Design of Miniaturized Low Cross-Polarization Quarter-Wave Patch Antennas Using Gradient Spoof Surface Plasmon Polaritons

A quarter-wave patch antenna (QWPA) suffers from the fundamental disadvantage of a high cross-polarization level (XPL) in the H -plane. In this letter, we present a new method to overcome this issue by integrating a gradient spoof surface plasmon polariton (SSPP) structure on the side edges of QWPAs. In the proposed scheme, the SSPP structure is gradient loaded from the open end to the short end to suppress the cross-polarization radiation from the side edges. Both the single-ended and differentially-driven QWPAs are investigated and compared based on the proposed method. Simulated results indicate that SSPP-loaded QWPAs exhibit remarkable miniaturization and XPL reduction as compared with the conventional ones. To validate the feasibility of the proposed method, a differential prototype is fabricated and measured. Experimental results show that the proposed antenna achieves a distinct cross-polarization reduction of over 20 dB and a compact size of 0.088 × 0.095 λ0 ² at the center operating frequency.