Reconfigurable Reflectarrays and Array Lenses for Dynamic Antenna Beam Control: A Review

Advances in reflectarrays and array lenses with electronic beam-forming capabilities are enabling a host of new possibilities for these high-performance, low-cost antenna architectures. This paper reviews enabling technologies and topologies of reconfigurable reflectarray and array lens designs, and surveys a range of experimental implementations and achievements that have been made in this area in recent years. The paper describes the fundamental design approaches employed in realizing reconfigurable designs, and explores advanced capabilities of these nascent architectures, such as multi-band operation, polarization manipulation, frequency agility, and amplification. Finally, the paper concludes by discussing future challenges and possibilities for these antennas.Comment: 16 pages, 12 figure

Electrically tuned microwave devices using liquid crystal technology

An overview of liquid crystal technology for microwave and millimeter-wave frequencies is presented. The potential of liquid crystals as reconfigurable materials arises from their ability for continuous tuning with low power consumption, transparency, and possible integration with printed and flexible circuit technologies. This paper describes physical theory and fundamental electrical properties arising from the anisotropy of liquid crystals and overviews selected realized liquid crystal devices, throughout four main categories: resonators and filters, phase shifters and delay lines, antennas, and, finally, frequency-selective surfaces and metamaterials.Pouria Yaghmaee, Onur Hamza Karabey, Bevan Bates, Christophe Fumeaux and Rolf Jakob

Miniature Antenna with Frequency Agility

International audienc

Digital Microfluidics as a Reconfiguration Mechanism for Antennas

This dissertation work concentrates on novel reconfiguration technologies, including design, microfabrication, and characterization aspects with an emphasis on their applications to multifunctional reconfigurable antennas. In the literature, reconfigurable antennas have made use of various reconfiguration techniques. The most common techniques utilized revolved around switching mechanisms. Other techniques such as the incorporation of variable capacitors, varactors, and physical structure manipulation surfaced recently to overcome many problems faced in using switches and their biasing. Usage of fluids (micro-fluidic or otherwise) in antennas provides a conceptually easy reconfiguration mechanism in the aspect of physical alteration. However, a requirement of pumps, valves, etc. for liquid transportation makes the antenna implementations rather impractical for the real-life scenarios. This work reports on design and experiments conducted to evaluate the electrowetting on dielectric (EWOD) driven digital microfluidics as a reconfiguration mechanism for antennas

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

94 GHz Beam Scanning Dual-Reflector Antenna with a Sub-Reflectarray

A Cassegrain dual-reflector antenna which employs a flat reflectarray subreflector was analysed in a recent paper [1]. It was shown that the antenna beam can be scanned by introducing an appropriate progressive phase distribution across the reflectarray surface. This configuration is very attractive for steerable beam applications, because it combines the high gain and broad bandwidth properties of the parabolic main reflector with the simplicity of manufacturing a small electronically reconfigurable microstrip reflectarray antenna. The subreflector could be constructed on a thin liquid crystal (LC) substrate, and control of the phase distribution across the aperture would be achieved by applying a bias voltage to the individual elements in the patch array [2, 3]. In addition to the simplicity of this biasing arrangement, phase shifters based on LC materials can be designed to operate with no upper limit on the operating frequency range, thereby removing the main disadvantage of many existing active control technologies. Moreover precision micromachining processes and a quasi–optical measurement technique which are suitable for manufacturing and characterising sub mm wavelength phase agile reflectarrays, have recently been demonstrated at frequencies up to 170 GHz [4]. In this paper we present the design of a dual-reflector antenna which could use an ‘active’ sub-reflectarray based on liquid crystals to produce the required Earth scene scan profile of a limbsounder radiometric instrument [5]. The validity of the beam scanning concept has been demonstrated by designing, manufacturing and measuring the radiation patterns of a 120mm diameter offset parabolic reflector at 94 GHz. In the first phase of the project we have used three planar solid metal subreflectors of diameter 28-mm to generate a focussed beam in the boresight direction, and at offset scan angles of 2.5° and 5°. Experimental results are shown to be in reasonably good agreement with numerical simulations. In the second phase of the work, the solid metal subreflectors are replaced by a passive microstrip patch subreflectarray which is designed to scan the beam to an angle of 5º. The final stage of the project will employ an electronically controllable LC reflectarray subreflector which will be used to scan the beam over the angular range 0 º to 5º

ELECTRONICAL LY RECONFIGURABLE FS S - INSPIRED TRANSMITARRAY FOR TWO DIMENS IONAL BEAMSTEERING FOR 5G ANDRADAR APPL ICATIONS AT 2 8 GHZ

In this dissertation, the author’s work on a 28 GHz transmitarray capable of antenna beamsteering for various wireless applications, is presented. Such device allows for the adjustment of the radiation pattern of an antenna by changing its main lobe direction, without the need of any mechanical means. A unit-cell based on a square-slot Frequency Selective Surface (FSS) is designed, simulated and optimised through several full-wave simulations, using an electromagnetic solver (CST MWS). Subsequently, the unit-cell was extended to a 10x10 array configuration in order to enable Two-dimensional (2D) beamsteering. This work yielded the fabrication of a prototype composed of four passive transmitarray lens, which were experimentally tested and characterised. Finally, a novel unit-cell based on a double square-slot intended aiming at active beamsteering was also studied and optimised in simulation environment. From this work, it was demonstrated that transmitarray can be seen as feasible alternative to many traditional beamsteering techniques, such as phased antenna arrays, while reducing the RF burden of the overall system using only a single radiation source. This fact, allied with it’s ease of integration, reduced cost and low-profile characteristics make transmitarrays a desirable solution for 5G and RADAR applications, among others