Low-RCS Reflectarray Antenna Based on Frequency Selective Rasorber

We design a low-radar-cross-section (RCS) planar reflectarray antenna by using a frequency selective rasorber (FSR). Due to the metal-backed configuration and focusing effect of the phase modulation surface, the RCS of a planar reflectarray antenna is generally quite high. Besides, an out-of-band signal focused by the reflector may cause serious interference to the system and affect the performance of facilities. To reduce the RCS of the reflectarray and suppress out-of-band interference, the FSR with a transmission window is designed and covered in front of the reflectarray. Simulation results show that the out-of-band RCS of the reflectarray is significantly reduced without affecting the radiation performance. To verify the benefits of the structure in antenna's RCS reduction (RCSR) and interference suppression, the reflectarray, the FSR, and the horn antenna work at 8.9 GHz are designed, fabricated, and measured. Measurement results show that the gain of the proposed low-RCS reflectarray antenna has only 0.3 dB decrease compared with the gain of non-FSR configuration. Meanwhile, the RCS of the proposed structure is remarkably reduced, and the -10 dB RCSR is obtained from 4 to 12.5 GHz.