Application of Characteristic Modes to the Analysis of Scattering from Microstrip Antennas

In this work, Characteristic Modes in conjunction with Spectral Domain Moment Method are used for the efficient analysis of the scattering from arrays of arbitrarily shaped microstrip patches. In the following the Theory of Characteristic Modes for a general arrays of patches is presented. The method is tested by considering simple structure composed by two patches only but it can be extended to larger arrays. Computed results are found to be in excellent agreement with results obtained by standard MoM with subdomain basis functions. Since a small number of characteristic modes are necessary to yield a good approximation of the induced current on patches, the proposed method dramatically reduce the number of unknowns and the corresponding computational effort in the MoM solution of the problem. For this reason it allows the analysis of larger arrays with direct inversion methods.