A characteristic mode (CM) method that relies on a global multi-trace formulation (MTF) of surface integral equations is proposed to compute the modes and the resonance frequencies of microstrip patch antennas with finite dielectric substrates and ground planes. Unlike the traditional full-structure CM methods, the global MTF allows for implementation of a sub-structure CM method. This is achieved by representing the coupling of the electromagnetic fields on the substrate and ground plane in the form of a numerical Green function matrix, which yields a more compact generalized eigenvalue equation. The resulting sub-structure CM method avoids the cumbersome computation of the multilayered medium Green function (unlike the CM methods that rely on mixed-potential integral equations) and the volumetric discretization of the substrate (unlike the CM methods that rely on volume-surface integral equations), and numerical results show that it is more accurate than full-structure CM methods in predicting the modal behavior of electromagnetic fields on practical microstrip antennas.

翻译：提出了一种基于表面积分方程全局多迹公式(MTF)的特征模式(CM)方法，用于计算具有有限介质基板和接地板的微带贴片天线的模式及其谐振频率。与传统的全结构CM方法不同，全局MTF支持实现子结构CM方法。该方法通过将基板和接地板上电磁场的耦合表示为数值格林函数矩阵的形式，从而得到更为紧凑的广义特征值方程。最终的子结构CM方法既避免了需要多层介质格林函数计算的繁琐过程（不同于基于混合位积分方程的CM方法），也无需对基板进行体离散化处理（不同于基于体-表面积分方程的CM方法）。数值结果表明，在实际微带天线的电磁场模态行为预测方面，该方法比全结构CM方法具有更高的精度。