A Low-Profile and High-Gain Antenna With Bidirectional Beams Enabled by Integrating Folded Transmitarray and Fabry–Perot Cavity

A millimeter-wave (mm-wave) high-gain antenna with bidirectional radiation is proposed in this article. It is the first attempt to combine a folded transmitarray (FTA) and a Fabry-Perot cavity (FPC) antenna to achieve bidirectional beams. By using this method, bidirectional radiation can be achieved while keeping a relative low profile when compared to traditional TA antennas. The proposed antenna consists of a dual-polarized (DP) feeding source, a single-layered partially reflective surface (PRS), and a bottom metasurface. By adding metal grids on the bottom surface of the PRS, it can partially reflect the x-polarized electromagnetic (EM) wave and fully reflect the y-polarized EM wave simultaneously. The bottom metasurface can also reflect x-polarized EM wave and transmit y-polarized EM wave. Hence, for the DP feeding source, when the x-polarized wave is generated, forward radiation is realized by FPC effect. When the y-polarized wave is generated, the backward radiation characteristic is achieved due to the FTA function. For validation, a prototype with a center frequency of 35 GHz is designed, fabricated, and measured. The proposed antenna can achieve 18 and 21 dBi in the bidirectional directions, respectively. The proposed design is a candidate for mm-wave long-distance wireless systems that require low profile and high communication flexibility.