Analysis of the four basic resonant mode types of an enclosed rectangular microstrip patch including the effects of coupling between patches

The lowest-order resonant mode of each of the four resonant mode types of an enclosed rectangular microstrip patch on a dielectric substrate is analyzed to determine frequency separation of the modes as a function of the patch aspect ratio. The problem is formulated using the electric field integral equation in the spectral domain, and is solved with the method of moments. Basis functions were selected which have been used in the study of the microstrip line in the past and have been shown to converge quickly to a stable solution. Results showing the separation in the frequency of the modes and the dependence of the solution on the choice of the correct number of basis functions are presented, and comparisons with other data are made. Coupled patches are analyzed, and coupling coefficients are obtained as a function of patch separation