Computation of resonant frequency of annular-ring-loaded circular patch using cavity model analysis

In this paper, the annular-ring-loaded (ARL) circular patch is revisited. By applying suitable boundary conditions at the interfaces, the problem is solved. The structure is considered as a disk with a ring slot etched in-between. The narrow slot divides the entire region into two parts. The slot is modeled as a π-type admittance network. Using circuit theory, the modal-current discontinuity is deduced and a transcendental relation giving the resonant frequency for nth mode is obtained. It is shown that the dominant-mode resonant frequency depends on where the probe is located inside the circle or the annular ring. The theoretical predictions are compared with the results obtained using IE3D, a commercial method of moments (MoM)-based solver. Comparison is also made with the published results as well as the experimental results and agreement of better than 2% to 3% is obtained. The analytical tool presented is simple in approach and computationally fast.