An Ultralow‐Profile Metal‐Only Folded Transmitarray Antenna With Integration of a Planar Feed

ABSTRACT

This letter presents an ultralow‐profile metal‐only folded transmitarray (MOFTA) with integration of a planar feed. The proposed antenna consists of a top transmitarray that reflects y ‐polarized waves while transmitting x ‐polarized waves and converting them to a y ‐polarized focused beam, a bottom reflectarray that provides polarization conversion and phase compensation, and a metal‐only patch embedded in the middle of the reflectarray as a feed. Based on the ray‐tracing principle and utilizing extra phase compensation provided by the reflectarray, the overall profile height is shrunk to one‐fifth of the original focal length. In addition, the planar feed is co‐designed with the reflectarray, resulting in a more compact configuration. To verify the feasibility and advantages of the proposed design, an ultralow‐profile MOFTA operating in the X‐band is designed, fabricated, and measured. The testing results show that the maximum aperture efficiency reaches 21.3%, and a 3 dB gain bandwidth is 15%, demonstrating its good potential for high‐gain applications requiring a low‐profile structure and steady behavior.