Shrinking Profile of Fabry–Perot Cavity Antennas With Stratified Metasurfaces: Accurate Equivalent Circuit Design and Broadband High-Gain Performance

Broadband high-gain Fabry-Perot cavity (FPC) antennas require multilayer partially reflective surfaces (PRSs), but there are often air gaps between two adjacent layers greatly increasing the profile and instability of the antenna. To shrink their profile by eliminating the air gaps, an equivalent circuit analysis considering interlayer coupling and employing accurate analytical calculation of the circuit element values with physical dimensions is proposed in this letter. Based on the proposed method, a compact stratified metasurface is designed as the PRS. The optimized results by our analytical approach are in an excellent agreement with the full-wave simulation ones. Moreover, a low-profile broadband high-gain FPC antenna comprising a waveguide-feed slot antenna inside the ground and the proposed stratified PRS is presented. A proof-of-concept prototype is fabricated, and the measurement shows that a 14% 3 dB gain bandwidth with a central operating frequency of 19 GHz and maximum gain of 19.4 dBi is achieved, which in turn validates our method. The total profile of the antenna is close to a half-wavelength, making it an excellent candidate for miniaturized automotive radars and modern communications.