Bandwidth widening in an annular ring microstrip antennas with superstrate

A theoretical and numerical analysis of an annular ring microstrip antennas with superstrate is performed in order to obtain a wider bandwidth operation. At the same time the complex resonant frequency of the structure is determined. The study is performed by using a full wave analysis and Galerkin´s moment method in Hankel transform domain by taking surface wave contributions into account. The possibility of achieving larger bandwidth operation with TM/sub 11/ mode which originally shows narrow bandwidth characteristics in single layer annular ring antenna is investigated. Numerical results for different antenna parameters are given. The results indicate that the resonant frequency decreases with increasing superstrate thickness and the bandwidth increases for increasing superstrate dielectric constant values.