Design and Analysis of Substrate-Integrated Cavity-Backed Antenna Arrays for Ku-Band Applications

Mobile communication has become an essential part of our daily life. We love the flexibility of wireless cell phones and even accept their lower quality of service when compared to wired links. Similarly, we are looking forward to the day that we can continue watching our favorite TV programs while travelling anywhere and everywhere. Mobility, flexibility, and portability are the themes of the next generation communication. Motivated and fascinated by such technology breakthroughs, this effort is geared towards enhancing the quality of wireless services and bringing mobile satellite reception one step closer to the market. Meanwhile, phased array antennas are vital components for RADAR applications where the antenna is required to have certain scan capabilities. One of the main concerns in that perspective is how to avoid the potential of scan blindness in the required scan range. Targeting to achieve wide-band wide-scan angle phased arrays free from any scan blindness our efforts is also geared. Conventionally, the key to lower the profile of the antenna is to use planar structures. In that perspective microstrip patch antennas have drawn the attention of antenna engineers since the 1970s due to their attractive features of being low profile, compact size, light weight, and amenable to low-cost PCB fabrication processes. However, patch elements are basically resonating at a single frequency, typically have \u3c2% bandwidth, which is a major deficit that impedes their usage in relatively wide-band applications. There are various approaches to enhance the patch antennas bandwidth including suspended substrates, multi-stack patches, and metalized cavities backing these patches. Metalized cavity-backed patch structures have been demonstrated to give the best performance, however, they are very expensive to manufacture. In this dissertation, we develop an alternative low-cost bandwidth enhancement topology. The proposed topology is based on substrate-integrated waveguides. The great potential of the proposed structure lies in being amenable to the conventional PCB fabrication. Moreover, substrate-integrated cavity-backed structures facilitate the design of sophisticated arrays that are very expensive to develop using the conventional metalized cavity-backed topology, which includes the common broadside arrays used in fixed-beam applications and the scanned phased arrays used in RADAR applications

Dielectric Filled Printed Gap Waveguide for Millimeter Wave Applications

As the communication system goes up to millimeter-wave frequencies for high data rate demands, the conventional microstrip line no longer meets the requirements due to its excessive radiation and harmful surface waves, causing unacceptable insertion loss and interference issues. The radiation and surface waves are absent in the stripline. However, its conductor loss becomes worse due to the narrower strip causing by the implemented two ground planes. In addition, any vertical asymmetry in the stripline can generate unwanted higher order waveguide modes that will be able to propagate wherever the ground planes exist. The standard waveguide technology is not suitable for millimeter-wave bands because of the small dimension of the hole, which causes fabrication challenging and high cost. The new technology of gap waveguide (GW) offers a solution to the above problems in current guiding structures. Considerable effort is being made to miniaturize it using the printed circuit technology for low-cost and low-profile applications. The microstrip-ridge GW and the inverted microstrip GW are the two candidates reported previously. However, they come with their own drawbacks. The tiny air gap makes it very sensitive to the outside pressure or the environmental factors. The plated vias in the copper strip and the electroless nickel immersion gold (ENIG) coating on the strip cause substantial attenuation and a frequency shift. In addition, it is challenging to connect to other transmission lines or conventional rectangular waveguides for the integration and measurements. Therefore, one major part of this thesis is to develop innovative GW structures without the formerly mentioned issues to be suitable for millimeter-wave frequencies and easier implementation. Another major part is developing passive components, such as antenna arrays, using the proposed new GW structures. The third part is studying the GW-based PMC packaging for the irregular ground/PEC plane. This will help extend this new packaging technology from the microstrip line circuits to the substrate integrated waveguide (SIW)- or grounded coplanar waveguide (GCPW)-based circuits

Miniaturization Techniques of Substrate Integrated Waveguide Based on Multilayered Printed Circuit Board Platform

RESUMÉ Le guide d'ondes intégrées au substrat (GIS) est une structure à ondes guidées qui présente des avantages avec un facteur de qualité Q élevé et une excellente isolation ligne à ligne. La technique GIS a été largement utilisé dans la construction de composants passifs, tels que coupleurs, diviseurs, filtres, et déphaseurs. Certains dispositifs actifs ont également été développés avec facteur Q élevé et résonateurs en technologie GIS. En comparant à d'autres types de lignes de transmission planaire, le facteur de qualité Q important du GIS est une embouchure pour son intégration avec d'autres circuits classiques. Les techniques de miniaturisation du SIW sont donc devenues une urgence. Le travail dans cette thèse commence par l'examen et la discussion des techniques de miniaturisation existantes pour GIS, y compris les (ridge substrate integrated waveguide, RSIW), intégrés sur substrat à demi-mode (HMSIW) et les (folded substrata integrated waveguide, FSIW). L'impédance et la constante de propagation des lignes basées sur ces techniques de miniaturisation sont calculées en utilisant la méthode de résonance transversale (transverse resonant method, CRT). Bien que ces paramètres puissent être obtenus par des méthodes de simulation EM, un calcul rapide sera utile pour l’optimisation de la conception en utilisant l'analyse paramétrique. Une préoccupation particulière est axée sur la relation entre la constant d’atténuation et les paramètres géométriques. Les dimensions optimisées de chaque GIS miniaturisés sont proposés en se basant sur l'analyse paramétrique. Les paramètres de transmission de ces lignes de SIW miniaturisés peuvent être extraire en utilisant la méthode à double ligne. Sauf HMSIW, toutes les autres techniques de miniaturisation mentionnées ci-dessus pour la mise en œuvre de la plateforme multicouche. Parmi les techniques de fabrication diverses qui sont en mesure de fournir des substrats multicouches, le circuit imprimé multicouche est utilisé dans la conception des circuits rapportés dans cette thèse.---------- ABSTRACT Substrate integrated waveguide (SIW) is a guided-wave structure that enjoys the benefits of a high Q-factor and an excellent line-to-line isolation. SIW technique has been widely used in building passive components, such as couplers, dividers, filters, and phase shifters. Some active devices have also been developed with high Q-factor SIW resonators. Comparing to other types of planar transmission lines, the big form factor of SIW is a bottleneck for its integration with other conventional integrated circuits. Miniaturization techniques for SIW therefore become very urgent. The work in this dissertation starts with the review and discussion of existing miniaturization techniques for SIW, including ridge substrate integrated waveguide (RSIW), half-mode substrate integrated waveguide (HMSIW) and folded substrata integrated waveguide (FSIW). The impedance and propagation constant of the transmission lines based on these miniaturization techniques are calculated using transverse resonant method (TRM). Although these parameters can be extracted from full wave EM simulations, a fast computation be helpful in design optimization by using parametric analysis. One particular concern focuses on the relationship between attenuation constant and geometric parameters. Optimized dimensions of each miniaturized SIW are suggested based on the parametric analysis. The transmission line parameters of these miniaturized SIW transmission lines can be extracted using dual-line method. Except HMSIW, all other miniaturized techniques mentioned above need multilayer platform for implementation. Among various fabrication techniques which are able to provide multilayered substrate, multilayer printed circuit board is used in the design of the circuits reported in this dissertation. It is believed that the advantages of SIW circuit are important in millimeter wave applications, although the design might limit the operating frequency. Specifically, Rogers substrate R6002 is used in all our designs for proving the concepts investigated in this work. One principal step for using the SIW technology is to develop high-performance transitions and interconnects between substrate integrated circuits (SICs) and other types of transmission lines or circuits embedded in or surface mounted on the multilayer substrates. In this work, a novel transition between a microstrip line and an SIW in a multilayer substrate design environment is presented

Design of new radiating systems and phase shifters for 5G communications at millimeter-wave frequencies

With the arrival of the new generation of communications, known as 5G, the systems that constitute it must offer better performance in terms of data speed, latency and connection density than the previous generation of communications. For 5G, an allocation of the frequency ranges that will support future wireless communications has been established. This allocation is formed by a range of frequencies corresponding to bands below 6 GHz and the other range of frequencies includes bands above 24 GHz. In the latter frequency range, which includes part of the millimeter-wave frequency band (from 30 GHz to 300 GHz), the development of new radio frequency (RF) components is necessary because their design and manufacture is a technological challenge. As the frequency that supports wireless communications increases, propagation losses also increase. Therefore, these losses must be compensated by the radiating systems in 5G to make these communications possible. The RF devices that make up these new systems must provide high antenna gain, be power efficient and offer spatial reconfigurability of the radiated signal. In this thesis, the main objective is the design of both guided and radiating RF devices to provide design solutions for future 5G systems at millimeter-wave frequencies. In particular, the contributions made have been to the design of phase shifters and antenna arrays. To improve efficiency at millimeter-wave frequencies, these devices have been designed in waveguide technology. Phase shifters are essential RF devices to control the phase shift of the electromagnetic wave that will be radiated to a certain spatial direction by an antenna array. The design of beamforming networks requires the implementation of phase shifters that produce a fixed or variable phase shift value. However, the design and fabrication of these devices at millimeter-wave frequencies is a complex task. In this thesis, four designs of waveguide phase shifters that produce both fixed and variable phase shift are presented. For phase shifters that provide a fixed phase shift, the value of this phase shift along the frequency is tuned in a desired manner by using periodic structures with higher symmetries. These types of configurations provide both flexibility in the design process and improved electromagnetic performance such as greater operating bandwidth. All the phase shifters have been implemented in gap-waveguide technology to demonstrate its effectiveness in these devices for millimeter-wave frequencies. Regarding the radiating systems, two feeding strategies have been considered in the design process. First, the design of a 70 GHz centered antenna array implemented in gap-waveguide technology combined with the use of separate waveguides in E-plane is proposed. In this design, the feed is guided through a waveguide corporate-feed network. Second, the design of a reflectarray whose unit cells are formed using three-dimensional geometries is presented. In this case, the feeding is done in free space by radiation from a source antenna. In the previous designs, the fabrication of the prototypes was done by 3D printing based on stereolithography. Finally, using unit cells with three-dimensional geometries, the design of radiating devices with more complex functionalities such as reflection/transmission with high directivity and reconfiguration of the reflected radiation by means of graphene structures are proposed.Con la llegada de la nueva generación de comunicaciones, denominada 5G, los sistemas que la conforman deben ofrecer unas mejores prestaciones en términos de velocidad de datos, latencia y densidad de conexiones respecto a la generación de comunicaciones anterior. Para 5G se ha establecido una asignación de los rangos de frecuencia que van a soportar las futuras comunicaciones inalámbricas. Esta asignación se compone por un rango de frecuencias correspondiente a las bandas por debajo de los 6 GHz y el otro rango de frecuencias engloba a las bandas por encima de los 24 GHz. En este ´ultimo rango de frecuencias, en el cual están incluidas parte de la banda de las frecuencias milimétricas (desde 30 GHz a 300 GHz), es necesario el desarrollo de nuevos componentes de radiofrecuencia (RF) ya que su diseño y fabricación supone un reto tecnológico. Al aumentar la frecuencia que soporta las comunicaciones inalámbricas, las pérdidas por propagación también aumentan. Es por ello por lo que estas pérdidas deben ser compensadas por los sistemas radiantes en 5G para que las comunicaciones sean posibles. Los dispositivos de RF que componen estos nuevos sistemas deben proporcionar una alta ganancia de antena, ser eficientes en términos de potencia y ofrecer reconfigurabilidad espacial de la señal radiada. En esta tesis, el objetivo principal es el diseño de dispositivos de RF tanto guiados como radiantes para ofrecer soluciones de diseño a los futuros sistemas 5G en frecuencias milimétricas. De manera particular, las contribuciones realizadas han sido al diseño de desfasadores y agrupaciones de antenas. Para mejorar la eficiencia en frecuencias milimétricas, estos dispositivos han sido diseñados en tecnología en guía de ondas. Los desfasadores son dispositivos RF esenciales para controlar el desfase de la onda electromagnética que será radiada hacia una cierta dirección espacial por una agrupación de antenas. Las redes de beamforming tienen la necesidad de implementar en su diseño desfasadores que producen un valor de desfase fijo o variable. Sin embargo, el diseño y fabricación de estos dispositivos en frecuencias milimétricas resulta una tarea de alta dificultad. En esta tesis se presenta cuatro diseños de desfasadores en guía de onda que producen un desfase tanto fijo como variable. Para los desfasadores que proporcionan un desfase fijo, el valor de este desfase a lo largo de la frecuencia es ajustado de manera deseada mediante el uso de estructuras periódicas con simetrías superiores. Este tipo de configuraciones proporcionan tanto flexibilidad en el proceso de diseño como una mejora de las características electromagnéticas como puede ser un mayor ancho de banda de operación. Todos los desfasadores realizados han sido implementados en tecnología gap waveguide para demostrar su efectividad en estos dispositivos para frecuencias milimétricas. Respecto a los sistemas radiantes, se han considerado dos estrategias de alimentación en el proceso diseño. En primer lugar, se propone el diseño de un array centrado a 70 GHz implementado en tecnología gap waveguide combinado con el uso de guías de onda separadas en plano E. En este diseño, la alimentación es guiada a través de una red de alimentación corporativa en guía de onda. En segundo lugar, se presenta el diseño de un reflectarray cuyas celdas unitarias son formadas mediante geometrías tridimensionales. En este caso, la alimentación se hace en el espacio libre mediante la radiación de una antena fuente. En los anteriores diseños, la fabricación de los prototipos se realizó mediante impresión 3D basado en estereolitografía. Finalmente, a través del uso de celdas unitarias con geometrías tridimensionales, se proponen el diseño de dispositivos radiantes con funcionalidades más complejas como la reflexión/transmisión con alta directividad y la reconfiguración de la radiación reflejada mediante estructuras con grafeno.Tesis Univ. Granada

Analysis and design of new electronically reconfigurable periodic leaky-wave antennas

[SPA] El principal objetivo de la tesis es el estudio de nuevas tecnologías en el campo de las antenas reconfigurables. En particular, la tesis se centra en explorar y explotar el potencial que presentan un tipo de antenas denominadas como ¿Antenas basadas en Modos de Fuga¿ para controlar electrónicamente su diagrama de radiación. La tesis desarrolla el análisis, diseño y fabricación de tres novedosas antenas basadas en modos de fuga capaces de variar mediante unas pocas señales de control y de forma continua su ángulo de apuntamiento. El mecanismo de reconfiguración electrónica principalmente se basa en el control de la dispersión de los modos de fuga excitados en dichas estructuras, mediante un control electrónico introducido empleando estructuras periódicas resonantes combinadas con elementos activos tales como diodos varactores. La tesis demuestra claramente la utilidad de estas antenas en el campo de la reconfiguración electrónica, proponiendo estas nuevas estructuras como alternativas a otras soluciones más clásicas (como antenas en array de fase reconfigurables o reflectores parabólicos mecánicamente re-orientables mecánicamente) y otras de actualidad (como reflectarrays, transmitarrays, antenas metamateriales o antenas pixeladas), las cuales todas ellas presentan otros problemas en términos de coste, complejidad de diseño o limitaciones de escalabilidad en frecuencia, aportando así esta tesis novedosos conceptos de reconfiguración electrónica.[ENG] The thesis aims the design of novel reconfigurable antennas with electronic beam-scanning. In particular, the antennas analyzed are known as Fabry-Perot Antennas (FPA) and are currently of high interest in the scientific community because of their high-directivity, low-profile and structure simplicity, what allow them to be an interesting alternative to other technologies (e.g. parabolic reflectors, phased arrays, etc.) which require of complex power distribution networks, bulky external sources or costly techniques to achieve reconfigurable capabilities. In this thesis, the integration of active components, such as varactor diodes, with FPRA structures, is exploited to achieve electronic control of their aperture illumination, which in turn results in the electronic steering of the radiation-pattern main beam. A modal analysis based on the leaky-wave theory has allowed to understand and predict the behavior of these structures. An equivalent circuit model was developed to design and optimize the dimensions of theses complex structures, saving computational cost and time. The antennas are based on the control of the frequency dispersion response and the electromagnetic band-gap (EBG) properties of periodic structures, employing specially designed Frequency-Selective Surfaces (FSS) loaded with varactor diodes. Three novel antenna prototypes were manufactured to demonstrate electronic steering capability operating at 5.5GHz. Continuous scanning in elevation (1D scanning) and also in elevation and azimuth simultaneously (2D scanning) have been achieved employing just a few control signals (between 1 and 4 signals). The antenna structures have been implemented in a low-cost technology based on parallel plate waveguides and printed circuit boards which have allowed to design antennas with a reduced profile. Theoretical, simulated and experimental results are shown for each prototype to demonstrate the concepts. Also, some future lines related to novel planar reconfigurable antennas in development are also outlined. One of the main potential advantages of the reconfiguring principles presented for future applications is their frequency scalability. This would allow to apply these concepts to other technologies, such as MEMS or graphene, to build new reconfigurable antennas able to operate at higher frequency bands (e.g. mm-bands) for future applications.Universidad Politécnica de Cartagen

Efficient solid state power amplifiers: power combining and highly accurate AM/AM and AM/PM behavioural models with application to linearisation

Radio Frequency (RF) Power Amplifiers (PAs) are a major contributor to modern communication systems, both in terms of being an enabling technology as well as having the most impact on overall system availability, linearity and power consumption. In order to achieve the most optimum system outcome there needs to be an appropriate method for selecting the most suitable RF PA design approach, as well as being able to select the most appropriate RF PA output device, based on a range of varying requirements, specifications and technologies. The ability to perform these tasks quickly, with improved accuracy, using existing available device data, with minimal or no further device testing and from a range of existing and emerging technologies would provide RF PA designers with significant benefits. The investigations and research provided in this thesis consider a range of existing and emerging RF PA technologies and power combining methods and compares them via a new selection and design methodology developed in this thesis. The new methodology builds on modern design and statistical approaches including manufacturing options that enable an appropriate technology to be selected for Solid State Power Amplifier (SSPA) design. In addition to hard design specifications, the current thesis also considers less tangible specifications, such as graceful degradation, time tomarket and ease of use, as well as alternative design approaches, such as fuzzy logic approaches. With a suitable technology approach determined, a selection of a suitable RF output device(s) is considered. As the demand for new communication services continues to increase, requiring tighter specifications and reduced product delivery time scales, then the ability to accurately and quickly compare available RF PA devices from a range of device technologies or devices from different manufacturers, at both the system and component level, makes such a selection paramount. In this thesis, simplememoryless (AmplitudeModulation/AmplitudeModulation (AM/AM) only) and Quasi-Memoryless (QM) Behavioural Models (BMs) (AM/AM combined with Amplitude Modulation/Phase Modulation (AM/PM)) are reviewed, extended and improved upon, with up to 20 dB Normalised Mean Squared Error (NMSE) modelling improvement achieved over a range of technologies, allowing effective RF PA device selection using these newly developed simple and fast models. This thesis uses recent existing accurate and powerful semi-physical memoryless BMs, suited to RF PA devices, and develops and extends their use for QM modelling. The trade-off from the improvement in the overall accuracy is some further simple processing steps. Furthermore, this thesis also provides a comparison of other models, presented in the literature. The improved simple RF PA device models and extension techniques presented in this thesis show, via simulation and measurement, that the new models are suitable for use over a wide range. Lineariser improvements, linked to the accuracy improvements of the proposed models of this thesis, are also investigated, showing further benefits from this research. Physically based simple QM BMs are also used to model thermal and bias network memory effects, which are becomingmore relevant tomodern communication services that use wider bandwidths, enabling the impacts of RF PA device memory effects to be determined and compared. The feasibility of the developed models and improvements are also utilised in the simulation of a low cost RF PA lineariser. With the trend to smaller localised low cost and power RF mobile wireless repeater cells being away from larger more expensive and complex hardware, used to perform linearisation, this thesis presents a trade-off between complexity and linearisation performance and demonstrates, through modelling and simulation, that 8-10 dB improvement in linearisation performance is achievable with the use of the newly developed models.Thesis (Ph.D.) -- University of Adelaide, School of Electrical and Electronic Engineering, 201

Analysis and design of hybrid leaky-wave antennas loaded with frequency selective surfaces

[SPA] En esta tesis se propone una nueva antena de tipo Leaky-Wave (Leaky Wave Antenna, LWA). Estas antenas han recibido mucha atención en las últimas décadas por ser altamente directivas. En concreto, constituyen una solución especialmente atractiva para aplicaciones que requieran altas prestaciones y precisión, como en sistemas de comunicación por satélite y radar. Concretamente, las LWAs consideradas en esta tesis se basan en la radiación producida por una onda de fuga que se propaga por una cavidad resonante. Estas LWAs se denominan de tipo Fabry-Perot, por su analogía con los interferómetros. En concreto, se propone una nueva antena donde la cavidad Fabry-Perot se crea entre dos superficies selectivas en frecuencia (Frequency Selective Surface, FSS), una situada en la parte superior y que actúa como superficie parcialmente reflectante (Partially Reflective Surface, PRS) y otra situada en la parte inferior actuando como superficie de alta impedancia (High Impedance Surface, HIS). Debido a esta composición, denominamos la antena como PRS-HIS-LWA. Las dos FSS consisten en un sustrato dieléctrico impreso con parches metálicos. La principal ventaja de la nueva antena es que permite controlar las características de su diagrama de radiación de una forma flexible y precisa no conocida hasta la fecha. En el primer capítulo se describe la motivación de esta tesis, los objetivos planteados y se clarifican sus principales contribuciones originales. El segundo capítulo se centra en la caracterización eficiente de las superficies periódicas (FSS) que formarán parte de la PRS-HIS-LWA. Se trata de un paso clave, que permitirá el análisis y diseño de forma eficiente de la antena en su totalidad. Se proponen diversos métodos originales para la caracterización de FSSs, y se demuestra su alta eficiencia y utilidad no sólo en el marco de esta tesis, sino en el estudio de muchos otros dispositivos. En el tercer y cuarto capítulos se realiza el análisis y diseño de PRS-HIS-LWAs, comenzando por el caso de una estructura unidimensional (1D) y pasando después al bidimensional (2D). Ambas estructuras son interesantes desde el punto de vista práctico. Las antenas 1D son útiles para aplicaciones donde sea necesario escanear el punto del espacio hacia el que se dirige la radiación (escaneo del haz). Por otro lado, las 2D poseen la capacidad de apuntar hacia el cenit (broadside) con un lóbulo de radiación tipo lápiz muy directivo. El tercer capítulo de la tesis se centra en el análisis y diseño de PRS-HIS-LWAs 1D y 2D uniformes, es decir, en ellas la geometría de la PRS y la HIS permanece constante a lo largo de toda la antena. Se lleva a cabo el análisis de la PRS-HIS-LWA mediante el uso de una red equivalente transversa (Transverse Equivalent Network, TEN) en la que se incluyen las expresiones presentadas en el capítulo 2. Este análisis posibilita el estudio de la influencia de la geometría de la PRS y la HIS en el comportamiento de la antena. En concreto, se concluye que la PRS controla principalmente la tasa de radiación de la antena (y por lo tanto su ancho de haz) y que la HIS proporciona el control sobre ángulo de apuntamiento. En el capítulo cuarto se realiza la síntesis del diagrama de radiación de la PRS-HIS-LWAs tanto en el caso 1D como 2D. A partir de unos requerimientos del diagrama de radiación (ángulo de apuntamiento, ancho de haz, nivel de lóbulo principal a secundario, eficiencia de radiación, eficiencia de iluminación) se obtiene la tasa de radiación y ángulo de apuntamiento que debe presentar la antena en cada punto de su apertura radiante. Para obtener estas características es necesario utilizar los resultados obtenidos en el capítulo anterior y modular la geometría de la PRS y la HIS a lo largo de la estructura. De este modo se diseñan antenas no uniformes, o también llamadas “taper” donde la geometría de las superficies periódicas se ha modulado para sintetizar un determinado diagrama de radiación. Se propone una técnica sistemática totalmente novedosa para realizar esta síntesis, y se aplica en concreto en el caso de reducción de nivel de lóbulo principal a secundario en una antena 1D y en el caso de optimizar las eficiencias de radiación e iluminación en antenas 2D. En el quinto y último capítulo de esta tesis se presentan las conclusiones obtenidas del trabajo realizado así como las líneas futuras de investigación que sugiere. [ENG] This thesis proposes a new type antenna Leaky-Wave (Leaky Wave Antenna, LWA). These antennas have received much attention in the past decades to be highly directives. In particular, constitute an especially attractive solution for applications requiring high performance and precision, as in satellite communication systems and radar. Specifically, the Lwas considered in this thesis are based on the radiation produced by a leakage wave that propagates through a resonant cavity. These are referred Lwas Fabry-Perot type, by analogy with the interferometers. Specifically, it proposes a new antenna where Fabry-Perot cavity is created between two frequency selective surfaces (Frequency Selective Surface, HSS), one located at the top surface and serving as partially reflective (partially reflective surface, PRS) and one located on the bottom surface acting as a high impedance (High Impedance Surface, HIS). Because of this composition, called the antenna as PRS-HIS-LWA. The two FSS consist of a dielectric substrate with printed metallic patches. The main advantage of the new antenna is that it allows the characteristics of the radiation pattern of a flexible and precise unknown to date. The first chapter describes the motivation of this thesis, the objectives and clarified its main original contributions. The second chapter focuses on the efficient characterization of regular surfaces (FSS) that form part of the PRS-HIS-LWA. This is a key step that will allow the analysis and design of the antenna efficiently as a whole. Several methods are proposed to characterize original FSSS, and demonstrated its high efficiency and usefulness not only in the context of this thesis, but in the study of many other devices. In the third and fourth chapters of the study design and analysis of PRS-HIS-lwas, starting with the case of a one-dimensional structure (1D) and then moving to two-dimensional (2D). Both structures are interesting from a practical standpoint. 1D antennas are useful for applications where it is necessary to scan the space to the point that directs radiation (beam scanning). On the other hand, possess the ability 2D point toward the zenith (broadside) with a radiation lobe of highly directive pencil type. The third chapter of the thesis focuses on the analysis and design of PRS-HIS-1D and 2D Lwas uniform, ie, including the geometry of the PRS and HIS remains constant throughout the antenna. It carries out the analysis of the PRS-HIS-LWA using a network equivalent transverse (transverse Equivalent Network, TEN) which includes expressions presented in chapter 2. This analysis allows the study of the influence of the geometry of the PRS and the HIS antenna behavior. Specifically, it is concluded that the PRS mainly controls the rate of radiation of the antenna (and therefore its beamwidth) and which provides control over HIS pointing angle. The fourth chapter synthesis is performed radiation diagram of the PRS-HIS-Lwas both 1D and 2D case. From a radiation pattern requirements (pointing angle, beam width, main lobe level of secondary radiation efficiency, illumination efficiency) is obtained radiation rate and pointing angle of the antenna to be present in each radiant opening point. To obtain these characteristics it is necessary to use the results obtained in the previous chapter modular geometry HIS PRS and along the structure. Thus antennas are designed uniform, or so-called "taper" where the periodic surface geometry has been modulated to synthesize a particular radiation pattern. It proposes a completely novel technique for performing systematic this synthesis, and in particular applies in the case of reduction of main lobe level at an antenna side and in the case 1D optimize efficiencies in radiation and illumination 2D antennas. In the fifth and final chapter of this thesis presents the conclusions of the work and future lines of research that suggests.Universidad Politécnica de Cartagen

Design and Implementation of High Gain 60 GHz Antennas for Imaging/Detection Systems

Recently, millimeter wave (MMW) imaging detection systems are drawing attention for their relative safety and detection of concealed objects. Such systems use safe non-ionizing radiation and have great potential to be used in several applications such as security scanning and medical screening. Antenna probes, which enhance system performance and increase image resolution contrast, are primarily used in MMW imaging sensors. The unlicensed 60 GHz band is a promising band, due to its wide bandwidth, about 7 GHz (57 - 64 GHz), and lack of cost. However, at 60 GHz the propagation loss is relatively high, creating design challenges for operating this band in MMW screening. A high gain, low profile, affordable, and efficient probe is essential for such applications at 60 GHz. This thesis’s focus is on design and implementation of high gain MMW probes to optimize the performance of detection/imaging systems. First, single-element broadside radiation microstrip antennas and novel probes of endfire tapered slot high efficient antennas are presented. Second, a 57-64 GHz, 1 × 16-element beam steering antenna array with a low-cost piezoelectric transducer controlled phase shifter is presented. Then, a mechanical scanner is designed specifically to test proposed antenna probes utilizing low-power 60 GHz active monostatic transceivers. The results for utilizing proposed 60 GHz probes show success in detecting and identifying concealed weapons and explosives in liquids or plastics. As part of the first research theme, a 60 GHz circular patch-fed high gain dielectric lens antenna is presented, where the prototype’s measured impedance bandwidth reaches 3 GHz and a gain of 20 dB. A low cost, 60 GHz printed Yagi antenna array was designed, optimized, fabricated and tested. New models of the antipodal Fermi tapered slot antenna (AFTSA) with a novel sine corrugated (SC) shape are designed, and their measured results are validated with simulated ones. The AFTSA-SC produces a broadband and high efficiency pattern with the capacity for high directivity for all ISM-band. Another new contribution is a novel dual-polarized design for AFTSA-CS, using a single feed with a pair of linearly polarized antennas aligned orthogonally in a cross-shape. Furthermore, a novel 60 GHz single feed circularly polarized (CP) AFTSA-SC is modeled to radiate in the right-hand circularly polarized antenna (RHCP). A RHCP axial ratio bandwidth of < 3dB is maintained from 59 to 63 GHz. In addition, a high gain, low cost 60 GHz Multi Sin-Corrugations AFTSA loaded with a grooved spherical lens and in the form of three elements to operate as the beam steering antenna is presented. These probes show a return loss reduction and sidelobes and backlobe suppression and are optimized for a 20 dB or higher gain and radiation efficiency of ~90% at 60 GHz. The second research theme is implementing a 1 × 16-element beam steering antenna array with a low-cost piezoelectric transducer (PET) controlled phase shifter. A power divider with a triangular feed which reduces discontinuity from feed lines corners is introduced. A 1 × 16-element array is fabricated using 60 GHz AFTSA-SC antenna elements and showed symmetric E-plane and H-plane radiation patterns. The feed network design is surrounded by electromagnetic band-gap (EBG) structures to reduce surface waves and coupling between feed lines. The design of a circularly polarized 1 × 16-element beam steering phased array with and without EBG structures also investigated. A target detection investigation was carried out utilizing the proposed 60GHz antennas and their detection results are compared to those of V-band standard gain horn (SGH). System setup and signal pre-processing principle are introduced. The multi-corrugated MCAFTSA-SC probe is evaluated with the imaging/detection system for weapons and liquids concealed by clothing, plywood, and plastics. Results show that these items are detectable in clear 2D image resolution. It is believed that the 60 GHz imaging/detection system results using the developed probes show potential of detecting threatening objects through screening of materials and public

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