Folded Transmitarray Antenna via Independent Amplitude/Phase Control With Low Side-Lobe for Millimeter-Wave Communication

A low-profile folded transmitarray antenna (FTA) with independent amplitude and phase control is proposed for the applications of millimeter-wave (mm-wave) communication. The proposed FTA is composed of three functional parts, i.e., an independent amplitude-phase controlling metasurface (MS) on the top, a polarization-converter on the bottom, and a feeding antenna. Particularly, by using spatially designed amplitude on the aperture of the top MS with the specification of the Taylor distribution, much lower side-lobe levels (SLLs) could be effectively realized. The ray-tracing method is used to reduce the profile height and integrate both the feeding antenna and the polarization converter. The proposed FTA, which is fully integrated and fabricated using low-cost printed circuit board (PCB) technology, is verified by the theoretical analysis, full-wave simulation and experimental measurements of a prototype covering the entire 5G mm-wave n257 bands (26.5 to 29.5 GHz). The measured results show that the proposed FTA has a 3 dB gain bandwidth of 19% from 24.8 to 30 GHz and a peak gain of 21.08 dBi with an aperture efficiency of 18.3%. Especially, compared to traditional FTAs with phase modulations only, the proposed FTA performs an average SLLs reduction of more than 5.0 dB. The simulated and measured results coincide to confirm the feature and effectiveness of the FTA with the excellent performance.