Dual-Band Shared-Aperture Single-Layer Partially Reflective Surface Antenna With Flexible Frequency Ratio

Dual-band shared-aperture Fabry-Pérot cavity (DS-FPC) antennas with single-layer partially reflective surface (PRS) are inherently limited in the achievable frequency ratio. This paper analyzes such antennas to derive the feasible range of frequency ratio and thereafter proposes a dual-band shared-aperture antenna that can fill the frequency ratio gap. The novel design integrates a short backfire antenna for the low band (LB) and a Fabry-Pérot cavity (FPC) antenna for the high band (HB), utilizing a shared single-layer PRS and a parasitic element. To demonstrate the effectiveness of the solution, a prototype was designed and fabricated for the frequency ratio of 1.64, representing the extreme limit of the infeasible frequency ratio gap for conventional DS-FPC antennas with single-layer PRS. The overall height of the antenna is 0.36 and 0.59 wavelength in LB and HB, respectively. The prototype achieves 7.3% and 6.7% of measured overlapping 10dB impedance bandwidth and 3dB realized gain bandwidth, significantly outperforming other designs with single-layer PRS. Moreover, it generally offers simpler structure, lower profile, as well as more balanced overlapping bandwidths when compared to other designs with multi-layer PRS.