Minimally Invasive Shorting Technique to Suppress Cross Polarization in Triangular Patch Antennas Using Characteristic Mode Analysis

In this letter, we propose a strategic mechanism to reduce cross polarization (XP) in triangular microstrip antennas. Developed from characteristic mode analysis, it identifies the orthogonal degenerate mode $ {\rm TM}_{01}$ as the cross-polarized counterpart of the dominant mode $ {\rm TM}_{10}$ and uses a pair of partially shorting pins to suppress it effectively. Unlike conventional methods, it is minimally invasive to the antenna cavity, causing minimal resonance frequency shift with no back radiation, and has no significant effect on the desired polarization of radiation. The design achieves low XP levels of −40 dB, −20 dB, and −33 dB in the E-, diagonal, and H-planes, respectively, with a broadside gain of 6.7 dBi.