W-Band Circularly Polarized High-Gain Antenna Array With Sequentially Rotated High-Order Mode Cavity Excitation

This letter presents a wideband high-gain circularly polarized (CP) antenna array designed for W-band applications. First, a 2 × 2-element subarray is proposed, where each radiating element consists of aperture-coupled C-patches. To reduce transmission loss and maintain compactness, the C-patches are fed by high-order mode (TE₂₂₀) substrate-integrated cavity (SIC) rather than the bulky power divider. More importantly, the 2 × 2 SICs are sequentially rotated (SR) to achieve broadband circular polarization with high purity. Then, a 4 × 4 CP antenna array based on the SR SIC is demonstrated to achieve higher gain and fabricated as well as measured for the concept verification. The simulated and measured results agree well. The measurement results demonstrated that the proposed design could achieve a −10 dB impedance bandwidth of 17.5% (88.5 GHz to 105 GHz). Meanwhile, the 3 dB axial ratio bandwidth covers the impedance bandwidth of more than 21.3% (85 GHz to 105 GHz). The peak gain reaches 20.8 dBic at 96 GHz, and the peak aperture efficiency up to 63.9%.