Efficient analysis of mircrostrip antenna arrays through using characteristic modes

An efficient method is proposed for the radiation solution of microstrip antenna arrays made of identical elements. This method is based on the formula of volume surface integral equation (VSIE) solved by the method of moments (MoM). The characteristic modes (CM) of the single element are applied as entire-domain basis functions to reduce the impedance matrix of the whole array. It allows the analysis of large arrays with direct inversion methods. A source mode (SM) obtained by subtracting several dominant CMs from the exact current of a single element is added to expand the current due to the slow convergence when using CMs to approximate the current excited by a delta gap source. Numerical results have shown a good agreement between the solution of MoM and the present method. Meanwhile, the memory requirements and computational time of the proposed method reduce obviously.