Designs of regular shape microstrip antennas backed by bow-tie shape ground plane for enhanced antenna characteristics

Abstract

Designs of microstrip antenna backed by defected ground plane structure have been extensively reported for reducing the cross-polar radiation level. However, reported configurations do not show any improvement in antenna bandwidth and gain. In this paper, novel designs of rectangular, circular, and equilateral triangular microstrip antennas backed by bow-tie shape ground plane are proposed on thinner FR4 substrate, in 1500 MHz frequency range. In addition to the cross-polar level reduction, each of the proposed designs offers a reduction in the resonance frequency (patch size), and an increase in the bandwidth and gain. The design using rectangular patch offers 10 dB reduction in the cross-polar levels with 4.7% reduction in the frequency whereas using the circular patch, reduction in the frequency by 8.5%, cross-polar level reduction by 41 dB, improvement in the bandwidth and gain by three times and 0.7 dBi, respectively, is obtained. An equilateral triangular patch offers optimum performance. Here in addition to the frequency and cross-polar level reduction by more than 10% and 20 dB, respectively, bandwidth improvement by more than five times and gain by 1.3 dBi are achieved. All these results are obtained on thinner and lossy FR4 substrate, thus they are notable. The measurements have been carried out for the result validation and a closer match with the simulated results, is obtained.