A Low-RCS Multifunctional Reflectarray Antenna Based on Frequency Selective Rasorber

This paper presents a multifunctional reflectarray antenna (MRA) featuring selective in-band switchable polarization and out-of-band radar cross-section (RCS) reduction. To mitigate the strong out-of-band reflections inherent in conventional reflectarray antennas, a frequency-selective rasorber is designed as the top-layer metasurface, providing a transmission passband for in-band operation and dual broadband absorption bands for out-of-band RCS reduction. The bottom-layer metasurface is a 1-bit polarization conversion metasurface designed to reflectively convert incident linear polarization into left-handed circular polarization (LHCP), right-handed circular polarization (RHCP), or maintain the incident linearly polarized state. By integrating a dual-polarized bow-tie dipole antenna, the proposed MRA achieves a compact profile of 1.56λ0 without compromising the radiation performance. A prototype of MRA is fabricated and measured, demonstrating good agreement between simulation and experimental results. Experimental results show that for both the LHCP and the RHCP, the MRA achieves a peak realized gain of 16.2 dBic at 7 GHz, with an aperture efficiency of 29.38%, and a 1 dB gain bandwidth of 13.72%. For linearly polarized radiation, the peak realized gain reaches 16.4 dBi at the same frequency, accompanied by an aperture efficiency of 30.77% and a 1 dB gain bandwidth of 12.89%. Furthermore, the monostatic RCS is reduced by more than 10 dB in two frequency bands: 3.3–6.3 GHz (62.5%) and 8.8–11.8 GHz (29.13%).