A near-resonance decoupling approach (NRDA) for scattering solution of 3D near resonant structures

We propose an algorithm that applies the equivalence principle and the method of moments to study the multiple wave bounces in an open-ended cavity, and to reduce the iteration number for an iterative solution of the problems. The idea is to apply the equivalence principle to separate the cavity region from the exterior region and solve the cavity problem by the method of moments with a direct solver. The interior and exterior solutions are coupled via a generalized admittance matrix called the Y-matrix. As the cavity response is specified by the Y-matrix where multiple-bounce wave physics has already been incorporated, the iteration process for the exterior problem is free from having to account for multiple-bounce physics inside the cavity. Consequently, the iteration count for the exterior solution is greatly reduced. We call this method the near-resonant decoupling approach (NRDA) because it decouples the near-resonance in the cavity region from the exterior surface using the equivalence principle. It is a rigorous method and the only approximation is the result of the numerical implementation. We first describe the algorithm for a general problem and present some numerical simulation results.