth requires appropriate impedance matching to the low-noise amplifiers, and this is a challenging research problem since the input impedance of the FPA elements can vary strongly with frequency.Advanced broadband design techniques for antenna arrays have resulted in antenna shapes getting more complex. Modelling of these antennas can only be carried out using numerical computational electromagnetic methods (CEM), and accurate modelling of complex antennas demand the full-wave analysis with fields and currents that vary in three dimensional space. The Frequency Domain Integral Equation model is adopted in this study and used via the Method of Moments (MoM) technique for simulation and modelling of the FPA. The "MoM Antenna Development Toolbox" (MoMADT), 64 bit version of the modelling software, is specifically developed in this study for designing, building and modelling of complex antenna and electromagnetic structures. MoMADT utilizes surface and volume integral equations and provides functions for generating precise meshes and accurate method of moments solutions. MoMADT enables structures to be assembled in an array formation to consist of conductive or dielectric materials, or a combination of both.Study of the wide bandwidth FPA receiver was achieved through analysis of broadband planar antenna structures. This research investigates a unique design solution for a FPA utilizing the diamond planar strip antenna elements arranged to provide three vectors of polarization (triple-polarized FPA). The most promising FPA identified is the 77 Hexagonal Diamond Tripole (HDT) array. This array yields an operating frequency range of 550 to 2100 MHz, providing bandwidth ratio of 3.8:1. It is shown that adequate impedance match can be achieved across the indicated frequency range with desired directivity and gain. In addition, the 77 HDT array offers optimized efficiency and allows the polarization to be distinguished at any angle about the axis normal to the antenna plane to within a theoretical uncertainty of ± 2.2°. This is also true for any function of the FoV allowed by the surface area of the FPA

Millimeter-Wave Components and Antennas for Spatial and Polarization Diversity using PRGW Technology

The evolution of the wireless communication systems to the future generation is accompanied by a huge improvement in the system performance through providing a high data rate with low latency. These systems require access to millimeter wave (mmWave) bands, which offer several advantages such as physically smaller components and much wider bandwidthcomparedtomicrowavefrequencies. However, mmWavecomponentsstillneed a significant improvement to follow the rapid variations in future technologies. Although mmWave frequencies can carry more data, they are limited in terms of their penetration capabilities and their coverage range. Moreover, these frequencies avoid deploying traditional guiding technologies such as microstrip lines due to high radiation and material losses. Hence, utilizing new guiding structure techniques such as Printed Ridge Gap Waveguide (PRGW) is essential in future mmWave systems implementation. ThemainpurposeofthisthesisistodesignmmWavecomponents,antennasubsystems and utilize both in beam switching systems. The major mmWave components addressed in this thesis are hybrid coupler, crossover, and differential power divider where the host guidingstructureisthePRGW.Inaddition,variousdesignsfordifferentialfeedingPRGW antennas and antenna arrays are presented featuring wide bandwidth and high gain in mmWave band. Moreover, the integration of both the proposed components and the featured antennas is introduced. This can be considered as a significant step toward the requirements fulfillment of today's advanced communication systems enabling both space and polarization diversity. The proposed components are designed to meet the future ever-increasing consumer experience and technical requirements such as low loss, compact size, and low-cost fabrication. This directed the presented research to have a contribution into three major parts. The first part highlights the feeding structures, where mmWave PRGW directional couplers and differential feeding power divider are designed and validated. These components are among the most important passive elements of microwave circuits used in antennabeam-switchingnetworks. Different3-dBquadraturehybridcouplersandcrossover prototypes are proposed, featured with a compact size and a wide bandwidth beyond 10 % at 30 GHz. In the second part, a beam switching network implemented using hybrid couplers is presented. The proposed beam switching network is a 4 × 4 PRGW Butler matrix that used to feed a Magneto-electric (ME) dipole antenna array. As a result, a 2-D scanning antenna array with a compact size, wide bandwidth, and high radiation efficiency larger than84%isachieved. Furthergainenhancementof5dBiisachievedthroughdeployinga hybridgainenhancementtechniqueincludingAMCmushroomshapesaroundtheantenna array with a dielectric superstrate located in the broadside direction. The proposed scanning antenna array can be considered as a step toward the desired improvement in the data rate and coverage through enabling the space diversity for the communication link. The final activity is related to the development of high-gain wide-band mmWave antenna arrays for potential use in future mmWave applications. The first proposed configuration is a differential feeding circular polarized aperture antenna array implemented with PRGW technology. Differential feeding antenna designs offer more advantages than single- ended antennas for mmWave communications as they are easy to be integrated with differential mmWave monolithic ICs that have high common-mode rejection ratio providing an immunity of the environmental noise. The proposed differential feeding antenna array is designed and fabricated, which featured with a stable high gain and a high radiation efficiency over a wide bandwidth. Another proposed configuration is a dualpolarized ME-dipole PRGW antenna array for mmWave wireless communication. Dual polarizationisconsideredoneofthemostimportantantennasolutionsthatcansavecosts and space for modern communication systems. In addition, it is an effective strategy for multiple-input and multiple-output systems that can reduce the size of multiple antennas systems by utilizing extra orthogonal polarization. The proposed dual- polarized antenna array is designed to achieve a stable gain of 15 ± 1 dBi with low cross- polarization less than -30 dB over a wide frequency range of 20 % at 30 GHz

Design and analysis of wideband passive microwave devices using planar structures

A selected volume of work consisting of 84 published journal papers is presented to demonstrate the contributions made by the author in the last seven years of his work at the University of Queensland in the area of Microwave Engineering. The over-arching theme in the author’s works included in this volume is the engineering of novel passive microwave devices that are key components in the building of any microwave system. The author’s contribution covers innovative designs, design methods and analyses for the following key devices and associated systems: Wideband antennas and associated systems Band-notched and multiband antennas Directional couplers and associated systems Power dividers and associated systems Microwave filters Phase shifters Much of the motivation for the work arose from the desire to contribute to the engineering o

A compact and portable EMP generator based on Tesla transformer technology

High power electromagnetic pulses are of great importance in a variety of applications such as transient radar, investigations of the effect of strong radio-frequency impulses on electronic systems and modem bio-medical technology. In response to the current trend, a simple, compact, and portable electromagnetic pulse (EMP) radiating source has been developed, based on pulsed transformer technology and capable of producing nanosecond rise-time pulses at voltages exceeding 0.5 MY. For this type of application pulsed transformer technology offers a number of significant advantages over the use of a Marx generator, e.g. design simplicity, compactness and cost effectiveness. The transformer is operated in a dual resonance mode to achieve a high energy transfer efficiency, and although the output voltage inevitably has a slower rise-time than that of a Marx generator, this can be improved by the use of a pulse forming line in conjunction with a fast spark-gap switch. The transformer design is best achieved using a filamentary modeling technique, that takes full account of bulk skin and proximity effects and accurately predicts the self and mutual inductances and winding resistances of the transformer. One main objective of the present research was to achieve a high-average radiated power, for which the radiator has to be operated at a high pulse repetition frequency (pRF), with the key component for achieving this being the spark-gap switch in the primary circuit of the pulsed transformer. Normally a spark-gap switch has a recovery time of about ten milliseconds, and a PRF above 100 Hz is difficult to achieve unless certain special techniques are employed. As the aim of the present study is to develop a compact system, the use of a pump for providing a fluid flow between the electrodes of the spark gap is ruled out, and a novel spark-gap switch was therefore developed based on the principle of corona-stabilization. For simplicity, an omnidirectional dipole-type structure was used as a transmitting antenna. Radiated electric field measurements were performed using a time-derivative sensor, with data being collected by a suitable fast digitizing oscilloscope. Post-numerical processing of the collected data was necessary to remove the ground reflected wave effect. Measurements of the radiated electric field at 10 m from the radiating element indicated a peak amplitude of 12.4 kV/m. Much of the work detailed in the thesis has already been presented in peer reviewed journals and at prestigious international conferences.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Abstracts on Radio Direction Finding (1899 - 1995)

The files on this record represent the various databases that originally composed the CD-ROM issue of "Abstracts on Radio Direction Finding" database, which is now part of the Dudley Knox Library's Abstracts and Selected Full Text Documents on Radio Direction Finding (1899 - 1995) Collection. (See Calhoun record https://calhoun.nps.edu/handle/10945/57364 for further information on this collection and the bibliography). Due to issues of technological obsolescence preventing current and future audiences from accessing the bibliography, DKL exported and converted into the three files on this record the various databases contained in the CD-ROM. The contents of these files are: 1) RDFA_CompleteBibliography_xls.zip [RDFA_CompleteBibliography.xls: Metadata for the complete bibliography, in Excel 97-2003 Workbook format; RDFA_Glossary.xls: Glossary of terms, in Excel 97-2003 Workbookformat; RDFA_Biographies.xls: Biographies of leading figures, in Excel 97-2003 Workbook format]; 2) RDFA_CompleteBibliography_csv.zip [RDFA_CompleteBibliography.TXT: Metadata for the complete bibliography, in CSV format; RDFA_Glossary.TXT: Glossary of terms, in CSV format; RDFA_Biographies.TXT: Biographies of leading figures, in CSV format]; 3) RDFA_CompleteBibliography.pdf: A human readable display of the bibliographic data, as a means of double-checking any possible deviations due to conversion

Multi-Polarized Spiral Antennas for RF Sensing

Spiral antennas are capable of dual polarized operation if the currents can propagate along their arms by going either out or in through the radiation region of the spiral. The wrapping sense of the spiral determines the polarization of the radiated field resulting from this current flow. There are two ways to accomplish this phenomenon over very wide bandwidths. Specifically, either have a feed point for the spiral both outside and inside the radiation region, or use of the modulated arm width (MAW) spiral antenna. The MAW spiral antenna has not been widely accepted and is seldom reported in open literature. Its geometry is however sufficiently unique from the other planar frequency independent (FI) antennas to require a complete explanation of where it fits for different applications, specifically RF sensing. The design of the MAW spiral antenna is detailed herein including geometry described by modulation period, modulation magnitude, expansion rate, total number of arms, feed point structure, termination, cavity, feeding and dielectric effects. The emphasis is on detailed understanding of its performance characteristics such as impedance, pattern control and quality. The relevance of these characteristics to the antenna being used as a sensor is explained. The specific concerns being quantified are location by angle of arrival techniques and polarization detection. The use of a four-arm MAW spiral for angle of arrival as well as polarization sensing is demonstrated theoretically and experimentally. This combined capability has not been mentioned in any literature previously and was investigated thoroughly under this thesis to determine the limitations since as found herein no other four-arm FI planar antenna has this capability. In addition, the application of several geometries of the MAW spiral are examined as possible improvements over the original equiangular geometry including Archimedean, bi-layer, and structures that are not self-complementary due to either the modulation ratio or the period. In particular, pattern performance improvement is demonstrated for modulation periods that do not produce self-complementary geometries while having minimal impact on impedance. Finally, an investigation into the asymmetric modes for an arbitrary number of arms was conducted to evaluate the performance limits of the highest available mode (mode with the largest phase change between arms) of a MAW spiral. Typically, this highest mode has significantly poorer performance than the other modes due to the inability of the MAW spiral to separate it from the modes that are not controlled by the beamformer