Circular ring microstrip antenna elements

The frequency characteristics of circular ring microstrip antennas were obtained as a function of relative aperture radius. In all cases the resonant frequency was normalized to that of an ideal disk microstrip antenna with the same radius, and assumed magne tic wall boundary conditions. Since, at this time, an exact value for the complex wall admittance is not known, an equivalent admittance was derived for each of several commonly used models. This admittance was then used as the boundary condition for the computation of the resonant frequency as a function of relative aperture radius. Results of these calculations are shown; also shown is the comparison with experiment.