CMA‐Driven Polarization Purity Enhancement in Triangular Patch Antennas With Resonance Stability

ABSTRACT This letter presents an innovative strategy to improve polarization purity in space‐constrained microstrip patch antennas using a low‐profile metal‐pin‐based superstructure. The triangular patch, an inherently compact antenna shape, suffers from high cross‐polarized field components, an issue that has been largely overlooked. Using characteristic mode analysis (CMA), the near‐field E‐field distribution of the mode reveals that the and components overlap near the apex, leading to increased cross‐polarization (XP). While latest minimally invasive method using partially shorting pins causes a 2.2% upward frequency shift, this noninvasive approach results in a 0.3% downward frequency shift, maintaining compactness and scalability. Experimental results demonstrate normalized peak XP levels of −38 dB in the E‐plane, −28 dB in the H‐plane, and −18 dB in the diagonal plane, with a peak gain of 7.2 dBi, confirming the effectiveness of the design.