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

Abstract

This letter 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 (TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">02</sub> ) but leaving the fundamental radiating mode (TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sub> ) untouched. The conjecture has been successfully verified in <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S</i> -band. The approach is the simplest of all explored earlier, requiring no multiparameter optimization or fabrication complexity except requiring an additional vertical space. Antenna impedance and primary radiations are 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 tradeoff in XP suppression by 3 dB.