Dual-polarized, broadband metasurface cloaks for antenna applications

A communication system that reduces the mutual influence of antennas operating in similar or different frequency bands. The communication system includes a first and a second antenna operating in a first and a second frequency band, respectively, and placed in close proximity to each other. The first antenna is covered by a conformal mantle metasurface with anti-phase scattering properties thereby cancelling the scattering in the second frequency band. The conformal mantle metasurface consists of a patterned metallic sheet comprising slits both in an azimuthal and a vertical direction to reduce both vertical and horizontal polarization scattering. When the first antenna is a low-band dipole antenna and when the second antenna is a high-band dipole antenna, the conformal mantle metasurface reduces the low-band blockage without disrupting the performance of both antennas in terms of radiation pattern and impedance matching.Board of Regents, University of Texas Syste

Tunable antenna design by metamaterial structures operating at S band

Un “metamaterial” por su definición ampliamente aceptada es una estructura construida artificialmente que obtiene sus propiedades materiales de su estructura en lugar de la composición de su material intrínseco. El ámbito de los materiales ha ganado mucha atención dentro de la comunidad científica en la última década. Con los continuos avances y descubrimientos conducen al camino de las aplicaciones prácticas; los metamateriales han ganado la atención de las empresas de base tecnológica y los organismos de defensa interesados en el uso de dispositivos de próxima generación. Las superficies selectivas en frecuencia (FSS) son una variedad potente de metamateriales que, dependiendo de la geometría de la superficie, se pueden utilizar para diseñar propiedades de radiación específicas tales como la emisión direccional, emisión polarizada circular y lineal, y la selectividad espectral. Los elementos de la FSS pueden ser tanto elementos metálicos sólidos como elementos metálicos con aberturas, y en los diseños tradicionales, la superficie selectiva en frecuencia (FSS) normalmente opera en torno a la resonancia de media longitud de onda de los elementos. En este proyecto se va a utilizar una superficie selectiva de frecuencia (FSS) con el fin de realizar metamateriales sintonizables -una amplia clase de metamateriales controlables diseñados artificialmente, y desarrollar una antena sintonizable que trabaje a 2.4 GHz. La FSS consiste en una serie de elementos rectángulos cargados con varactores y capacitores con una película delgada de material ferroeléctrico sintonizable (BST) para el ajuste externo de los parámetros de medio efectivo. Por lo tanto se diseñan unos varactores BST que son colocados entre los elementos metálicos que conforman la FSS. El efecto de la superficie selectiva en frecuencia es estudiado en dos antenas diferentes – antena ELPOSD (End-Loaded Planar Open-Sleeve Dipole) y una antena de parche microstrip. La antena ELPOSD consiste en un dipolo plano convencional con dos elementos parásitos muy juntos, y una carga en cada extremo del dipolo. Los beneficios principales de este tipo de antenas es que, además del rendimiento similar de la antena POSD (Planar Open-Sleeve Dipole) convencional, las antenas ELPOSD pueden ser miniaturizadas. La antena parche utilizada en este trabajo es un elemento metálico cuadrado plano alimentado a través de una línea microstrip. El material ferroeléctrico Barium Strontium Titanate (BST) es un material muy bien conocido hasta el momento. Para diseñar los varactores se utiliza una película delgada de BST, junto con los capacitores interdigitales (IDCs) que se utilizan en la capa del metal. La antena general consiste en un sustrato de múltiples capas donde en una capa se encuentra la Superficie selectiva en frecuencia (FSS) sintonizable y en otra la antena dipolo o antena de parche. La capacidad de la FSS completa varía introduciendo el material ferroeléctrico BST en el varactor. Como puede verse en los resultados, variando la permitividad del material BST de 200 a 300 se consigue una variación en frecuencia de 4.15 GHz a 3.5 GHz con una distancia alrededor de 100 MHz entre frecuencias resonantes. Esto equivale a una variación de la frecuencia alrededor del 8% entre los valores de permitividad adyacentes.A “metamaterial” by its widely accepted definition is an artificially engineered structure that gains its material properties from its structure as opposed to its intrinsic material composition. The field of metamaterials has gained much attention within the scientific community over the past decade. With continuing advances and discoveries leading the way to practical applications, metamaterials have earned the attention of technology-based corporations and defense agencies interested in their use for next generation devices. Frequency Selective Surfaces (FSS) are a potent variety of metamaterials that, depending on the surface geometry, can be used to engineer specific radiation properties such as directional emission, linear and circular polarized emission, and spectral selectivity. The elements of the FSS can either be patches or apertures, and in traditional designs, the FSS usually operates around the half-wavelength resonance of the elements. In this project a Frequency Selective Surface (FSS) is used in order to realize tunable metamaterials –a broad class of controllable artificially engineered metamaterials, and develop a tunable antenna operating at 2.4 GHz. The FSS consist of an array of square patches loaded with varactors and tunable ferroelectric thin film capacitors (BST) for external tuning of the effective medium parameters. Therefore a BST varactor is designed and located between the patches of the FSS. The effect of the Frequency Selective Surface is studied in two different antennas –an End-Loaded Planar Open-Sleeve Dipole (ELPOSD) and a Square Patch. An End-Loaded Planar Open-Sleeve Dipole consist of a conventional planar dipole with two closely spaced parasitic elements, or sleeves, and loaded stubs at the end of the dipole. The main benefits of this type of antennas is that in addition to retaining similar performance to that of conventional planar open-sleeve dipole, end-loaded planar opensleeve dipole (ELPOSD) antennas can be miniaturized. The Square Patch antenna used in this work is a conventional planar square patch feed with a microstrip line. Barium Strontium Titanate (BST) is a well-known ferroelectric material and up to now. A BST thin film is used to design the varactors, along with the Interdigital Capacitors (IDCs) geometry used in the metal layer. The overall antenna consists of a multilayer substrate with tunable FSS layer and dipole or patch antenna. The capacitance of the whole FSS changes introducing the BST ferroelectric material into the varactor. As can be seen in the results, by varying the BST permittivity from 200 to 300, a variation in frequency is achieved from 1.98 GHz to 1.717 GHz with a distance around 100 MHz between resonance frequencies, which equals a variation of the frequency about 8% in the adjacent permittivity values.Ingeniería de TelecomunicaciónTelekomunikazio Ingeniaritz

Engineering evaluations and studies. Volume 3: Exhibit C

High rate multiplexes asymmetry and jitter, data-dependent amplitude variations, and transition density are discussed

Design of MIMO Antenna for a Realistic Mobile Phone Platform Using Characteristic Modes

The Theory of Characteristic Modes (TCM) provides an alternative means of antenna synthesis in compact mobile handsets by taking into account the chassis. This makes it possible to create dual-element Multiple-Input Multiple-Output (MIMO) antennas in mobile handsets with very little coupling and correlation between the two antennas. But apart from the antennas, modern mobile phones are each equipped with internal components such as a touch screen, a battery, a camera and a microphone that are capable of affecting the characteristic mode behavior of the chassis. Until now, very little work has been done to study the impact of these internal components on MIMO antenna design using TCM. In this thesis, adetailed evaluation was performed on the effects that the internal components of a mobile phone have on the characteristic modes of the antenna chassis and how these effects can be mitigated. In particular, we compared the individual eigenmodes obtained in a plain chassis structure with their corresponding (or equivalent) modes obtained after addition of the components (individually and as complete unit) and quantify the correlation between the corresponding modes. The results show that, at frequencies lower than 1 GHz, the fundamental mode of the plain chassis structure is largely unaffected by the introduction of the internal components. On the other hand, the two modes attributed to the two T-strips on the plain chassis experienced a shift in their resonant frequencies when the internal components were introduced. However, it was found that their original resonant frequencies could be restored using minor structural changes. At higher frequencies, the introduction of the components was found to have very little impact on the characteristic modes. Finally, the chassis with all the components was employed to design a dual-band T-strip antenna, which relied on the restoration of the modal resonant frequencies to provide a broadband resonance at below 1 GHz, highlighting the usefulness of TCM analysis in antenna design

Engineering evaluations and studies. Volume 2: Exhibit B, part 1

Ku-band communication system analysis, S-band system investigations, payload communication investigations, shuttle/TDRSS and GSTDN compatibility analysis are discussed

High-performance wireless interface for implant-to-air communications

Nous élaborons une interface cerveau-machine (ICM) entièrement sans fil afin de fournir un système de liaison directe entre le cerveau et les périphériques externes, permettant l’enregistrement et la stimulation du cerveau pour une utilisation permanente. Au cours de cette thèse, nous explorons la modélisation de canal, les antennes implantées et portables en tant que propagateurs appropriés pour cette application, la conception du nouveau système d’un émetteur-récepteur UWB implantable, la conception niveau système du circuit et sa mise en oeuvre par un procédé CMOS TSMC 0.18 um. En plus, en collaboration avec Université McGill, nous avons conçu un réseau de seize antennes pour une détection du cancer du sein à l’aide d’hyperfréquences. Notre première contribution calcule la caractérisation de canal de liaison sans fil UWB d’implant à l’air, l’absorption spécifique moyennée (ASAR), et les lignes directrices de la FCC sur la densité spectrale de puissance UWB transmis. La connaissance du comportement du canal est nécessaire pour déterminer la puissance maximale permise à 1) respecter les lignes directrices ANSI pour éviter des dommages aux tissus et 2) respecter les lignes directrices de la FCC sur les transmissions non autorisées. Nous avons recours à un modèle réaliste du canal biologique afin de concevoir les antennes pour l’émetteur implanté et le récepteur externe. Le placement des antennes est examiné avec deux scénarios contrastés ayant des contraintés de puissance. La performance du système au sein des tissus biologiques est examinée par l’intermédiaire des simulations et des expériences. Notre deuxième contribution est dédiée à la conception des antennes simples et à double polarisation pour les systèmes d’enregistrement neural sans fil à bande ultra-large en utilisant un modèle multicouches inhomogène de la tête humaine. Les antennes fabriquées à partir de matériaux flexibles sont plus facilement adaptées à l’implantation ; nous étudions des matériaux à la fois flexibles et rigides et examinons des compromis de performance. Les antennes proposées sont conçues pour fonctionner dans une plage de fréquence de 2-11 GHz (ayant S11-dessous de -10 dB) couvrant à la fois la bande 2.45 GHz (ISM) et la bande UWB 3.1-10.6 GHz. Des mesures confirment les résultats de simulation et montrent que les antennes flexibles ont peu de dégradation des performances en raison des effets de flexion (en termes de correspondance d’impédance). Finalement, une comparaison est réalisée entre quatre antennes implantables, couvrant la gamme 2-11 GHz : 1) une rigide, à la polarisation simple, 2) une rigide, à double polarisation, 3) une flexible, à simple polarisation et 4) une flexible, à double polarisation. Dans tous les cas une antenne rigide est utilisée à l’extérieur du corps, avec une polarisation appropriée. Plusieurs avantages ont été confirmés pour les antennes à la polarisation double : 1) une taille plus petite, 2) la sensibilité plus faible aux désalignements angulaires, et 3) une plus grande fidélité. Notre troisième contribution fournit la conception niveau système de l’architecture de communication sans fil pour les systèmes implantés qui stimulent simultanément les neurones et enregistrent les réponses de neurones. Cette architecture prend en charge un grand nombre d’électrodes (> 500), fournissant 100 Mb/s pour des signaux de stimulation de liaison descendante, et Gb/s pour les enregistrements de neurones de liaison montante. Nous proposons une architecture d’émetteur-récepteur qui partage une antenne ultra large bande, un émetteur-récepteur simplifié, travaillant en duplex intégral sur les deux bandes, et un nouveau formeur d’impulsions pour la liaison montante du Gb/s soutenant plusieurs formats de modulation. Nous présentons une démonstration expérimentale d’ex vivo de l’architecture en utilisant des composants discrets pour la réalisation les taux Gb/s en liaison montante. Une bonne performance de taux d’erreur de bit sur un canal biologique à 0,5, 1 et 2 Gb/s des débits de données pour la télémétrie de liaison montante (UWB) et 100 Mb/s pour la télémétrie en liaison descendante (bande 2.45 GHz) est atteinte. Notre quatrième contribution présente la conception au niveau du circuit d’un dispositif d’émission en duplex total qui est présentée dans notre troisième contribution. Ce dispositif d’émission en duplex total soutient les applications d’interfaçage neural multimodal et en haute densité (les canaux de stimulant et d’enregistrement) avec des débits de données asymétriques. L’émetteur (TX) et le récepteur (RX) partagent une seule antenne pour réduire la taille de l’implant. Le TX utilise impulse radio ultra-wide band (IR-UWB) basé sur une approche alliant des bords, et le RX utilise un nouveau 2.4 GHz récepteur on-off keying (OOK).Une bonne isolation (> 20 dB) entre le trajet TX et RX est mis en oeuvre 1) par mise en forme des impulsions transmises pour tomber dans le spectre UWB non réglementé (3.1-7 GHz), et 2) par un filtrage espace-efficace du spectre de liaison descendante OOK dans un amplificateur à faible bruit RX. L’émetteur UWB 3.1-7 GHz peut utiliser soit OOK soit la modulation numérique binaire à déplacement de phase (BPSK). Le FDT proposé offre une double bande avec un taux de données de liaison montante de 500 Mbps TX et un taux de données de liaison descendante de 100 Mb/s RX, et il est entièrement en conformité avec les standards TSMC 0.18 um CMOS dans un volume total de 0,8 mm2. Ainsi, la mesure de consommation d’énergie totale en mode full duplex est de 10,4 mW (5 mW à 100 Mb/s pour RX, et de 5,4 mW à 500 Mb/s ou 10,8 PJ / bits pour TX). Notre cinquième contribution est une collaboration avec l’Université McGill dans laquelle nous concevons des antennes simples et à double polarisation pour les systèmes de détection du cancer du sein à l’aide d’hyperfréquences sans fil en utilisant un modèle multi-couche et inhomogène du sein humain. Les antennes fabriquées à partir de matériaux flexibles sont plus facilement adaptées à des applications portables. Les antennes flexibles miniaturisées monopôles et spirales sur un 50 um Kapton polyimide sont conçus, en utilisant high frequency structure simulator (HFSS), à être en contact avec des tissus biologiques du sein. Les antennes proposées sont conçues pour fonctionner dans une gamme de fréquences de 2 à 4 GHz. Les mesures montrent que les antennes flexibles ont une bonne adaptation d’impédance dans les différentes positions sur le sein. De Plus, deux antennes à bande ultralarge flexibles 4 × 4 (simple et à double polarisation), dans un format similaire à celui d’un soutien-gorge, ont été développés pour un système de détection du cancer du sein basé sur le radar.We are working on a fully wireless brain-machine-interface to provide a communication link between the brain and external devices, enabling recording and stimulating the brain for permanent usage. In this thesis we explore channel modeling, implanted and wearable antennas as suitable propagators for this application, system level design of an implantable UWB transceiver, and circuit level design and implementing it by TSMC 0.18 um CMOS process. Also, in a collaboration project with McGill University, we designed a flexible sixteen antenna array for microwave breast cancer detection. Our first contribution calculates channel characteristics of implant-to-air UWB wireless link, average specific absorption rate (ASAR), and FCC guidelines on transmitted UWB power spectral density. Knowledge of channel behavior is required to determine the maximum allowable power to 1) respect ANSI guidelines for avoiding tissue damage and 2) respect FCC guidelines on unlicensed transmissions. We utilize a realistic model of the biological channel to inform the design of antennas for the implanted transmitter and the external receiver. Antennas placement is examined under two scenarios having contrasting power constraints. Performance of the system within the biological tissues is examined via simulations and experiments. Our second contribution deals with designing single and dual-polarization antennas for wireless ultra-wideband neural recording systems using an inhomogeneous multi-layer model of the human head. Antennas made from flexible materials are more easily adapted to implantation; we investigate both flexible and rigid materials and examine performance trade-offs. The proposed antennas are designed to operate in a frequency range of 2–11 GHz (having S11 below -10 dB) covering both the 2.45 GHz (ISM) band and the 3.1–10.6 GHz UWB band. Measurements confirm simulation results showing flexible antennas have little performance degradation due to bending effects (in terms of impedance matching). Finally, a comparison is made of four implantable antennas covering the 2-11 GHz range: 1) rigid, single polarization, 2) rigid, dual polarization, 3) flexible, single polarization and 4) flexible, dual polarization. In all cases a rigid antenna is used outside the body, with an appropriate polarization. Several advantages were confirmed for dual polarization antennas: 1) smaller size, 2) lower sensitivity to angular misalignments, and 3) higher fidelity. Our third contribution provides system level design of wireless communication architecture for implanted systems that simultaneously stimulate neurons and record neural responses. This architecture supports large numbers of electrodes (> 500), providing 100 Mb/s for the downlink of stimulation signals, and Gb/s for the uplink neural recordings. We propose a transceiver architecture that shares one ultra-wideband antenna, a streamlined transceiver working at full-duplex on both bands, and a novel pulse shaper for the Gb/s uplink supporting several modulation formats. We present an ex-vivo experimental demonstration of the architecture using discrete components achieving Gb/s uplink rates. Good bit error rate performance over a biological channel at 0.5, 1, and 2 Gbps data rates for uplink telemetry (UWB) and 100 Mbps for downlink telemetry (2.45 GHz band) is achieved. Our fourth contribution presents circuit level design of the novel full-duplex transceiver (FDT) which is presented in our third contribution. This full-duplex transceiver supports high-density and multimodal neural interfacing applications (high-channel count stimulating and recording) with asymmetric data rates. The transmitter (TX) and receiver (RX) share a single antenna to reduce implant size. The TX uses impulse radio ultra-wide band (IR-UWB) based on an edge combining approach, and the RX uses a novel 2.4-GHz on-off keying (OOK) receiver. Proper isolation (> 20 dB) between the TX and RX path is implemented 1) by shaping the transmitted pulses to fall within the unregulated UWB spectrum (3.1-7 GHz), and 2) by spaceefficient filtering (avoiding a circulator or diplexer) of the downlink OOK spectrum in the RX low-noise amplifier. The UWB 3.1-7 GHz transmitter can use either OOK or binary phase shift keying (BPSK) modulation schemes. The proposed FDT provides dual band 500-Mbps TX uplink data rate and 100 Mbps RX downlink data rate, and it is fully integrated into standard TSMC 0.18 um CMOS within a total size of 0.8 mm2. The total measured power consumption is 10.4 mW in full duplex mode (5 mW at 100 Mbps for RX, and 5.4 mW at 500 Mbps or 10.8 pJ/bit for TX). Our fifth contribution is a collaboration project with McGill University which we design single and dual-polarization antennas for wireless ultra-wideband breast cancer detection systems using an inhomogeneous multi-layer model of the human breast. Antennas made from flexible materials are more easily adapted to wearable applications. Miniaturized flexible monopole and spiral antennas on a 50 um Kapton polyimide are designed, using a high frequency structure simulator (HFSS), to be in contact with biological breast tissues. The proposed antennas are designed to operate in a frequency range of 2–4 GHz (with reflection coefficient (S11) below -10 dB). Measurements show that the flexible antennas have good impedance matching while in different positions with different curvature around the breast. Furthermore, two flexible conformal 4×4 ultra-wideband antenna arrays (single and dual polarization), in a format similar to that of a bra, were developed for a radar-based breast cancer detection system

DEVELOPING ELECTROMAGNETIC AND PHOTONIC DEVICES BY USING ARTIFICIAL DIELECTRIC MATERIALS

Transformation-Optics (TO) is a new theoretical tool that allows for designing advanced electromagnetic and photonic devices. TO theory often prescribes material parameters for transformed media that cannot be found in nature. Metamaterials (MMs) were initially used for realization of TO-based devices. However, conventional MMs possess noticeable losses caused by their metallic parts that prevents their utilization in optical range. Alternatively, photonic crystals (PhCs) formed from arrays of low-loss all-dielectric elements can be good substitutes for building TO-prescribed devices. Metasurfaces (MSs) comprised from 2D arrays of dielectric resonators (DRs) have been found as other promising candidates for realizing flat and efficient devices. In our work, we explored incorporation of all-dielectric artificial media in invisibility cloaks, representing the most exciting TO application, wave collimators, and MSs. We studied associated electromagnetic and photonic phenomena and solved engineering problems met at the development of device prototypes. We designed and used anisotropic PhCs composed of rectangular lattice dielectric rod arrays to build up a cylindrical cloak medium realizing prescriptions of TO (Chapter 2). We also formed another cylindrical invisibility cloak by utilizing the self-collimation phenomenon in PhCs without considering TO prescriptions for turning the wave in the cloak medium (Chapter 3). Furthermore, we designed a wave collimator by employing high-anisotropic rectangular lattice dielectric rod arrays with unidirectional near-zero refractive indices (Chapter 4). Then, we studied the resonance and scattering responses of MSs composed of dielectric disks, while altering the periodicity of MSs. Our results demonstrated that periodicity of arrays has significant influence on defining the responses of MSs. (Chapter 5). Increasing lattice constants of dielectric MSs provided us with an opportunity to investigate interactions between lattice resonances (LRs) and dipolar electric and magnetic resonances that affected characteristics of MSs (Chapter 6). We analyzed the formation of Fano responses and wave interference processes in dense MSs to reveal the nature of electromagnetically induced transparency (EIT) that was detected at the frequency of electric dipolar resonance. (Chapter 7)

Metamaterial

In-depth analysis of the theory, properties and description of the most potential technological applications of metamaterials for the realization of novel devices such as subwavelength lenses, invisibility cloaks, dipole and reflector antennas, high frequency telecommunications, new designs of bandpass filters, absorbers and concentrators of EM waves etc. In order to create a new devices it is necessary to know the main electrodynamical characteristics of metamaterial structures on the basis of which the device is supposed to be created. The electromagnetic wave scattering surfaces built with metamaterials are primarily based on the ability of metamaterials to control the surrounded electromagnetic fields by varying their permeability and permittivity characteristics. The book covers some solutions for microwave wavelength scales as well as exploitation of nanoscale EM wavelength such as visible specter using recent advances of nanotechnology, for instance in the field of nanowires, nanopolymers, carbon nanotubes and graphene. Metamaterial is suitable for scholars from extremely large scientific domain and therefore given to engineers, scientists, graduates and other interested professionals from photonics to nanoscience and from material science to antenna engineering as a comprehensive reference on this artificial materials of tomorrow

EMPLOYING DIELECTRIC-BASED MEDIA FOR CONTROLLING FIELD PATTERNS AND WAVE PROPAGATION IN ADVANCED ELECTROMAGNETIC DEVICES

Rapid progress in developing electromagnetic devices and in governing the wave propagation during last years caused renewed interest to dielectric materials. First, engineered dielectric structures with spatial dispersion of their parameters came to replace uniform substrates in antennas and other resonance devices. Then additional boom of dielectric applications was caused by the possibility to employ dielectrics as materials of artificial media. Later, attention of researchers was attracted to properties of the media composed of dielectric resonators (DRs). Currently DRs are used to create metamaterials – the media with unprecedented properties, which cannot be found in nature. Dielectric photonic crystals and metamaterials are considered as the most perspective materials for photonics, since they can be integrated in devices without loss problems, which characterize, for example, plasmonic techniques. Recently, a booming interest emerged to employing in photonics directional light scattering from dielectric particles, since the wavelengths of this light could be controlled by dimensions of particles and their dielectric permittivity. Our work followed basic innovations, which defined contemporary employment of dielectrics in electromagnetics and photonics. In particular, we started from working out new engineering approaches to developing dielectric substrates in patch structures inspired by microstrip patch antennas, which are proposed to serve as MRI RF probes (Chapter 2). Then we redirected our attention to the problems, which restricted employment of dielectrics in left-handed media. In particular, we have shown that negative refraction in all-dielectric metamaterials is irrelevant to Mie resonances in dielectric elements (Chapter 3). Next, we turned to analysis of problems defining directional scattering from dielectric metasurfaces and have demonstrated that the nature of observed phenomena cannot be correctly understood without accounting for strong interaction between “atoms” of metasurafces (Chapter 4). Finally we discussed selected problems met at implementation of photonic crystals in the media of transformation optics based devices and have shown that some of the problems can be solved at employing the phenomenon of self-collimation, characteristic for periodic photonic structures (Chapter 5)