Effects of superstrates on the resonant frequency of rectangular microstrip antennas

This article presents the extended expression to calculate the environmental effect oil resonant frequency of multilayer rectangular microstrip antennas. The expression has been investigated for affective dielectric constant epsilon(eff) and resonant frequency f(r.) The effective dielectric constant epsilon(eff) of present Method has been compared with full wave numerical technique with and without loading. These are in good agreement within 1% accuracy. It has been observed that % change in f(r) due to cover and substrate thickness is around 3.2% and 20%, respectively, as their thickness is varying 19 times of its initial value. This variation is drastic for h(3)/h(2) = 0. 01. The maximum % variation in f(r) for one substrate and two superstrate is around 5% as h(4) varies front I nun to 5 nun. In case of unwanted air (h(3)), the % variation in f(r) of present method in comparison to experimental value is less than 1.0% for small air-gap and 0.4% for large air-gap for various spaced dielectric (E,), which reveals that the effect of superstrate in f(r) is small than substrate above the ground plane. The resonant frequency in suspended substrate microstrip antenna with and without superstrate is 21.8% and 28.15%, respectively, as h(1)/h(2) varies from 0.065 to 1.94. The resonant frequency of all the possible configuration is in good agreement with the experimental results. (C) 2007 Wiley Periodicals, Inc.