S-parameter analysis of multislot microstrip patch arrays: spectral domain approach

A generalised full-wave model for the evaluation of the mutual coupling in multislot-coupled microstrip patches is presented. The approach allows coupling between slots in a single patch or between patches in a finite array to be considered. The reciprocity theorem and the boundary conditions on the slots and patches are applied to the structure, and the related spectral domain integral equations are solved using Galerkin´s method of moments. Green´s function for the stratified layer is calculated by applying a transmission line approach in which equivalent circuits are defined for each stratification. Such an approach, that of expanding the vectorial equations in the transverse domain, allows a scalarisation of the problem for an arbitrary number of dielectric layers and parasitic patches to be considered. The S-matrix formalism of the N-port equivalent circuit of the general structure together with comparisons with measured reflection coefficients and mutual coupling are presented