A Low-Profile, Broadband Dual-Circularly-Polarized Bidirectional Folded Transmitarray

In this letter, a low-profile, broadband, and bidirec-tional folded transmitarray (Bi-FTA) is proposed. It consists of a left-hand and a right-hand circularly polarized (CP) sources and two multifunctional metasurfaces (MFMs). Two wideband CP magneto-electric (ME) dipoles acting as feeds are integrated into the upper and lower metasurfaces respectively. Both metasurfaces employ similar receiver-transmitter (Rx-Tx) structures and work as a CP selective surface (CPSS) at the Ku band. By controlling the reflection phase distributions, the incident waves undergo anomalous reflections, which are different from the specular used in conventional FTA designs. A reduced profile of the Bi-FTA is achieved. The proposed Bi-FTA is validated by experimental tests and shows satisfactory agreement with simulations. The measured peak gain values reach 22.96 and 22.83 dBic for +z direction LHCP and -z direction RHCP beams, corresponding to aperture efficiencies of 25.3% and 24.5%. The measured AR< 3 dB bandwidths are 34.1% and 35.3% for +z direction LHCP and -z direction RHCP beams. The proposed Bi-FTA features the characteristics of low profile, broadband, high gain, planar integration, and bidirectional dual CP radiation, which serve as a strong candidate for mm-wave long-distance wireless systems such as satellite communications.