Low-Profile Wideband 1-bit Reconfigurable Transmitarray With 2-D Beam-Scanning Capacity

In this article, a folded low-profile wideband 1-bit reconfigurable transmitarray (RTA) with 2-D beam-scanning capacity is proposed. To reduce the profile of the whole RTA, the ray tracking mechanism and the feed optimization are introduced. A 1-bit wideband RTA element with polarization selection function and polarization rotation function is designed based on a regular hexagonal resonant patch and p-i-n diodes. Furthermore, a specially designed waveguide structure is fabricated to verify the performance of the RTA element. To achieve the low-profile design, a wideband polarization rotation reflectarray (PRRA) element acting as the reflecting surface is proposed, and a
$2\times $
2 U-slotted planar patch antenna is designed to replace the horn. With these designs, the profile can be compressed by two-thirds compared with the conventional space-fed architecture. A
$16\times16$
-elements low-profile RTA is designed and fabricated. The measured and simulated radiation patterns are in good agreement. The measured peak gain is 19.6 dB, corresponding to an aperture efficiency of 13.8%, and the measured 3 dB gain bandwidth is 17.5% (from 15.1 to 18 GHz). Good scanning performance with ±60° scanning coverage in both principal planes has been obtained, and the scan losses are 3.97 and 4.15 dB, respectively. Besides, the measured sidelobe levels (SLLs) and cross-polarization levels remain better than −15 and −20 dB, respectively, at all beam directions.