The problem of substructure characteristic modes is reformulated using a scattering matrix-based formulation, generalizing subregion characteristic mode decomposition to arbitrary computational tools. It is shown that the scattering formulation is identical to the classical formulation based on the background Green's function for lossless systems. The scattering formulation, however, opens a variety of new subregion scenarios unavailable within previous formulations, including cases with lumped or wave ports or subregions in circuits. Thanks to its scattering nature, the formulation is solver-agnostic with the possibility to utilize an arbitrary full-wave method.

翻译：采用基于散射矩阵的公式重新表述了子结构特征模式问题，将子区域特征模式分解推广至任意计算工具。研究表明，对于无耗系统，散射公式与基于背景格林函数的经典公式完全等价。然而，散射公式开辟了先前公式中无法实现的多种新子区域场景，包括集总端口、波端口或电路中的子区域情况。由于其散射本质，该公式与求解器无关，可利用任意全波方法进行计算。