Analysis of Microstrip Patch Antenna Array Using the Sub-Structure Characteristic Modes

The theory of characteristic modes is widely used in antenna design, but in the analysis of sub-structure, the theory of sub-structure characteristic mode (SCM) is more effective for practical applications. This paper initially introduces a method to solve the electromagnetic field problem in a space with a dielectric substrate by combining the mixed-potential integral equation (MPIE) and the discrete complex image method (DCIM). Then, we derived a method for calculating the SCM for the microstrip antenna array. Finally, the correctness of this method is verified through numerical examples.