Development of Wideband Transmitarray Antennas With Adaptive Bidirectional Beam Reconfigurability for mm-Wave IoT Applications

This article proposes a scheme to enable wideband and beam-reconfigurable transmitarray (TA) antennas with flexible bidirectional beams for Internet of Things (IoT) applications. The proposed scheme primarily consists of a polarization-rotation-based (PR-based) phase-shifting surface (PSS), a dielectric lens, and a feed source. By leveraging distinct frequency responses of the PR-based PSS and dielectric lens to electromagnetic (EM) waves, the proposed scheme can achieve exceptional beam reconfigurability. To validate the scheme, a bidirectional beam-reconfigurable TA antenna is developed. By mechanically rotating the feed source to tune its polarization from x- to y-polarization, the beam of the developed TA antenna transitions from a single forward beam (FB), through a bidirectional beam, and finally to a single rearward beam (RB), all remaining the same polarization. Notably, when the feed source is rotated to be 45° polarization, the forward and RBs exhibit comparable gains. The gain variation of the forward/RB approximately follows cos( $\theta $ ), where $\theta $ is the rotation angle of the feed source. Simulated results reveal that the developed TA antenna works well from 24 GHz to 28.5 GHz, exhibiting robust continuous and adaptive bidirectional beam reconfigurability with sidelobe levels below −15 dB and cross-polarization levels below −20 dB. A prototype is characterized, where the measured results align well with the simulated ones. With versatile beam-steering capabilities, the developed TA antenna is well-suited for 5G millimeter-wave (mm-wave)-enabled IoT applications, such as smart transportation systems, dual-side railway/roadway communication networks, and tunnel-based communication infrastructures.