Analysis of aperture-coupled microstrip antenna and array with an airgap

The tunable characteristic of an aperture-coupled microstrip antenna with an airgap between the substrate and the ground plane is investigated. Numerical results on input impedance, SWR bandwidth, resonant frequency and far-field radiation patterns are given. Computed results of input SWR against frequency are compared with experimental data. The scan characteristics of an infinite array of aperture-coupled microstrip antennas with an airgap are also studied using a full-wave analysis. The periodic spectral Green's functions are derived by the Floquet theorem. The calculated reflection coefficients versus scan angle in an arbitrary scan plane and against frequency when scanning at the broadside direction are presented.