AI 中文总结
本文提出非自由空间环境下的时间反演特征模场级定义，在两种非自由空间场景中验证该概念，表明环境数值表示不同时物理模陈述可保持不变。
AI 中文摘要
特征模在电流域中具有天然的环境解释，因为周围场景由用于构建阻抗算子的格林函数承载。一旦背景本身参与传播和反馈，散射域中同样直接的物理解释就不那么明显了。本文基于相对于规定背景的差分散射场，提出了一种场级的时间反演特征模定义。当该附加场经过时间反演并在相同背景中传播后，能再生相同的差分散射状态（相差一个标量模因子）时，就识别出了一个特征状态。该概念在两种不同的非自由空间场景中得到验证：对于有限结构背景，它再现了已确立的子结构特征模，并与同原点球面波实现一致；对于PEC半空间，它与从半空间格林函数阻抗算子获得的模一致，尽管无限平面没有天然的有限物体过渡矩阵。结果表明，即使环境的数值表示根本不同，物理模陈述仍可保持不变。
英文摘要
Characteristic modes possess a natural environmental interpretation in the current domain because the surrounding scene is carried by the Green function used to construct the impedance operator. An equally direct physical interpretation is less evident in the scattering domain once the background itself participates in propagation and feedback. This paper introduces a field-level definition of time-reversal characteristic modes based on the differential scattered field relative to a prescribed background. A characteristic state is identified when this additional field, after time reversal and propagation through the same background, regenerates the same differential scattering state up to a scalar modal factor. The concept is verified in two distinct non-free-space settings. For a finite structural background, it reproduces established substructure characteristic modes and agrees with a common-origin spherical-wave realization. For a PEC half-space, it agrees with the modes obtained from the half-space Green-function impedance operator, although the infinite plane has no natural finite-object transition matrix. The results show that the physical modal statement can remain unchanged even when the numerical representation of the environment is fundamentally different.
