Sub-structure characteristic mode analysis of microstrip antennas using a global multi-trace formulation

TL;DR

This paper introduces a novel characteristic mode analysis method for microstrip antennas using a global multi-trace formulation, simplifying computations and improving accuracy in predicting modal behavior.

Contribution

It develops a sub-structure characteristic mode method based on a global multi-trace formulation that avoids complex multilayer Green functions and volumetric discretization.

Findings

Reliable and accurate modal predictions for microstrip antennas.

Simplified implementation compared to coupled integral equation formulations.

Effective in handling practical antenna structures with finite substrates.

Abstract

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. Compared to the coupled formulation of electric field and Poggio-Miller-Chang-Harrington-Wu-Tsai integral equations, global MTF allows for more direct 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 a reliable and accurate approach to predicting the modal behavior of electromagnetic fields on practical microstrip antennas.