Miniaturized frequency selective rasorber with absorption in S–C band and transmission in X band

A miniaturized frequency selective rasorber (FSR) that has a wide absorption band in the S–C band and a wide transmission band based on X-band is presented in this paper. The FSR consists of a lossy layer loaded with lumped resistors and a bandpass layer with a three-screen cascade structure, which has the advantages of low insertion loss, wide passband bandwidth, and stable structural performance in the operating band. The rectangular spiral resonant (RSR) is loaded in the middle of the four arms of the cross to form a lossy layer. The aggregate resistance is loaded between the units to form a closed loop, which will absorb the detection signal and thus greatly reduce the radar cross section (RCS). The bandpass layer is divided into three layers, with two identical square patches coupled with a layer of complementary cross grids to form a multi-order bandpass filter. Furthermore, the operating mechanism of low absorption and high transmission is analyzed and verified based on equivalent circuit theory and impedance matching theory. The simulation results show that the 1 dB transmission band of the FSR is 8.0–12.5 GHz and the 10 dB absorption band is 2.8–6.6 GHz. The highest transmittance reaches over 97% at 10.0–11.5 GHz and the lowest insertion loss is 0.012 dB. It has important theoretical reference value and great application in the field of the new stealthy radome.