Broadband Millimeter Wave Two-Dimensional Beam Scanning Transmistarray Based on Quad-Focal Phase Re-Optimization

In this paper, a broadband two-dimensional (2-D) beam scanning transmitarray suitable for millimeter wave (mmW) band is proposed, aiming at achieving low sidelobe level (SLL). A novel polarization conversion unit cell is designed to convert the linearly polarized (LP) wave into circularly polarized (CP) wave, and through the geometric phase (GP) compensation strategy, 360° continuous phase coverage is realized by rotating the CP transmitting patch. In order to optimize the 2-D beam scanning performance, a quad-focal phase compensation scheme is introduced to reduce the scanning loss, and the phase distribution is globally optimized by combining with the multi-objective particle swarm optimization (MOPSO) algorithm, which effectively suppresses the SLL during large-angle scanning. The results show that the beam of the antenna can scan a wide angle of 34° within the bandwidth of 21 GHz − 29 GHz, the peak gain is 21.7 dBic, the axial ratio (AR) is lower than 3 dB, and the SLL is always lower than −13 dB. This design provides a high-performance solution for high-reliability applications such as satellite communication and mmW point-to-point link.