Numerical analysis of the annular-ring loaded circular-disk microstrip antenna

The annular-ring-loaded (ARL) circular-disk microstrip antenna with thick substrate and mutual coupling problem is analyzed using the stratified medium Green's function and the spectral-domain formulation. The intent of the ARL microstrip antenna is to broaden the bandwidth of the antenna. Good agreement has been found between the numerical results and measured data in both resonance and input impedance analysis, even for an antenna with substrate thickness up to 0.1 wavelength. An ARL-disk antenna that had a thickness of 0.089 substrate wavelength and a relative bandwidth as high as 20% was designed. The radiation patterns in the E and H planes were very good, and the cross polarization was less than -6 dB.<>