Radiation characterstics of annular microstrip antenna

A considerable amount of work has been done in recent years on the resonant behavior and the radiation characteristics of annular microstrip structures. The radiation fields have been evaluated by utilizing a host of techniques ranging from the use of a simple cavity model to the use of the spectral domain technique in Fourier-Hankel transform domain and the use of the method of matched asymptotic expansion. In this paper, known closed form expressions for radiation fields based on the cavity model are used to derive the expressions for radiation resistance, directivity, bandwidth and other characteristics of annular microstrip antennas. The results conform to similar results for other microstrip antennas. A simple method to calculate radiation characteristics such as radiation resistance, directivity, and bandwidth together with some typical results for annular micros trip antennas has been considered. The results should be helpful in design of such antennas.