Low RCS Fabry-Perot Antenna with Water-Based Absorber

In this paper, a low radar cross section (RCS) Fabry-Perot $(\mathrm{F}-\mathrm{P})$ antenna integrated is proposed. A water-based absorber (WBA) is combined with partially reflective surface (PRS) as an asymmetric dual-layer metasurface with frequencyselective absorption and transmission properties. Based on this metasurface, an F-P resonant cavity antenna is designed to achieve high-gain radiation while reducing out-of-band RCS. Simulation results demonstrate a 6.5 dBi gain improvement compared to conventional patch antennas. Additionally, the backward 10 dB RCS reduction spans $4.5-6.3 \text{GHz}$ and $6.9-15.4 \text{GHz}$ with relative bandwidth of $\mathbf{3 3. 3 \%}$ and $\mathbf{7 6. 2 \%}$. This low-cost and eco-friendly design holds significant potential for applications requiring lowobservable platforms.