High-Gain Fabry-Pérot Antenna with Reconfigurable Scattering Patterns Based on Varactor Diodes

In this paper, a low radar cross section (RCS) and high-gain Fabry-Perot (F-P) antenna with reconfigurable scattering beams based on varactor diodes is proposed. The partially reflecting surface (PRS) of the proposed F-P antenna is composed of an anisotropic frequency-selective absorber (AFSA) and an active phase gradient metasurface loaded with varactor diodes. The proposed AFSA can absorb the cross-polarized wave and make the co-polarized wave pass through. The in-band co-polarized scattering beams can be tuned continuously with stable radiation beams by changing the capacitance of the varactor diodes. Therefore, the proposed device can reduce the RCS for in-band co-polarized and cross-polarized incident wave. Moreover, taking advantages of the path difference between the radiating and scattering waves, the gain enhancement and RCS reduction are realized simultaneously. Simulated results show that the scattering beam can be tuned dynamically from -40° to 40° with a maximum gain enhancement of 7.2 dB. The co-polarized in-band reconfigurable scattering beam and the stable gain enhancement are firstly implemented in a single antenna. A significant monostatic RCS reduction is obtained for the co- and cross-polarized wave in the frequency band of 5.5-7 GHz with a maximum reduction value of 20 dB. The experimental and simulated results are in good agreement.