Reconfigurable Antennas

In this new book, we present a collection of the advanced developments in reconfigurable antennas and metasurfaces. It begins with a review of reconfigurability technologies, and proceeds to the presentation of a series of reconfigurable antennas, UWB MIMO antennas and reconfigurable arrays. Then, reconfigurable metasurfaces are introduced and the latest advances are presented and discussed

Review on Design of Frequency Selective Surfaces based on Substrate Integrated Waveguide Technology

The spectacular development of frequency selective surfaces (FSS) as a spatial filter, absorbers and reflectors made them feasible for the aerospace and defence applications. The intervention of substrate integrated waveguide (SIW) technology into FSS results in the improvement of unit cell structures and better performance by isolating them from inter-element interference. Such FSS structures with SIW cavities upholds the FSS properties and improves their selectivity and performance. Considering the diversity in applications of introducing SIW cavity technology into FSS, the aim of this paper is to furnish a study on the glimpse of EM design techniques to analyze this type of structures. Design topologies of narrowing bandwidth, dual resonance, the design of FSS with sharp sideband edges and frequency selective polarization rotating structures are presented. Further, a novel design for improving the bandwidth of reflective FSS is discussed based on SIW technology. Fabrication techniques pertaining to this type of structures are presented in brief

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

Mutual Coupling Considerations in the Development of Multi-feed Antenna Systems

In the design of any multi-port network with more than one antenna, mutual coupling between these different ports must be accounted for. In an effort to investigate and control these mutual coupling effects, we have selected three structures to be thoroughly analyzed. Furthermore, they have been fabricated and tested to develop relevant design guides for these selected structures to have minimal mutual coupling effects. These selected structures included a feed network for a multi-port antenna, a dual feedhorn for a large reflector antenna, as well as a set of Multi- Input Multi-Output (MIMO) laptop antennas. In the first study, we analyzed a 30- port radial splitter that can be used for an in-phase feeding of a 30-high power transmitter. Our objectives here have been geared towards estimating the mutual coupling between the 30 ports and exploring the port and alignment failure analysis, its graceful degradation results, and relevant efficiency performance for such high power multi-port network will be presented. In the second study, we investigated the mutual coupling of a multifeedhorn structure of a large reflector antenna in order to allow multi-beam radiation or reception. This high gain antenna utilizes integrated feeds with precise physical tight spacing and could suffer from strong inter-coupling. Mutual coupling effects here include input match deterioration, beam width broadening, and cross-polarization degradation due to the proximity coupling of these various feeds. Our study derived accurate feed location expressions as well as methods to improve the decoupling between the feeds that have been implemented. These results will be discussed. For the third study, we carried out extensive investigates into the mutual coupling effects amidst wireless laptop antennas for a MIMO system implementation. For a laptop use, it is required to determine the best location, optimum spacing, and orientations of these antennas in order to achieve the maximum benefits of the system’s diversity. First, we studied the coupling between two antennas as a function of their spacing, types, and orientations. Subsequently, we extended the study to a controlled multi-antenna system for a MIMO implementation. Design rules for such implementation have been derived and will be discussed in detail

Antenna Designs for 5G/IoT and Space Applications

This book is intended to shed some light on recent advances in antenna design for these new emerging applications and identify further research areas in this exciting field of communications technologies. Considering the specificity of the operational environment, e.g., huge distance, moving support (satellite), huge temperature drift, small dimension with respect to the distance, etc, antennas, are the fundamental device allowing to maintain a constant interoperability between ground station and satellite, or different satellites. High gain, stable (in temperature, and time) performances, long lifecycle are some of the requirements that necessitates special attention with respect to standard designs. The chapters of this book discuss various aspects of the above-mentioned list presenting the view of the authors. Some of the contributors are working strictly in the field (space), so they have a very targeted view on the subjects, while others with a more academic background, proposes futuristic solutions. We hope that interested reader, will find a fertile source of information, that combined with their interest/background will allow efficiently exploiting the combination of these two perspectives

Gradient metasurfaces: a review of fundamentals and applications

In the wake of intense research on metamaterials the two-dimensional analogue, known as metasurfaces, has attracted progressively increasing attention in recent years due to the ease of fabrication and smaller insertion losses, while enabling an unprecedented control over spatial distributions of transmitted and reflected optical fields. Metasurfaces represent optically thin planar arrays of resonant subwavelength elements that can be arranged in a strictly or quasi periodic fashion, or even in an aperiodic manner, depending on targeted optical wavefronts to be molded with their help. This paper reviews a broad subclass of metasurfaces, viz. gradient metasurfaces, which are devised to exhibit spatially varying optical responses resulting in spatially varying amplitudes, phases and polarizations of scattered fields. Starting with introducing the concept of gradient metasurfaces, we present classification of different metasurfaces from the viewpoint of their responses, differentiating electrical-dipole, geometric, reflective and Huygens' metasurfaces. The fundamental building blocks essential for the realization of metasurfaces are then discussed in order to elucidate the underlying physics of various physical realizations of both plasmonic and purely dielectric metasurfaces. We then overview the main applications of gradient metasurfaces, including waveplates, flat lenses, spiral phase plates, broadband absorbers, color printing, holograms, polarimeters and surface wave couplers. The review is terminated with a short section on recently developed nonlinear metasurfaces, followed by the outlook presenting our view on possible future developments and perspectives for future applications.Comment: Accepted for publication in Reports on Progress in Physic

Investigation of Radar Signal Interaction with Crossflow Turbine for Aviation Application

The increased adoption of wind energy is an important part of the push towards a net zero-emission economy. One obstacle that stands in the way of a higher rate of wind energy adoption is the interference that wind turbines cause to nearby radar installations. Wind turbines negatively affect the performance of nearby radar sites in a variety of different ways. Almost all types of radar are affected in at least one of these ways.In order to understand the degree to which an object such as a wind turbine interacts with radar, it is important to have detailed radar cross section (RCS) data for the object. In this work, a novel, low-cost, scale model radar cross section characterization system is presented with various advantages over traditional designs. This system was used to characterize the RCS of the novel Crossflow wind turbine. Additionally, work has been carried out on the characterization of metamaterial absorber coatings that can be applied to new and existing turbines for the purposes of reducing their radar cross section and the degree to which they cause radar inter-ference. The works presented can be leveraged to reduce concerns around radar interference from wind turbines, as well as to iteratively generate ge-ometries with lower radar cross sections for the aviation and infrastructure sectors, ultimately accelerating the pace of wind energy adoption and the move towards a net zero-emission economy

Dual-band beam scanning reflectarrays and novel wideband and polarization diversified planar antennas

The reflectarray antenna has been considered as a suitable candidate to replace the traditional parabolic reflectors because of its high-gain and low-profile features. Beam scanning capability and multi-band operation are the current trends of the reflectarray design. It is desired to implement these functionalities with simple and effective techniques. Narrow bandwidth is the main issue which restricts the applications of the microstrip antennas. New microstrip slot antennas and polarization diversified planar antennas are introduced as the solutions to the issue of narrow bandwidth in this dissertation. A dual-band beam scanning reflectarray has been developed. It is the first offset-fed reflectarray that has been ever practically developed to emulate a cylindrical/parabolic type of reflector. Unlike other beam scanning reflectarrays which integrate phase tuning devices into the reflectarray elements and control the reflection phase, the beam scanning capability of this reflectarray is provided by its feed array. This method significantly reduces the complexity of the design of the beam scanning reflectarray. A new dual-band reflectarray configuration is also developed to eliminate the possible top layer blocking effects in the dual-layer reflectarray configuration. Perforated patches loaded with slots on the ground plane and rectangular patches loaded with slots on the patches are adopted as the low and high frequency bands, respectively. It is guaranteed that no physical contact between any two elements will occur. The bandwidth of the conventional microstrip antenna is small. A new wideband circularly polarized microstrip slot antenna is introduced in this dissertation. Very wide 3-dB axial ratio bandwidth is observed for the proposed antenna. The antennas are assembled in triangularly arranged array with sequential rotation feed technique. Polarization polarity is an alternative solution to the narrow bandwidth. A reconfigurable circularly polarized microstrip antenna is proposed. The antenna has both right-hand and left-hand circular polarizations which are controlled by two piezoelectric transducers. In addition, a dual-band dual-linearly-polarized planar array is designed based on the concepts of polarization diversity and multi-band operation. The research presented in this dissertation suggests useful techniques for reflectarrays and novel antenna designs. The results should have many applications for the modern wireless communication and radar systems