The design optimization of miniature low profile antennas placed in close proximity to high-impedance surfaces

Abstract

The objective of the paper is to illustrate a new design optimization procedure for miniaturized antennas placed near a high-impedance surface, i.e., a perfect magnetic conductor (PMC). It is demonstrated that antennas can be optimized via a genetic algorithm (GA) to achieve superior performance characteristics (e.g., input impedance, VSWR, and gain) when placed in close proximity to a PMC ground plane as opposed to a standard perfect electric conductor (PEC) ground plane. A methodology that allows for the compensation of the coupling effects is introduced; it is based on optimizing the shape of a miniaturized fractal or stochastic antenna placed next to a PMC surface. It is also demonstrated that these genetically optimized antennas exhibit superior performance when compared to conventional half-wave dipoles with the same design specifications. Several case studies are presented that compare the performance of specific antennas when operating near PMC and PEC ground planes. It is shown that, in the case of a PMC ground plane, the desired VSWR specifications can be achieved by optimizing the geometries of fractal or stochastic antennas. This technique can be used to design miniature low-profile antennas successfully. We also illustrate the fact that it is not possible to achieve similar results using a conventional PEC ground plane.