Analysis and Efficient Design of Sub-THz Transmitarrays with Three Anisotropic Layers

In this paper, we study the transmission behavior of a three-layer anisotropic frequency selective surface with applications to the optimal design of transmitarray antennas. We theoretically investigate the depolarizing properties of the middle layer and derive a condition to achieve any transmission phase and at the same time zero insertion loss. Lastly, a 3-bit 40×40 transmitarray is designed at 300 GHz, based on the proposed approach. The antenna attains a maximum gain of 35.1 dBi with an aperture efficiency of 64.8%, which is only 0.5 dB less than the ideal case of a transmitarray having perfect transmission and phase compensation.