Design of a Dual-Band Shared-Aperture Antenna Combining Fabry–Perot Cavity and Folded Transmitarray for X- and Ka-Bands

This work introduces a dual-band and high-gain shared-aperture antenna for X- and Ka-band applications. The antenna can produce two directive beam radiations realized by the proposed specific structure of combing a Fabry–Perot cavity antenna (FPCA) and a folded transmitarray (FTA) configuration for radiation controls at X- and Ka-bands, respectively. To hybridize these two kinds of radiation controls, it has to be achieved by the reuse of an aperture and the exploitation of distinct functions for two individual frequency bands on the same antenna body. Specifically, an aperture layer acts as a partially reflective surface (PRS) at the X-band and a polarization grating (PG) surface at the Ka-band; meanwhile, a ground layer functions as a metal reflector at the X-band and a reflecting polarizer (RP) at the Ka-band. To satisfy the above requirements, two different unit cells (UCs) are studied and analyzed to constitute the aperture layer and the ground layer for providing the controls of two radiation conditions. In addition, the feeding sources are constructed from two patch antennas (for FPCA excitation) and a 3-D printing small horn antenna (for FTA excitation). For validation, a fully functional prototype is fabricated and measured. The measured results show that the antenna realizes an effective bandwidth (for the reflection coefficient
$\le -10$
dB and the gain variation
$\le3$
dB) from 8.62 to 9.35 GHz at the X-band and from 24 to 34 GHz at the Ka-band. The measured peak realized gain is 15.5 and 23.1 dBi at two bands, respectively. The proposed design inherits the advantages of FPCA and FTA, making it promising for future wireless communication systems.