Mitigating Unwanted Mode in a Microstrip Patch by a Simpler Technique to Reduce Cross-Polarized Fields over the Orthogonal Plane

Abstract

This work explores a new concept for the first time to control a specific unwanted higher mode in a microstrip patch with a target to reduce its cross-polarized (XP) radiation over the orthogonal plane. A strategic metal pole has been introduced to control the modal current of an orthogonal higher mode (TM02) but leaving the fundamental radiating mode (TM10) untouched. The conjecture has been successfully verified in S-band. The approach is the simplest of all explored earlier, requiring no multi-parameter optimization or fabrication complexity except requiring an additional vertical space. Antenna impedance and primary radiations are absolutely insensitive to this technique but it ensures 11dB XP suppression over the orthogonal plane. The pole height can be reduced by 40-63% by accepting a trade-off in XP suppression by 3dB.