Theoretical and experimental study of an annular ring patch antenna on two layers

In this article, a set of closed form expressions is presented to predict the resonant frequency, quality factors, impedance-bandwidth and gain of an annular ring patch antenna on two layers fed by a coaxial probe. This model is very simple and fast and directly applied to the computer aided design (CAD). The expressions for equivalent relative permittivity and input impedance are derived. Unlike the previous models, very simple expressions for computation of the quality factors, input resistance at resonance, directivity and gain have been proposed. The present work is developed using the cavity model and single resonant parallel R-L-C circuit along with probe reactance. The computed values using the present model are in good agreement with the simulation and experimental findings for wider range of variation of inner to outer radii ratio of the ring, substrate electrical parameters, probe location and air gap.