A Low-Profile and Beam-Steerable Transmitarray Antenna: Design, Fabrication, and Measurement [Antenna Applications Corner]

This paper describes the design, fabrication, and measurement of a low-profile and beam-steerable transmitarray (TA) antenna based on ray-folding principles. The proposed TA antenna consists of a planar feeding source, phase-shifting surfaces, and a metal plate as a reflector. The electromagnetic (EM) wave radiating from the planar feeding source would be reflected firstly by the metal plate, and then propagate through the phase-shifting surfaces to achieve a focused beam at broadside. In this configuration, the profile of the proposed TA antenna is decreased to half compared with a conventional TA antenna. To demonstrate the superiorities of the proposed TA antenna, the reflection coefficients, radiation patterns, and realized gains of three antennas, namely, the proposed TA antenna, a reflectarray (RA) antenna for reference, and a TA antenna for reference are simulated, compared, discussed, and measured. It is concluded that the proposed TA antenna has a comparable realized gain and lower profile. The simulated results reveal the proposed TA antenna has a realized gain of 24.8 dBi at 28 GHz with a profile of 20 mm (1.87λ0 at 28 GHz), resulting in an aperture efficiency of 31.3 %, which are experimentally verified. The proposed TA antenna is also expanded to achieve beam steering. A prototype of a beam-steerable TA antenna with five beams is fabricated and measured, where main beams at ± 16o, ± 8o, 0o are observed with a gain variation of 2.4 dB and a broadside gain of 24.0 dBi corresponding to an aperture efficiency of 27 % at 27.2 GHz.