Dissertations / Theses: 'Artificial magnetic conductor'

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Almutawa, Ahmad Tariq. "Log-Periodic Microstrip Patch Antenna Miniaturization Using Artificial Magnetic Conductor Surfaces." Scholar Commons, 2011. http://scholarcommons.usf.edu/etd/2982.

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Microstrip patch antennas are attractive for numerous military and commercial applications due to their advantages in terms of low-profile, broadside radiation, low-cost, low-weight and conformability. However, the inherent narrowband performance of patch antennas prohibits their use in systems that demand wideband radiation. To alleviate the issue, an existing approach is to combine multiple patch antennas within a log-periodic array configuration. These log-periodic patch antennas (LPMAs) are capable of providing large bandwidths (>50%) with stable broadside radiation patterns. However, they suffer from electrically large sizes. Therefore, their miniaturization without degrading the bandwidth performance holds promise for extending their use in applications that demand conformal and wideband installations. In recent years, electromagnetic band gap structures have been proposed to enhance the radiation performances of printed antennas. These engineered surfaces consist of a periodic arrangement of unit cells having specific metallization patterns. At particular frequencies, they provide a zero-degree phase shift for reflected plane waves and effectively act as high impedance surfaces. Since, their band-limited electromagnetic field behavior is quite similar to a hypothetical magnetic conductor; they are also referred to as artificial magnetic conductors (AMCs). AMC structures were shown to allow lower antenna profile, larger bandwidth, higher gain, and good unidirectional radiation by alleviating the field cancellation effects observed in ground plane backed antenna configurations. Previous research studies have already demonstrated that microstrip patch antennas can enjoy significant size reductions when placed above the AMC surfaces. This project, for the first time, investigates the application of AMCs to LPMA configurations. Specifically, the goal is to reduce the LPMA size while retaining its highly desired large bandwidth performance. To accomplish this, we employ various AMC surface configurations (e.g. uniform, log-periodic) under traditional LPMAs and investigate their performance in terms of miniaturization, bandwidth, gain, and radiation patterns.

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Visser, Hugo Hendrik. "An artificial magnetic ground-plane for a log-periodic antenna." Thesis, Stellenbosch : University of Stellenbosch, 2010. http://hdl.handle.net/10019.1/4176.

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Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2010.
ENGLISH ABSTRACT: This paper presents the implementation of an artificial magnetic ground-plane with a low profile Log-periodic Dipole Array (LPDA) antennas. After the properties of three typical Electromagnetic Bandgap (EBG) structures are investigated and their bandwidth properties are studied, a mechanism is presented to improve the band-width over which the EBG surface acts as a perfect magnetic conductor (PMC). A low profile LPDA is modeled above this surface and the results indicate an improved band-width region. Compared with a LPDA in free space the frequency band is shifted higher by the EBG surface and the gain pattern is shifted from a horizontal orientation to a vertical orientation.
AFRIKAANSE OPSOMMING: Hierdie dokument stel voor die implementering van kunsmatige magnetiese grondvlakke met Logaritmiese Periodiese Dipool Samestelling (LPDS) antennas. Die eienskappe van drie tipiese Elektromagnetiese Bandgaping (EBG) strukture word ondersoek en hul bandwydte eienskappe word bestudeer. ’n Meganisme word voorgestel om die bandwydte te verbeter waar die EBG oppervlakte soos n perfekte magnetiese geleier optree. ’n Lae profiel LPDS word bo hierdie oppervlakte geplaas. Die resultate dui aan ’n verbetering in the bandwydte. In vergelyking met ’n LPDS in vrye ruimte skuif die frekwensie band ho¨er as gevolg van die EBG oppervlakte en die aanwins patroon skuif van ’n horisontale orientasie na ’n vertikale orientasie.

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Kostka, Darryl. "Enhancement of printed inductors using artificial magnetic conductor (AMC) surfaces for millimeter-wave applications." Thesis, McGill University, 2009. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=40815.

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Integrated inductors are one of the most basic elements used in the design of modern electronic systems. However, they generally suffer from poor quality and are inherently area intensive, thus limiting system performance and prove to be a bottleneck for compact system integration. Several research efforts have been devoted to the development of miniaturized, high quality inductors. One such method proposes the use of an Artificial Magnetic Conductor (AMC) surface to enhance the inductor performance by creating a second inductive region thereby enabling inductor reuse. It can theoretically be shown, through image theory, that an AMC reflector can be used to effectively double the inductance of an inductor component. Accordingly, in order to validate this concept, two AMC surface designs are investigated for both on-chip and PCB-based implementations. The designed AMC surfaces are then integrated with standard loop inductor components in order to justify their performance benefits through measurement results of the fabricated prototypes. Finally, the practicality of this approach is demonstrated through the application of mm-wave VCOs by replacing a standard LC-VCO tank inductor with a miniaturized AMC-backed inductor. In order to do so, mm-wave LC-VCO prototypes are designed, fabricated and characterized through measurements.
Les inducteurs intégrés sont parmi les éléments élémentaires les plus utilisés dans la conception de systèmes électroniques modernes. Cependant, ils souffrent généralement d’une faible qualité et d’une large consomption d’espace, limitant ainsi les performances du système et compliquent donc l’intégration de systèmes compactes. Plusieurs efforts en recherche ont été consacrés au développement d’inducteurs de haute qualité miniatures. Une de ces méthodes proposent l’utilisation d’un Conducteur Magnétique Artificiel (CMA) comme surface pour améliorer la performance de l’inducteur en créant une deuxième région inductive ainsi permettant la réutilisation de l’inducteur. Il peut être démontré théoriquement, par la théorie des images, qu’un réflecteur CMA peut être utilisé pour doubler l’inductance total d’un inducteur. Par conséquent, afin de valider ce concept, deux designs de surfaces CMA sont investigués pour l’intégration sur puce (on-chip) et sur carte (PCB). Les surfaces CMA sont ensuite intégrées avec des composantes d’inducteurs en boucle standards afin de justifier leurs avantages en termes de performances par les résultats expérimentaux obtenus par ces prototypes. Finalement, le caractère pratique de cette approche est démontré par l’application d’un Oscillateur (VCO) d’ondes-mm en remplaçant le réservoir-LC par une version miniaturisée d’un inducteur par CMA. Pour ce faire, les prototypes d’Oscillateur-LC à ondes-mm sont conçus, fabriqués et caractérisé de façon expérimentale.

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Meng, Fanhong. "Développement d’antennes à base de structures métamatériaux pour les applications aéronautiques (GPS/DME, bande L) et de communications haut débit (en bade E – 80 GHz)." Thesis, Paris 10, 2015. http://www.theses.fr/2015PA100203.

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Les travaux présentés dans ce manuscrit sont relatifs à la conception et au développement d’antennes basées sur les structures artificielles – métamatériaux. La première antenne conçue et réalisée est une antenne bi-fonction en bande L (~1GHz) (GPS et DME) à diversité de bande/de polarisation, destinée aux applications aéronautiques. Ces travaux rentrent dans le cadre du projet MSIE (pôle de compétitivité ASTHEC) pour lequel notre LEME a été très actif. Les partenaires industriels de ce projet sont EADS/IW, Dassault aviation, INEO-Défense, SATIMO. Les résultats montrent la faisabilité d’une antenne unique pouvant avoir simultanément deux fonctions avec une diversité de polarisation et de bande spectrale. L’utilisation des métamatériaux a permis en particulier le maintien de la polarisation circulaire de l’antenne GPS -L1 à L5. La fonction DME a été consolidée avec le maintien de son gain. La seconde antenne est une antenne cavité Fabry-Pérot mettant en œuvre une structure partiellement réfléchissante double couche. Nous avons démontré le phénomène physique d’inversion de la phase du coefficient de réflexion de la PRS. Nous avons obtenu un gradient positif de phase sur une bande de 5 GHz autour de 80GHz. Grace à ce profil nouveau de la phase obtenu par la structure métamatériau PRS, on dispose d’une avance linéaire de la phase qui compense le retard du à la cavité Fabry-Pérot. Ainsi on maintient les conditions de résonance de la cavité sur une large bande, 5GHz. Nous démontrons, que la mise en œuvre de cette structure aux caractéristiques inédites permet de réaliser une antenne cavité ultra-directive sur une très large bande spectrale de 5GHz. Les performances atteintes sont une directivité de 35 à 40dBi sur 5 GHz, une adaptation parfaite (gain ~ directivité) avec très peu de sources primaires. L’antenne est compacte avec une hauteur totale inférieure au 10mm (connecteur compris) et une surface de 100mmx100mm
The work presented in this manuscript is related to the design and development of antennas based on artificial structures - metamaterials. The first designed and built antenna is a GPS and DME dual-function in the L (~ 1GHz). It is an antenna designed with polarization and spectral diversities for aeronautical applications. The work is within the MSIE project of ASTHEC cluster for which our laboratory (LEME) was very active. The industrial partners of the project are EADS/IW, Dassault Aviation, INEO-Defense SATIMO. The results show the feasibility of a single antenna having simultaneously two functions with a diversity of polarization and spectral band. The use of metamaterials enabled in particular the preservation of circular polarization of the GPS antenna on the bands ranging from L1 to L2. The DME function was consolidated with the same gain.The second antenna is an antenna Fabry-Perot cavity employing a partially reflective structure (PRS) Double-layer. We have demonstrated by numerical simulation and experimental characterization, the physical phenomenon of inversion phase of the reflection coefficient PRS. We obtain a positive gradient of the phase over a broad band of 5 GHz around 80GHz. Thanks to this new profile obtained by the PRS metamaterial structure, it has a linear advance of the phase which compensates for the delay of the Fabry-Perot cavity. Thus the cavity resonance conditions are maintained over a wide band, 5GHz. We demonstrate that the implementation of this structure with unique features allows a highly directive antenna cavity over a very wide spectral band 5GHz. The performance are a directivity of 35-40 dBi over 5 GHz, a perfect adaptation (gain ~ directivity) with very few primary sources

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Raimbault, Narcisse. "Antenne hélice compacte directive à polarisation circulaire pour dispositif RFID." Thesis, Rennes 1, 2015. http://www.theses.fr/2015REN1S009/document.

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La technologie RFID (Radio Frequency Identification) prend une place de plus en plus importante dans la société d'aujourd'hui notamment dans des domaines aussi variés que la santé, la sécurité, la logistique... Le développement de cette technologie met en évidence de nouvelles contraintes comme la réduction des zones de lecture et la géo-localisation pour le stockage et le suivi de marchandises. Dans ce contexte, la thèse s'est focalisée sur le développement d'antennes pour lecteur RFID dans le cadre du projet SPINNAKER piloté par TAGSYS RFID et soutenu par OSEO. L'objectif de cette étude est de concevoir des antennes compactes et directives à polarisation circulaire en bande UHF et SHF. L'antenne hélice présente toutes ces caractéristiques à l'exception de la hauteur, très importante dès que l'on souhaite obtenir des performances élevées surtout en gain. Dans ce manuscrit, trois solutions sont proposées pour réduire la hauteur de l'antenne hélice tout en répondant aux cahiers des charges. La première solution consiste à utiliser un réflecteur de forme cylindrique ou conique qui permet de réduire la hauteur d'une antenne hélice classique d'un facteur quatre pour atteindre 0,9λ. La réduction de la hauteur se traduit par une augmentation de la surface autour de l'antenne avec une dimension latérale de 2,3λ. La seconde solution consiste à utiliser l'antenne hélice avec une cavité Fabry-pérot. La hauteur du système antennaire obtenue est de 0,5λ avec un diamètre de 2λ. La dernière solution développée dans la thèse introduit une surface CMA à la solution précédente qui permet de réduire la hauteur à 0,25λ. Toutes les solutions proposées ont été validées expérimentalement
Over the past 20 years, the RFID (Radio Frequency Identification) technology is having a huge expansion. Nowadays, it is frequently used in different areas as the health, the security and the logistic. A lot of researches are ongoing on this topic, especially in order to reduce the reading zone of the readers and to locate the tags. This thesis focuses on the development of new antennas for Readers RFID devices and is part of the SPINNAKER project supported by OSEO. The antennas requirements are circular polarization, high directivity and gain with low profile. The helix antennas meet all these requirements except the axial length. In this manuscript, we propose three solutions to reduce the helix antenna axial length. The first one uses a cylindrical or conical optimal reflector to reduce the length by four. This reduction affects directly the surface witch increases up to 2.3λ. The second solution uses the helix antenna as a circular polarization feed for a Fabry-Perot (FP) cavity. The final antenna presents a cavity height of 0.5λ and a 2λ diameter. The last solution conserves the FP cavity in which we include an Artificial Magnetic Conductor (AMC) to reduce the cavity height to 0.25λ. All these solutions are validated by measurements

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Wang, Shenhong. "High-gain planar resonant cavity antennas using metamaterial surfaces." Thesis, Loughborough University, 2006. https://dspace.lboro.ac.uk/2134/12481.

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This thesis studies a new class of high gain planar resonant cavity antennas based on metamaterial surfaces. High-gain planar antennas are becoming increasing popular due to their significant advantages (e.g. low profile, small weight and low cost). Metamaterial surfaces have emerged over the last few years as artificial structures that provide properties and functionalities not readily available from existing materials. This project addresses novel applications of innovative metamaterial surfaces on the design of high-gain planar antennas. A ray analysis is initially employed in order to describe the beamfonning action of planar resonant cavity antennas. The phase equations of resonance predict the possibility of low-profile/subwavelength resonant cavity antennas and tilted beams. The reduction of the resonant cavity profile can be obtained by virtue of novel metamaterial ground planes. Furthermore, the EBG property of metamaterial ground planes would suppress the surface waves and obtain lower backlobes. By suppressing the TEM mode in a resonant cavity, a novel aperture-type EBG Partially Reflective Surface (PRS) is utilized to get low sidelobes in both planes (E-plane and H-plane) in a relatively finite structure. The periodicity optimization of PRS to obtain a higher maximum directivity is also investigated. Also it is shown that antennas with unique tilted beams are achieved without complex feeding mechanism. Rectangular patch antennas and dipole antennas are employed as excitations of resonant cavity antennas throughout the project. Three commercial electromagnetic simulation packages (Flomerics Microstripes ™ ver6.S, Ansoft HFSSTM ver9.2 and Designer ™ ver2.0) are utilized during the rigorous numerical computation. Related measurements are presented to validate the analysis and simulations.

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Guo, Yunchuan. "Analysis and design of novel electromagnetic metamaterials." Thesis, Loughborough University, 2006. https://dspace.lboro.ac.uk/2134/7864.

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This thesis introduces efficient numerical techniques for the analysis of novel electromagnetic metamaterials. The modelling is based on a Method of Moments modal analysis in conjunction with an interpolation scheme, which significantly accelerates the computations. Triangular basis functions are used that allow for modelling of arbitrary shaped metallic elements. Unlike the conventional methods, impedance interpolation is applied to derive the dispersion characteristics of planar periodic structures. With these techniques, the plane wave and the surface wave responses of fractal structures have been studied by means of transmission coefficients and dispersion diagrams. The multiband properties and the compactness of the proposed structures are presented. Based on this method, novel planar left-handed metamaterials are also proposed. Verifications of the left-handedness are presented by means of full wave simulation of finite planar arrays using commercial software and lab measurement. The structures are simple, readily scalable to higher frequencies and compatible with low-cost fabrication techniques.

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Kristou, Nebil. "Étude et conception de métamatériaux accordables pour la miniaturisation d’antennes aux fréquences micro-ondes." Thesis, Rennes 1, 2018. http://www.theses.fr/2018REN1S016/document.

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Les antennes présentes dans la plupart des systèmes communicants comme les véhicules automobiles, les avions et les trains se multiplient et sont soumises à une contrainte d’intégration de plus en plus sévère. De nombreuses techniques de miniaturisation d’antennes existent et passent toutes par un compromis entre la taille et les performances (bande passante et/ou rendement de rayonnement). Pour les systèmes cités ci-dessus, les antennes sont souvent placées devant ou à proximité d’un réflecteur métallique (toit de véhicule, carlingue d’aéronef). Dans ce cas, l’épaisseur de système antennaire est une contrainte majeure et les métamatériaux de type Conducteur Magnétique Artificiel (CMA) ouvrent des perspectives intéressantes grâce à leurs propriétés électromagnétiques non conventionnelles. Cependant, pour les applications sub-GHz (RFID, LTE, PMR…), les CMA sont limités par les dimensions des cellules unitaires nécessaires à leur mise en œuvre (λg/4) ainsi que leur bande réduite de fonctionnement. Réduire leurs dimensions permet de rendre leur utilisation compatible avec le contexte des antennes miniatures intégrées. Ajouter l’agilité fréquentielle permet de palier le problème de la bande passante réduite dans le cas des antennes et des CMA miniaturisés en ajustant le fonctionnement du système antennaire sur une large bande passante. Cette thèse de doctorat propose d’étudier et de développer un nouveau système antennaire à faible profil composé d’une antenne miniature associée à une métasurface compacte reconfigurable en fréquence et compatible avec le standard NB-IoT dans la bande basse LTE (700 MHz – 960 MHz)
Antennas are now very integrated in several connected systems like cars, airplanes and trains. Many antenna miniaturization techniques exist and all go through a compromise between size and performance (bandwidth and/or radiation efficiency). For the systems mentioned above, the antennas are often placed near a metallic reflector (vehicle roof, aircraft cabin). Within this context, Artificial Magnetic Conductors (AMC) present an attractive reflector for low profile antennas which can take advantage of intrinsic zero reflection phase response to boost antenna performance without the need for thick quarter wave backplane. However, for sub-GHz applications (RFID, LTE, PMR ...), AMC are limited by the size of the unit cells necessary for their implementation (λg/4) as well as their reduced operating bandwidth. AMC miniaturization makes their use compatible with small antennas. Adding tunability restores the possibility of adjusting the operating frequency over a large bandwidth. This PhD thesis proposes to study and develop a new electrically small, low-profile antenna based on miniaturized and tunable AMC for the NB-IoT standard in low LTE band (700 MHz – 960 MHz)

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Cooper, James Roger. "Novel wireless sensor configurations incorporating isotropic radiators on conformal artificial magnetic conductors." Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/52246.

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The objective of the presented research is to develop a novel, ink-jet printed, chipless, passive, wireless sensor topology, which can radiate in a near isotropic pattern without interference from embedded devices, for use in dispersed sensor networks. This objective includes the development of a hardware based, uniquely identifiable, collision avoidance communication method, and an integrated sensor system that is easily integrated into the topology. Wireless sensor networks can be and are used in military, medical and industrial applications; and the demand for them is ever growing. However, current sensor networks have various trade-offs and limitations, including cost, number of distinguishable nodes, and ease of manufacturing. These trade-offs lead to unique sensors needing to be designed for each situation. To develop a widely used module, a topology must be developed that can meet as many demands as possible with fair tradeoffs. Many of the above proposed criteria for the topology are already integrated into RFID technology. Therefore, much of the research is the application and advancement of current RFID technology for the purpose of designing the topology. The research begins with the theory and design of conformal artificial magnetic conductors, which is used in the design of a near isotropic radiator and isolated core for device embedding. Then, novel fabrication techniques will be investigated and deployed in the fabrication of the topology. Next, a novel "smart skin" sensor is developed which is easily integrated into the desired fabrication technique. Finally, an anti-collision RFID circuit for on-tag placement, which is based on frequency-doubling transceivers, is designed, which can also be easily integrated into the final topology. This module is designed for use with a variety of different sensors. This versatility gives it ruggedness for use in many different environments. For proof of concept, this topology is fabricated and tested against current commercially sold tags. Through the design and testing of the radiator, circuitry, and embedded sensors, it is shown that this design is a suitable topology for use in many different environments and applications.

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Silva, Pimenta Marcio. "Antennes souples à base de métamatériaux de type conducteurs magnétiques artificiels pour les standards de systèmes de géolocalisation." Phd thesis, Université Nice Sophia Antipolis, 2013. http://tel.archives-ouvertes.fr/tel-00923200.

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Grâce aux progrès réalisés ces dernières années dans la conception de réseaux intelligents, tels que les réseaux centrés sur la personne (WBAN) ou les réseaux sans fils de proximité (WPAN), de nouveaux types d'applications émergent et utilisent des capteurs d'informations capables de relever les paramètres physiologiques, environnementaux et plus particulièrement le positionnement des personnes. Dans ce cadre, nous nous sommes attachés dans ce travail de recherche à la conception et la réalisation d'antennes en polarisation circulaire pouvant être intégrées dans des vêtements, pour les standards de géolocalisation européen Galiléo et Américain GPS. Nous avons utilisé pour ces antennes des structures métamatériaux de type conducteurs magnétiques artificiels, afin d'augmenter les performances en rayonnement et pour diminuer le couplage avec et le corps humain. Une autre voie explorée est l'utilisation d'antennes patchs qui sont de nature faible encombrement. La bande de fréquence du standard de communications par satellite Iridium étant très proche du standard de géolocalisation GPS, nous avons trouvé intéressant de développer une solution de type patch couvrant les deux bandes GPS (1,575 GHz) et Iridium (1,621 GHz). L'antenne devant être intégrée sur une boite crânienne, les niveaux de débit d'absorption spécifique et les modifications du rayonnement sous conformation de l'antenne ont également été étudiés. L'évolution de ce travail a été ensuite d'étudier le comportement de cette antenne posée sur le dessus d'un casque militaire français. Les performances en rayonnement ont été satisfaisantes et ont montré la possibilité d'une telle application.

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Presse, Anthony. "Conception d'antennes souples et de conducteurs magnétiques artificiels en bande UHF." Thesis, Rennes 1, 2015. http://www.theses.fr/2015REN1S087/document.

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L'invention de l'antenne fût à la base de la création des communications sans fil à l'orée du XXe siècle. A l'origine des objets métalliques destinés à transmettre et recevoir des ondes électromagnétiques, les antennes n'ont cessé de se complexifier pour satisfaire l'impressionnant développement des communications sans fil. C'est dans ce contexte qu'est né le concept d'antenne « wearable » il y a moins de deux décennies ouvrant un nouveau champ de recherche sur les antennes souples. C'est dans ce cadre que ce travail de thèse se consacre à la conception d’antennes souples en bande UHF.Une première étude a permis de concevoir une antenne Vivaldi antipodale [150 - 900 MHz] souple pour la Section Technique de l'Armée de Terre. Six de ces antennes sont destinées à être placées sous un ballon gonflé à l'hélium pour réceptionner des signaux RF.Une seconde étude est effectuée en collaboration avec la société Syrlinks et le CNES. L'objectif du projet est de concevoir des antennes souples pour le suivi de personnes avec le système ARGOS (401 et 466 MHz). La solution retenue est une PIFA planaire de largeur inférieure à lambda/3. Elle a l'avantage d'être fine et légère. Le matériau souple employé est un caoutchouc silicone sélectionné parmi plusieurs matériaux souples grâce à des caractérisations diélectriques. Cependant, le problème de cette antenne est qu'elle possède un rayonnement quasi-omnidirectionnel. Etant donné qu'il n'était pas envisageable d'utiliser un plan réflecteur métallique pour des raisons de dimensions, il a été décidé de concevoir un conducteur magnétique artificiel (CMA) souple. Toutefois, la conception de CMA dans le bas de la bande UHF se heurte à des difficultés de miniaturisation. Pour contourner ce problème, il a été développé deux concepts de CMA à cellules unitaires de faibles dimensions devant la longueur d'onde. La première solution utilise des capacités interdigitées et la seconde une structure double couche. Pour ces deux concepts, un modèle circuit est proposé et validé par des mesures expérimentales. Les mesures de l'association CMA - antenne montrent une bande passante suffisante pour des applications ARGOS et un rayonnement majoritairement dirigée dans la direction opposé à celle du CMA
The invention of antennas was the base of wireless communications appearance at the dawn of the twentieth century. Originally metal objects for transmitting and receiving electromagnetic waves, antennas have steadily become more complex to meet the impressive development of wireless communications. It is in this context that the concept of wearable antennas was born less than two decades ago opening a new field of research namely flexible antennas. It is in this framework that this thesis is dedicated to the design of flexible antennas for UHF band.A first study enabled the design of a flexible antipodal Vivaldi antenna [150-900 MHz] for Technical Section of the Army. Six of these antennas are intended to be placed under a balloon inflated with helium for receiving RF signals.A second study was conducted in collaboration with the company Syrlinks and CNES. The objective of the project is to design flexible antennas for tracking people with ARGOS system (401 and 466 MHz). The selected solution is a planar PIFA which width is smaller than lambda/3. This antenna has the advantage of being thin and light. The flexible material used is a silicone rubber and it was selected among several others due to some dielectric characterizations. However, the drawback of this antenna is that it has a quasi-omnidirectional radiation pattern. Since it was not possible to use a reflector metal plane due to size constraints, it was decided to design a flexible artificial magnetic conductor (AMC). However, the design of AMCs in the lower UHF band is challenged with the miniaturization difficulties. Two concepts of small size (compared to the wavelength) AMCs unit cells were developed to work around this problem. The first solution uses interdigitated capacitors and the second a double layer structure. For these two concepts, a circuit model is proposed and validated by experimental measurements. The measurement of the AMC associated antenna demonstrates a bandwidth sufficient for ARGOS applications and a radiation pattern mostly directed in the direction opposite to that of the AMC

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Ayad, Houssam. "Antenna Performance Control using Metamaterials." Thesis, Grenoble, 2012. http://www.theses.fr/2012GRENT013/document.

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Le travail de cette thèse est en rapport avec les métamatériaux et ses applications. Tout d’abord, un état de l’art est dressé en présentant leur évolution depuis leur apparition en 19ème siècle jusqu’au nos jours. Les notions sur les milieux chirale, bi-anisotrope, cristaux photoniques et quelques applications dans ces milieux sont données. Ensuite, nous présentons les équations classiques de Maxwell dans les milieux complexes. L’effet bi-anisotrope dans les métamatériaux est ensuite validé par l’extraction des paramètres caractéristiques du matériau main gauche (LHM). La validation a été faite en utilisant deux types différents du résonateur avec inclusion (SRR). Les métamatériaux sont également étudiés comme des cristaux photoniques quand les dimensions utilisées sont de l’ordre de la longueur d’onde correspondant.De plus, les résonateurs SRR et multi-SRR sont analysés du point de vue analytique et électromagnétique afin d’extraire leur fréquence de résonance. Par conséquent, ces composants peuvent être introduits dans différents types de conception; La surface conductrice magnétique artificielle (AMC) illustre un cas explicite et efficace de ces derniers. Une antenne dipôle, placée sur cette surface à la place d’un plan de masse conventionnel, a été étudiée comme une application des métamatériaux. Les résultats relatifs sur la directivité, le gain et le coefficient de réflexion montrent une nette amélioration. Une antenne multi-bandes, comme une autre application des métamatériaux, a également été conçue et simulée. Le résonateur SRR est inséré dans l’antenne de départ afin de créer une autre résonance, et par conséquent une autre bande est ainsi créée
The work in this thesis deals with metamaterials, its components and applications. A historical overview about these materials, features and researches in the domain are presented. Chiral media, binaisotropic materials and photonic crystals are also studied in order to visualize physics behind metamaterials.Electromagnetic properties in complex media are widely investigated. Starting from Maxwell’s equations, bi-anisotropic materials and their effect are deeply analyzed whereas two types of Split Ring Resonator (SRR) are treated to determine constitutive parameters of Left Handed Materials (LHM). The metamaterials are also studied as photonic crystals since the effective medium approach is not applicable when the dimensions of the inclusions tend to the operating wavelength.Moreover, SRRs and Multi SRRs are synthesized analytically and electromagnetically in order to extract their resonant frequencies. Consequently, these components could be introduced in any design; Artificial Magnetic Conductor (AMC) surface is an efficient case. Thus, a low profile antenna positioned over such surface is examined as an application of metamaterials. The results of directivity, gain and reflection coefficient are of great importance and affirm the employing of metamaterials in such applications. A dual band PCB antenna, as another application of metamaterials, is designed and simulated. The SRR element studied in the previous chapters is used as the trap which inserted in the arm of the antenna in order to create another resonance, and consequently another band is created

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Peng, Guan-Fu, and 彭冠富. "Design of a Novel Artificial Magnetic Conductor." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/60437937815906937556.

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碩士
國立彰化師範大學
電信工程研究所
97
In this thesis, we propose a novel artificial magnetic conductor(AMC) structure using wire helix in a metal box. This structure is equivalent to a parallel resonant LC circuit resulting in some kinds of characteristics like the perfect magnetic conductor(PMC) at resonance frequency. Due to the periodic arrangement of this structure, the electromagnetic band-gap(EBG) effect will appear in this specific band. First, we calculate the effective AMC bandwidth with reflection phase between 45 degrees for AMC with infinite elements case by a numerical analysis model. Simulated radiation patterns for half-wavelength dipole antenna on the AMC is compared with those of the same half-wavelength dipole antenna on the PMC. Our proposed AMC structure is verified to have the characteristics of PMC from 1.95 GHz to 2.75 GHz. We also study the characteristics of EBG of this AMC structure by suspended microstrip method. One of the measured EBG band is from 2.765 GHz to 2.934 GHz.

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Hsu, Sheng-Chieh, and 許勝傑. "Reflection Characteristics of a Gradient Artificial Magnetic Conductor." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/37128951384019539623.

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碩士
國立交通大學
電信工程研究所
99
We studied the electromagnetic reflection of a two-dimensional square patches array backed with a grounded dielectric slab. By tuning the size of the metal patch, the adjacent two patches may have an equal reflected-phase angle. Using this property of progressively reflected-phase angle in the array elements, for a normal incident wave we can steer the reflected wave into a desired direction. In this thesis, we have established a simple formula based on the array antenna theory to figure out the reflected wave pattern. Moreover, a time-domain full-wave simulation package (CST) was employed to rigorously calculate the electromagnetic fields in the structure as well as the far-field pattern. Besides, we have fabricated the structure and measured its scattering pattern in an electromagnetic anechoic chamber. The excellent measured results confirm the design principle and procedures in this research. Such a planar structure may have potential applications in beam-tilting and radar cross section reduction.

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15

Kern, Douglas John Werner Douglas H. "Advancements in artificial magnetic conductor design for improved performance and antenna applications." 2009. http://etda.libraries.psu.edu/theses/approved/WorldWideIndex/ETD-4373/index.html.

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16

Yang, Cheng-Yan, and 楊承諺. "Design of Tag Antennas with Artificial Magnetic Conductor for On-Body Applications." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/97448130247265925963.

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碩士
國立宜蘭大學
電子工程學系碩士班
104
This thesis aims at designing UHF RFID tag antennas with artificial magnetic conductor and a circularly polarized(CP) antenna for on-body applications. UHF radio frequency identification (RFID) technology is capable of being used to monitor and identify objects or people. By using backscattering modulation to communicate between a reader and tags, UHF RFID has a relatively far reading range, quick data transferring rate, large data carrying capacity and other advantages. However, when on-body applications are required, the input impedance, radiation pattern, realized gain and reading range of tags are influenced due to human-body dissipations effect. Here, two kinds of artificial magnetic conductor placed on the back plane of a miniaturized dipole tag are studied in order to insulate the influence from the human body. The designed tag antennas with artificial magnetic conductor can operate in the UHF RFID band (902-928 MHz). In this thesis, a unit cell of a patch-type artificial magnetic conductor (AMC) is proposed in the beginning. The unit cell size of the AMC is 55×55 mm2(0.168λ0 × 0.168λ0 mm2). To miniaturize the AMC size and lower the first resonant frequency, four T-type slots are symmetrically inserted into each side of the metal patch so that the operating frequency is reduced to 915 MHz. The second kind of unit cell structure for the miniaturized AMC is then proposed. This kind of AMC has capacitive interdigital structures which are the key design factor for designing smaller unit cells at the low operating frequency. The size of the unit cell is shrunk to 40×40 mm2 (0.122λ0 × 0.122λ0 mm2). On the other hand, a T-matching network is employed to transform the impedance of a folded dipole to conjugate match with a Monza®4 microchip. The proposed antennas are analyzed and designed in free space. The designed tag antenna is simulated by the EM simulator, HFSS. The simulation results are compared with those by the FEKO EM simulator to verify numerical accuracy. Finally, the design structure is also constructed to verify the simulation results. In the third chapter, two kinds of tag antenna with AMC are presented and discussed. One is the folded dipole antenna with T-slot AMC and the other is the dipole antenna with miniaturized AMC. The bandwidth, gain and radiation efficiency are analyzed as the influence of body proximity is considered. The proposed antennas with AMC are fabricated to perform measurement. The reading range can achieve up to 8 meters when the tag is put close to the human body. In chapter 4, a miniaturized CP tag antenna is proposed in order to improve the reading range. Theoretically, a circularly polarized antenna does not have 3 dB polarization losses as compared with a linear tag antenna since a UHF reader always radiates a CP wave. A cross-coupled CP-tag antenna which has a symmetric matching network is presented and studied. Two asymmetrically orthogonal cross-dipoles with meander lines are combined to generate a degenerate mode for circular polarization. The geometry size of the proposed tag is only 60×60 mm2. In the free space, the simulated impedance bandwidth of the CP tag antenna achieves 82 MHz (893-974 MHz, 8.6 %), the 3dB band-width is 16 MHz (916-930 MHz, 1.5 %), and the realized gain is 1.95 dBic, which make it achieve a 12 m reading range.

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17

Han-LinYue and 岳翰林. "Research on Millimeter-Wave CMOS On-Chip Antennas and Artificial Magnetic Conductor (AMC) Antennas." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/18268790475031752540.

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18

Nafe, Mahmoud. "Gain-Enhanced On-Chip Antenna Utilizing Artificial Magnetic Conductor Reflecting Surface at 94 GHz." Thesis, 2015. http://hdl.handle.net/10754/565638.

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Nowadays, there is a growing demand for high frequency-bandwidth mm-wave (30-300 GHz) electronic wireless transceiver systems to support applications such as high data-rate wireless communication and high resolution imaging. Such mm-wave systems are becoming more feasible due to the extreme transistor downscaling in silicon-based integrated circuits, which enabled densely-integrated high-speed elec- tronics operating up to more than 100 GHz with low fabrication cost. To further enhance system integrability, it is required to implement all wireless system compo- nents on the chip. Presently, the last major barrier to true System-on-Chip (SoC) realization is the antenna implementation on the silicon chip. Although at mm-wave frequencies the antenna size becomes small enough to fit on chip, the antenna performance is greatly deteriorated due the high conductivity and high relative permittivity of the silicon substrate. The negative e↵ects of the silicon substrate could be avoided by using a metallic reflecting surface on top of silicon, which e↵ectively isolates the antenna from the silicon. However, this approach has the shortcoming of having to implement the antenna on the usually very thin silicon oxide layer of a typical CMOS fabrication process (10’s of μm). This forces the antenna to be in a very close proximity (less than one hundredth of a wavelength) to the reflecting surface. In this regime, the use of conventional metallic reflecting surface for silicon shielding has severe e↵ects on the antenna performance as it tends to reduce the antenna radiation resistance resulting in most of the energy being absorbed rather than radiated. In this work, the use of specially patterned reflecting surfaces for improving on- chip antenna performance is investigated. By using a periodic metallic surface on top of a grounded substrate, the structure can mimic the behavior of a perfect mag- netic conductor, hence called Artificial Magnetic Conductor (AMC) surface. Unlike conventional ground plane reflecting surfaces, AMC surfaces generally enhance the radiation and impedance characteristics of close-by antennas. Based on this property, a ring-based AMC reflecting surface has been designed in the oxide layer for on-chip antennas operating at 94 GHz. Furthermore, a folded dipole antenna with its associ- ated planar feeding structures has been optimized and integrated with the developed ring-based AMC surface. The proposed design is then fabricated at KAUST clean- room facilities. Prototype characterization showed very promising results with good correlation to simulations, with the antenna exhibiting an impedance bandwidth of 10% (90-100 GHz) and peak gain of -1.4 dBi, which is the highest gain reported for on-chip antennas at this frequency band without the use of any external o↵-chip components or post-fabrication steps.

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19

HONG, JHIH-HAN, and 洪志翰. "Design of Circularly Polarized Tag Antenna with Artificial Magnetic Conductor for On-Body Applications." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/422486.

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碩士
國立宜蘭大學
電子工程學系碩士班
105
This thesis aims at designing UHF tag antennas with artificial magnetic conductor (AMC) for on-body UHF RFID applications. RFID technology has extensive applications in the world markets. In the development of the IOT, there will be various kinds of object using tag antennas to transfer information. Even in case of developing for on-body applications, the wearable device or tags will be indispensable. Whenever the tag is applied on the different objects, the performance of the tag will be changed by the material of object. Designers must seriously consider the object effects on the RFID tags. If the object is a lossy media, the antenna gain will significantly decrease. Therefore, we designed various tag antennas with artificial magnetic conductor. When the tag antenna is pasted on a human body or metal objects, AMC can effectively isolate the bad effects and then read range is increased in the applications. In the thesis, we used the concept of the PDAMC (Polarization-dependent artificial magnetic conductor) to convert the linearly polarized tag dipole into the circularly polarized (CP) tag. The PDAMC makes the tag reduce the polarization loss of 3 dB for CP reader applications and it also insulate the interference of human body. Thus, the dipole tag has farther read range and its predicted read range can achieve 16 meters. Our research results demonstrate that the tags antenna can be completely pasted on the AMC surface to achieve the design of the thinnest thickness. The study of circularly polarized antennas is more complex than linear polarized antennas in the field of the AMC research. We proposed a CP cross-dipole tag which was integrated on a square AMC structure. The substrate of the cross-dipole can be pasted on the surface of a 3×3 AMC to achieve the goal of thin thickness. The total thickness is only 6.4 mm. For on-body applications, the read range of the CP tag was significantly increased by the AMC substrate. The read range of 15.7 meters was measured by using a reader of 4W EIRP when the tag was pasted on a human body. In order to develop a wearable antenna for on-body applications, we also explored the design by using latex substrate which is a flexible material. Since the latex substrate has features of low weight, flexible and non-absorbent, the CP tag was designed directly on the AMC latex substrate. The study finds that the predicted read range achieves 17.5 meters but the size is a little large. Furthermore, the number of the AMC array was further reduced to miniaturize the array size. The CP cross-slot antenna was integrated with a 2×2 AMC structure to achieve the smallest area which is only 131×131×6.4 mm3. In addition to reducing the numbers of AMC array, the proposed miniaturized AMC was designed by using cross-slots cut on the conduct of a unit cell AMC. When the tag is integrated on the miniaturized 3×3 AMC, the read range achieves around 10.8 meters.

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20

"High Impedance Surface Using A Loop With Negative Impedance Elements." Master's thesis, 2010. http://hdl.handle.net/2286/R.I.8791.

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abstract: Antennas are required now to be compact and mobile. Traditional horizontally polarized antennas are placed in a quarter wave distance from a ground plane making the antenna system quite bulky. High impedance surfaces are proposed for an antenna ground in close proximity. A new method to achieve a high impedance surface is suggested using a metamaterial comprising an infinite periodic array of conducting loops each of which is loaded with a non-Foster element. The non-Foster element cancels the loop's inductance resulting in a material with high effective permeability. Using this material as a spacer layer, it is possible to achieve a high impedance surface over a broad bandwidth. The proposed structure is different from Sievenpiper's high impedance surface because it has no need for a capacitive layer. As a result, however, it does not suppress the propagation of surface wave modes. The proposed structure is compared to another structure with frequency selective surface loaded with a non-Foster element on a simple spacer layer. In particular, the sensitivity of each structure to component tolerances is considered. The proposed structure shows a high impedance surface over broadband frequency but is much more sensitive than the frequency selective surface structure.
Dissertation/Thesis
M.S. Electrical Engineering 2010

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21

Yung-HsiagnChuang and 莊詠翔. "Research on 60- and 77-GHz GIPD On-Chip Antenna / Filtering-Antennas and CMOS Artificial Magnetic Conductor (AMC) Antennas." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/23845646976160362070.

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碩士
國立成功大學
電腦與通信工程研究所
100
This thesis presents the design of millimeter-wave (MMW) GIPD and CMOS on-chip antennas. The GIPD and CMOS MMW on-chip antennas are fabricated with tMt GIPD process and TSMC 90-nm CMOS standard process, respectively. The three-dimensional (3D) EM simulator HFSS is used for design simulation. The designed MMW on-chip antennas including: (1) a 77-GHz GIPD integrated on-chip Yagi antenna with balun-bandpass filter, which combined three passive components (antenna, balun, bandpass filter) of the MMW receiver front-end; (2) a 77-GHz CMOS integrated on-chip AMC-Yagi antenna with balun-bandpass filter, in which an artificial magnetic conductor (AMC) between antenna and Si-substrate is placed to improve radiation efficiency; (3) a 77-GHz GIPD integrated on-chip linear tapered slot antenna (LTSA) with unbalanced-to-balanced bandpass filter, in which two sides of the LTSA are corrugated with rectangular gratings to increase the antenna power gain and F/B ratio; (4) a 60-GHz unbalanced-fed bandpass-filtering dipole/Yagi antennas with bandpass response. The measured performances of the designed MMW on-chip antennas are all performed by using the on-wafer measurement setup.

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22

YiWu and 吳易. "60- and 77-GHz Millimeter-Wave CMOS On-Chip Artificial-Magnetic-Conductor Antennas and Integrated Phased-Array Antenna RFIC." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/h99u3g.

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碩士
國立成功大學
電腦與通信工程研究所
102
This thesis presents the research of millimeter-wave (MMW) CMOS on-chip antennas fabricated using TSMC 90-nm and 0.18-μm CMOS standard process. The three-dimensional (3D) EM simulator HFSS is used for design and simulation. The designed MMW on-chip antennas including: (1) a 60-GHz CMOS integrated on-chip artificial-magnetic-conductor (AMC) spiral monopole-antenna with compact folded loop dual-mode bandpass filter; (2) a 60-GHz CMOS AMC bandpass-filtering spiral monopole-antenna; (3) a 77-GHz CMOS AMC 1×2 folded dipole antenna array; (4) a 60-GHz CMOS AMC 2×2 monopole-antenna phased array receiving subsystem with integrated aariable-gain low-noise amplifier (VG-LNA) and phase shifter. The AMC structures are utilized in the designed on-chip antenna to reduce the CMOS substrate loss and improve radiation efficiencies. The measured performances of the designed MMW on-chip antennas are all conducted by the on-wafer measurement setup.

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23

Huang, Chien-Jung, and 黃建融. "Formulation of a Standard Flow Chart of Feeding the Low Profile Antenna and Extraction of the Artificial Magnetic Conductor Band from the Reflection Phases." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/97925226528887092232.

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碩士
國立交通大學
電信工程研究所
102
A popular way to design a low profile antenna is by combining the traditional antenna with a high impedance surface (HIS), because the HIS can mimic the property of the perfect magnetic conductor (PMC) to improve the radiation. However, the way to feed the low profile antenna is still a big issue because the artificial magnetic conductor (AMC) condition of the HIS is a frequency-dependent property. It means the frequency band in which the PMC property of the HIS prevails is limited. This band is termed as the AMC region. There had been intensive research performed on the low profile antenna but there has not been a consistent, let alone identical method for feeding the low profile antenna. In consideration of that, matching the low profile antenna by a systematic way is our purpose. To fulfill our idea, we should introduce the reflection phase first, because when talking about the HIS structure, many researchers usually characterize the AMC region of the HIS by the frequency range in which the reflection phase lies between ±45° (0° of reflection phase pertains to PMC property). However, this does not consider the radiation pattern of the traditional antenna. Because the reflection phase of the general definition is defined by the normal incident wave, the waves excited by the traditional antenna on the HIS are not all normal incident waves toward the HIS. Therefore surveying the pattern of the traditional antenna becomes the priority to extract the AMC band.

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24

Alibakhshikenari, M., B. S. Virdee, C. H. See, Raed A. Abd-Alhameed, F. Falcone, and E. Limiti. "High-gain metasurface in polyimide on-chip antenna based on CRLH-TL for sub-terahertz integrated circuits." 2020. http://hdl.handle.net/10454/17985.

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Yes
This paper presents a novel on-chip antenna using standard CMOS-technology based on metasurface implemented on two-layers polyimide substrates with a thickness of 500 μm. The aluminium ground-plane with thickness of 3 μm is sandwiched between the two-layers. Concentric dielectric-rings are etched in the ground-plane under the radiation patches implemented on the top-layer. The radiation patches comprise concentric metal-rings that are arranged in a 3 × 3 matrix. The antennas are excited by coupling electromagnetic energy through the gaps of the concentric dielectric-rings in the ground-plane using a microstrip feedline created on the bottom polyimide-layer. The open-ended feedline is split in three-branches that are aligned under the radiation elements to couple the maximum energy. In this structure, the concentric metal-rings essentially act as series left-handed capacitances CL that extend the effective aperture area of the antenna without affecting its dimensions, and the concentric dielectric rings etched in the ground-plane act as shunt left-handed inductors LL, which suppress the surface-waves and reduce the substrates losses that leads to improved bandwidth and radiation properties. The overall structure behaves like a metasurface that is shown to exhibit a very large bandwidth of 0.350–0.385 THz with an average radiation gain and efficiency of 8.15dBi and 65.71%, respectively. It has dimensions of 6 × 6 × 1 mm3 that makes it suitable for on-chip implementation.
This work is partially supported by RTI2018-095499-B-C31, Funded by Ministerio de Ciencia, Innovación y Universidades, Gobierno de España (MCIU/AEI/FEDER,UE), and innovation programme under grant agreement H2020-MSCA-ITN-2016 SECRET-722424 and the fnancial support from the UK Engineering and Physical Sciences Research Council (EPSRC) under grant EP/E022936/1.
Research Development Fund Publication Prize Award winner, March 2020

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25

"Flexible, Reconfigurable and Wearable Antennas Integrated with Artificial Magnetic Conducting Surfaces." Doctoral diss., 2017. http://hdl.handle.net/2286/R.I.45935.

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abstract: Flexibility, reconfigurability and wearability technologies for antenna designs are presented, investigated and merged in this work. Prior to the design of these radiating elements, a study is conducted on several flexible substrates and how to fabricate flexible devices. Furthermore, the integration of active devices into the flexible substrates is also investigated. A new approach of designing inkjet-printed flexible reconfigurable antennas, based on the concept of printed slot elements, is proposed. An alternate technique to reconfigure the folded slot antenna is also reported. The proposed radiator works for both Wireless Local Area Network (WLAN) and Worldwide Interoperability for Microwave Access (WiMAX) applications. The flexible reconfigurable antenna is also redesigned to resonate at both (2.4/5.2 GHz) for WLAN devices and its Multiple-Input Multiple-Output (MIMO) configuration is reported. Two orthogonal elements are used to form the MIMO antenna system for better isolation. The wearability of the proposed flexible reconfigurable radiator is also discussed. Since wearable antennas operate close to the human body, which is considered as a lossy tissue, an isolation between the radiating elements and human body is required to improve the radiation characteristics and to reduce the Specific Absorption Rate (SAR). The proposed antenna is redesigned on an Artificial Magnetic Conductor (AMC) surface that also functions as a ground plane to isolate the radiator from the human body. To examine its performance as a body-worn device, it is measured at different positions on the human body. Furthermore, simulations show that the SAR level is reduced when using the AMC surface. The proposed wearable antenna works for both Wireless Body Area Network (WBAN) and WiMAX body-worn wireless devices. Electromagnetic bandgap (EBG) structures are used to suppress surface wave propagation in printed antennas. However, due to the presence of vias, not all of them can be utilized in flexible radiators. Thus, a Perforated High Impedance Surface (PHIS) is proposed which suppresses the surface waves without the need of vias, and it also serves as a ground plane for flexible antennas. The surface wave suppression and the antenna applications of the proposed PHIS surface are discussed.
Dissertation/Thesis
Doctoral Dissertation Electrical Engineering 2017

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26

Yu, Yiyang. "Ultra-Thin AMC for Gain-Enhancement of a 94 GHz Antenna-On-Chip." Thesis, 2021. http://hdl.handle.net/10754/668985.

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The surge in transistor scaling and integration processes has driven the growth of wireless technology, especially low-cost millimeter-wave systems. Based on mainstream Silicon technology, System-on-Chip (SoC) has become an attractive approach to achieve the required high level of on-chip integration for modern wireless systems. However, the low resistivity (ρ=10 Ω-cm) and high relative permittivity (εr=11.9) of the silicon substrate are unsuitable for hosting antennas on it, because the Radio Frequency (RF) power is lost in the lossy silicon substrate, and some of it gets radiated in a certain undesired direction due to the surface waves. This has caused such antennas, typically known as Antenna-on-chip (AoC), to be poor radiators. Introducing an on-chip artificial magnetic conductor (AMC) between the substrate and the antenna can isolate the silicon substrate from the antenna and provide in-phase reflection, thereby improving the radiation performance. However, the drawback of conventional on- chip AMC is its relatively large thickness, which is extremely difficult to achieve on the thin silicon dioxide layer of typical CMOS processes (~10-15 μm). To resolve this problem, the embedded guiding structures have been designed between the periodic structure layer and the ground plane to realize an ultra-thin AMC which is suitable for thin oxide stack up of typical CMOS processes. Specifically, a patch-based AMC with embedded guiding structures has been designed for an on-chip monopole antenna operating at 94 GHz. The performance of the AMC has been studied for different resistivity substrates (from 10-3 to 103 Ω-cm). The AMC-backed on- chip antenna has been fabricated through an in-house CMOS-compatible process. The adhesion of the metallic layer to the substrate has been improved without using a seed layer, which is typically a low conductivity metal and has a negative impact on the radiation of the AoC. The measured input impedance and radiation performance of the AMC-backed AoC are fairly consistent with the simulations. It provides 5.85 dBi gain with the return loss of 16 dB at 94 GHz. According to the author’s best knowledge, this is the thinnest AMC-based AoC design in the literature.

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27

"Metasurface-Based Techniques for Broadband Radar Cross-Section Reduction of Complex Structures." Doctoral diss., 2020. http://hdl.handle.net/2286/R.I.62941.

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abstract: Within the past two decades, metasurfaces, with their unique ability to tailor the wavefront, have attracted scientific attention. Along with many other research areas, RADAR cross-section (RCS)-reduction techniques have also benefited from metasurface technology. In this dissertation, a novel technique to synthesize the RCS-reduction metasurfaces is presented. This technique unifies the two most widely studied and two well-established modern RCS-reduction methods: checkerboard RCS-reduction andgradient-index RCS-reduction. It also overcomes the limitations associated with these RCS-reduction methods. It synthesizes the RCS-reduction metasurfaces, which can be juxtaposed with almost any existing metasurface, to reduce its RCS. The proposed technique is fundamentally based on scattering cancellation. Finally, an example of the RCS-reduction metasurface has been synthesized and introduced to reduce the RCS of an existing high-gain metasurface ground plane. After that, various ways of obtaining ultrabroadband RCS-reduction using the same technique are proposed, which overcome the fundamental limitation of the conventional checkerboard metasurfaces, where the reflection phase difference of (180+-37) degrees is required to achieve 10-dB RCS reduction. First, the guideline on how to select Artificial Magnetic Conductors (AMCs) is explained with an example of a blended checkerboard architecture where a 10-dB RCS reduction is observed over 83% of the bandwidth. Further, by modifying the architecture of the blended checkerboard metasurface, the 10-dB RCS reduction bandwidth increased to 91% fractional bandwidth. All the proposed architectures are validated using measured data for fabricated prototypes. Critical steps for designing the ultrabroadband RCS reduction checkerboard surface are summarized. Finally, a broadband technique to reduce the RCS of complex targets is presented. By using the proposed technique, the problem of reducing the RCS contribution from such multiple-bounces simplifies to identifying and implementing a set of orthogonal functions. Robust guidelines for avoiding grating lobes are provided using array theory. The 90 degree dihedral corner is used to verify the proposed technique. Measurements are reported for a fabricated prototype, where a 70% RCS-reduction bandwidth is observed. To generalize the method, a 45 degree dihedral corner, with a quadruple-bounce mechanism, is considered. Generalized guidelines are summarized and applied to reduce the RCS of complex targets using the proposed method.
Dissertation/Thesis
Doctoral Dissertation Electrical Engineering 2020

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