W-band wideband high-gain circularly polarized π-shaped antenna array with stacked parasitic patches

This paper presents a W-band circularly polarized (CP) antenna featuring aperture-coupled rotating π-shaped patches and stacked parasitic patches. The design employs a pair of symmetrical π-shaped patches, whose optimized rotation angle enables the realization of high-quality circular polarization. Compared to conventional dipole or rectangular patch structures, the π-shaped configuration provides an enhanced axial ratio (AR) bandwidth. The radiating patches are embedded within a cavity formed by substrate-integrated waveguides (SIW), with energy coupling achieved through a precisely designed slot on the SIW ground plane. To further enhance the radiation performance, a pair of stacked rectangular parasitic patches are introduced above the radiating structure. Simulation results demonstrate that the proposed antenna element achieves an 11.7 % (86–97 GHz) AR bandwidth and a peak gain of 9.7 dBic. As proof of concept, a 2 × 2 elements prototype was designed and fabricated using single-layer PCB technology. Measurements demonstrate that this array exhibits an impedance bandwidth of 11.4 % (88–98.5 GHz), an AR bandwidth of 11.3 % from 87.2 to 97.6 GHz, a gain variation between 13.8 and 15.2 dBic, and the maximum aperture efficiency reaches 74.5 %.