Radiating Mode Induced Cross-Polar Source in Microstrip Patch: Identification and Solution

Abstract

A source of cross-polarized (XP) fields has been detected during investigating a square-shaped microstrip element. This letter leads to a physical insight and a conjecture that are thoroughly discussed. It focuses on the magnetic field surrounding the patch as a major contributing factor. This knowledge has been explored further to find out a solution to the newly detected XP source. An additional conduction current has been intuitively introduced in the form of a pair of coplanar coupled loops, which weakens the effective magnetic fields and results in a remarkable reduction in the XP radiations. The experiments with a set of X-band prototypes promise about 18–28 dB relative suppression compared to conventional patches. It maintains the low-profile nature of the antenna and does not disturb the ground plane either. To the best of our knowledge, the proposed mechanism is the best possible design to address all XP sources together revealing the maximum XP suppression reported so far across the orthogonal plane.