A Compact Dual-Band and High-Gain Antenna with a Large Frequency Ratio

This paper presents a compact dual-band and high-gain shared- aperture antenna for sub-6 GHz and K-band application. At the lower band, a Fabry-Perot cavity antenna (FPCA) works as the radiator and a folded reflectarray (FRA) operates at the higher band. To hybridize these two kinds of antennas together and achieve a high aperture reuse efficiency, the unit cell (UC) constituting the upper aperture should be able to partially reflect the incident wave at the lower band and act as the polarization grating (PG) at the higher band; for unit cell constituting the lower aperture, it needs to function as the metal ground at the lower band while twist the polarization of the reflective wave and implement the phase compensation at the higher band. To satisfy the above requirements, two kinds of unit cells are studied, analyzed and used to construct a shared-aperture antenna. The results show that the antenna realizes an effective bandwidth (for reflection coefficient = -10 dB and gain variation <= 3 dB) from 5.62 to 5.94 GHz at the lower band, and from 19.5 to 26 GHz at the higher band. The peak gain is 16 dBi and 27.4 dBi at two bands, respectively.