Multibeam Quad-Polarized Transmit-Array Antenna With Arbitrary Radiation Direction for Vehicle Communication via Generalized Phase Superposition

A four-beam, quad-polarized transmit-array (TA) antenna is proposed, which can simultaneously radiate x-polarized (XP), y-polarized (YP), left-hand circularly polarized (LHCP), and right-hand circularly polarized (RHCP) high-gain beams. First, a quasi-anisotropic element is designed based on the stacked cross-shaped patch structure, and its phase response for XP and YP electromagnetic (EM) waves can be approximately independently adjusted. Then, the TA can radiate different linear polarized (LP) beams based on various XP and YP phase distributions on the aperture. Next, LHCP and RHCP beams can be generated by making the XP and YP beams radiate in the same direction with a ±90° transmission phase difference. Third, the generalized phase superposition method is applied so that the proposed design can obtain the multibeam multipolarization radiation characteristics. Finally, to improve the phase compensation accuracy of the metasurface aperture, an optimized aperture deployment approach is proposed, which can quickly find the optimal element distribution and reduce the phase error between the actual phase and the target phase on the aperture. A four-beam quad-polarized TA with $20\times 20$ elements is designed, fabricated, and measured. The measured 1-dB gain bandwidth of each beam is about 5%, and the peak aperture efficiency is 26.99%, which proves that the proposed TA has stable multibeam and multipolarization multiplexing characteristics.