Size Reduction Techniques for Microstrip Antennas

Dr. Jayanti Venkataraman

Department of Electrical Engineering, Rochester Institute of Technology

Abstract

As the trend towards miniaturization of electronic circuitry continues, antennas remain as the bulkiest part of wireless devices. The microstrip patch antenna is widely used in such applications because of its low-profile, simplicity of feed and compatibility with planar microstrip circuitry. The tradeoffs that exist between gain, radiation pattern, bandwidth, and physical size make antenna design a lengthy and tedious process. This presentation will illustrate some size reduction techniques for microstrip patch antennas.

Size reduction up to fifty percent for microstrip antennas has been achieved by placing Complimentary Split Ring Resonators (CSRR) in the ground plane creating a "left-handed" effect that results in a negative permittivity. Rectangular microstrip patch antennas have been constructed and validated through measurement. It has been observed that the best designs are for cases where CSRRs' "stop band" corresponds to the resonant frequency of the antenna. Another method for size reduction is by removing predefined slot shapes from the metal. A genetic algorithm is used to optimize the size and location of the slots on the patch. Size reduction of 75% has been achieved for a 6 GHz antenna. The work has been performed by interfacing the genetic algorithm to Ansoft High Frequency System Simulator (HFSS). One of the popular methods to enhance bandwidth and reduce the size of a microstrip patch is loading multiple slots along its edges. A particle swarm algorithm interfaced to HFSS has been utilized to optimize the dimensions of the slots to achieve size reduction and enhanced bandwidth. Results have yielded a doubling of the bandwidth and a 70% size reduction for a 2.4 GHz antenna. For a similar antenna configuration, a dual frequency antenna has been optimized that resonates at 1.9GHz and 2.4GHz.. A reconfigurable dual frequency microstrip patch antenna is created by reconfiguring its size using two rectangular patches that are connected together via RF MEMS switches designed for 8 GHz and 10 GHz. The RF MEMS switches are modeled using Ansoft's High Frequency Structure Simulator (HFSS). A reconfigurable double stub tuner using RF MEMS switches has been designed to match the antennas at each frequency. Validation of the design has been done using HFSS.

Biography

Dr. Jayanti Venkataraman is a Professor in the Electrical Engineering Department at the Rochester Institute of Technology (RIT) in Rochester, NY, USA. She is the Director of the Electromagnetics Theory and Applications (ETA) Laboratory in the Electrical Engineering Department at RIT where she has developed the area of Electromagnetics for the EE undergraduate and graduate programs. Her research interests are in theoretical modeling of microstrip antennas and integrated microwave circuits, composite right/left handed materials and applications, Numerical Optimization techniques, and Bioelectromagnetics. She also serves as a consultant to some RF and biomedical companies in Rochester. She is the 2001-02 recipient of the Eisenhart Award for Outstanding Teaching from the Rochester Institute of Technology and the 2007 IEEE Region 1 award for establishing a unique educational experience in the area of Electromagnetics, Microwaves and Antennas.