Internal Resonant Characteristics Analysis of Arbitrarily Shaped Metallic Cavity with Holes Based on A Surface Integral Equation Formulation

Although the theory of characteristic modes (TCM) has been widely used for solving the external resonant (ER) problems of metallic objects, there are still some issues not fully discussed in the literature, which prevent the application in solving internal resonant (IR) problems. In this letter, a new method based on a surface integral equation (SIE) formulation is proposed to analyze IR characteristics of arbitrarily shaped metallic cavities with holes. The IR generalized eigenvalue equation with a small eigenvalue range is derived, and the discontinuous eigenvalues are corrected to theoretical zeros. As a result, the IR frequency is clearly obtained by searching for several zero eigenvalues at a same frequency. Furthermore, the IR mode is determined by defining and computing the minimum IR factor associated with exterior eigenfields of the first 40 modes. Numerical and experimental results are presented to validate the proposed method.