Applying the Theory of Characteristic Modes to the Analysis of Finite Antenna Array elements and Ground Planes of Finite Sizes

This paper presents the characteristic mode analysis (CMA) of finite antenna array elements embedded in an array environment. The approach introduced here also incorporates the effect of a finite-sized ground plane. Two method-of-moments domain decomposition strategies are combined in this CMA enhancement, viz., the Domain Green's Function Method, as well as the Numerical Green's Function technique. The combination of these methods allows us to extract a modified impedance matrix for each of the array elements, which incorporates the mutual coupling effects from the array environment - as well as that caused by the ground plane. Characteristic mode analysis can then be applied to this altered self-interaction matrix to calculate the modified eigencurrents and eigenvalues associated with an element embedded in the array environment. The solution approach also lends itself to the analysis of both regular and irregular array geometries with disconnected and identical elements.