A Novel 2-bit Reconfigurable Folded Transmitarray Antenna With Low Profile and High Aperture Efficiency

This communication presents a 2-bit reconfigurable folded transmitarray (RFTA) with low profile and high aperture efficiency. Leveraging the receive–transmit architecture and the current inversion principle, a wideband 1-bit reconfigurable transmitarray (RTA) element is initially designed. Subsequently, integrating 45° phase-shifting structures into the receiving and transmitting layers achieves independent 90° phase differences, resulting in a low-loss, structurally simple 2-bit element for the RTA. Furthermore, based on the ray-tracing principle, a wideband polarization rotation reflectarray (PRRA) is designed as a reflective surface positioned beneath the RTA. This folded configuration reduces the overall antenna height to one-third of a conventional design. A low-profile RFTA prototype with 14×14 elements is designed, fabricated, and experimentally validated. The measured results closely align with simulations, achieving a peak gain of 20.44 dBi, a maximum aperture efficiency of 31.7%, and a 3 dB bandwidth of 15.46% (from 5.37 to 6.27 GHz). The proposed RFTA supports ±60° beam scanning in both the E-plane and H-plane, with SLL below −13 dB and cross-polarization levels better than −18 dB across all beam directions.