A Low-Profile Metal-Only Folded Transmitarray Antenna Based on Asymmetric Transmission Chiral Metasurface

This communication presents a low-profile and low-cost metal-only folded transmitarray antenna (FTA) based on chiral metasurface, which reduces the profile by simultaneously folding the propagation path of the waves and simplifying the structure of transmitarray. Unlike traditional elements of transmitarrays, the proposed element consists of only two metal layers without any vertical metal structures between the layers, which achieves high transmission efficiency and 360° phase shift capability. Furthermore, a metal-only reflective plate with polarization conversion characteristics is introduced to reduce the profile of the antenna. Due to the polarization regulation ability of the element, the propagation path of incident waves is folded twice to reduce the FTA’s profile to 1/3 of traditional transmitarray antennas (TAs). Consequently, the heights of the array and the whole antenna are only <inline-formula> <tex-math notation="LaTeX">$0.14\lambda _{0}$ </tex-math></inline-formula> and <inline-formula> <tex-math notation="LaTeX">$6.88\lambda _{0}$ </tex-math></inline-formula> (including the feed source), respectively. A prototype operating at 11.45–13.25 GHz is fabricated and measured. The measured maximum gain of the antenna is 27 dBi, with a total efficiency of 35.3%. These results indicate that the proposed antenna significantly reduces the profile, cost, and processing complexity while ensuring total efficiency and bandwidth. The proposed metal-only FTA has significant applications in some scenarios requiring low profile, low cost, and high-power capacity.