Effect of a Cylindrical Cavity on the Resonance of a Circular Microstrip Patch With Variable Air-Gap

The effect of a cylindrical cavity enclosure in shifting the resonant frequency of a suspended substrate circular microstrip patch with variable air-gap is investigated and an analytical formulation is proposed to accurately estimate the same. A new factor indicating the proximity effect of the cavity wall is also suggested and studied. The proposed formula is compared with some measurements and simulated data generated using Ansoft's HFSS v9.2 revealing much closer agreement compared to a previously reported formulation.