Reflective array antenna

About: Reflective array antenna is a research topic. Over the lifetime, 4366 publications have been published within this topic receiving 57884 citations.

A Novel Integrated UWB–UHF One-Port Antenna for Localization and Energy Harvesting

Abstract: In this work, a novel, compact, single-port antenna combining both UWB and UHF bands is presented. This solution is proposed for next-generation passive RFID tags, performing communication and localization through UWB technology and efficient energy harvesting in the UHF band, but it is also designed to keep compatibility with previous tags generations. The UWB communication is deployed by means of an Archimedean spiral topology, while energy harvesting at UHF is obtained by suitably extending the spiral outer arms, thus realizing a meandered dipole, without affecting the UWB behavior. The single-port architecture provides an overall size reduction, while preserving the radiation performance in both the operating bands. This solution allows a direct connection to future integrated UWB–UHF chips, to standard RFID chips, or to a diplexer for suitably combining the UWB and the UHF functionalities. A prototype of this new antenna, realized on a standard FR-4 substrate, is first presented to validate the proposed novel design. As a second step, the same architecture is scaled on a paper substrate in view of its fully ecocompatible realization to be exploited by future pervasive RFID applications. The compact design of the antenna-feeding network in discrete technology is also presented.

A Novel Wide-Angle Scanning Phased Array Based on Dual-Mode Pattern-Reconfigurable Elements

Abstract: A novel linear phased array design for wide-angle scanning applications is presented in this letter. Eight pattern-reconfigurable antennas (PRAs), capable of switching their patterns from quasi-broadside to monopole-like radiation with the help of p-i-n diodes, are used as the basic elements. By combining the scans of the PRAs working at two symmetrical modes in two subspaces, the phased array is able to scan its beam from $-$ 81 $^{\circ }$ to +81 $^{\circ }$ in the E-plane with a gain fluctuation less than 3 dB. The proposed array is simulated, fabricated, and measured. The simulated and measured results show that the performance of the phased array is superior to that of the former designed arrays using PRAs due to its less reconfigurable modes, simpler biasing network, and wider beam-scanning coverage.

Self-installable switchable antenna

Abstract: A system, method, and apparatus for selecting a set of antennas, for use during operation of a radio system, from a plurality of antennas. The system, method and apparatus may include selecting one antenna that is part of an array of antennas. Then measuring characteristics of radio signals received at the antenna. The selection and measuring of characteristic is repeated for a desired number of antennas in the array. Then, the measurements are combined, and the combinations of antennas are ranked based upon the combined measurement. From the ranking combinations of antennas are selected for use during operation of a radio system.

A Kinetic Study of Glutamic-Aspartic Transaminase

Abstract: : Standard rectangular wave guides, loaded by the use of a ridge, were designed to make parallel slot antenna arrays capable of being scanned =45 degrees off the broadside position. The array design is proposed as a means of using the same aperture for multiple-frequency bands. Radiation patterns of 36-slot and 72-slot planar arrays are included. (Author)

Analysis of large antenna systems

Abstract: The research presented in this thesis has been conducted within the framework of the Square Kilometre Array (SKA) project. SKA is a next generation radio telescope that will have a receiver sensitivity two orders of magnitude larger than the most sensitive radio telescope currently in operation. To meet the specifications, various low-cost low-noise actively beamformed receiving array antennas are being considered. A major problem in designing these systems is that the present-day commercially available electromagnetic solvers need an excessive amount of memory and simulation time to solve electrically large antenna problems. Moreover, it is essential to be able to analyze the receiver sensitivity of large antenna array systems to understand the sensitivity limiting factors. No dedicated commercial software tools exist that can analyze the receiver sensitivity of entire antenna systems specifically for radio astronomy. The thesis subject deals with two major challenges: (i) To accurately compute the impedance and radiation characteristics of realistically large and complex antenna arrays using only moderate computing power, particularly, of single and dual-polarized arrays of 100+ Tapered Slot Antenna (TSA) elements that are electrically interconnected. If the collection of these elements forms a subarray of a larger system, it is also of interest to analyze an array of disjoint subarrays. (ii) To characterize the system sensitivity of actively beamformed arrays of strongly coupled antenna elements. To address the above challenges, a conventional method-of-moments approach to solving an electric-field integral equation is enhanced using the Characteristic Basis Function Method (CBFM) to handle electrically large antenna problems. The generation of the associated reduced matrix equation is expedited by combining the CBFM with the Adaptive Cross Approximation (ACA) technique. Furthermore, because an overlapping domain decom270 Bibliography position technique is employed, Characteristic Basis Functions (CBFs) are generated that partially overlap to ensure the continuity of the current between adjacent subdomains that are electrically interconnected. While generating the CBFs, edge-singular currents are avoided by a post-windowing technique. Finally, a meshing strategy is proposed to optimally exploit the quasi-Toeplitz symmetry of the reduced moment matrix. The numerical accuracy and efficiency has been determined for numerous cases, among which a dual-polarized interconnected TSA array of 112 elements that has been fabricated and subsequently validated by measurements. The receiver system has been modeled by both a numerical and a semi-analytical method. The models account for a nonuniform brightness temperature distribution of the sky, mismatch effects, noise that emanates from amplifiers inputs and re-enters the system coherently through the mutually coupled antennas (noise coupling), beamformer weights, etc. Results are shown for a practical setup and design rules are derived which demonstrate that minimum receiver noise can be reached by noise matching the low-noise amplifiers to the active antenna reflection coefficient, rather than the passive one. Finally, it is demonstrated that the radiation efficiency of antennas is an important quantity that can degrade the system sensitivity severely. Nevertheless, a number of commercial software tools have shown to be inadequate as the computed efficiency exceeds 100%. A method is proposed which is numerically efficient and robust since it guarantees an efficiency below 100%.