Design of miniaturized and highly selective frequency selective rasorber based on compact spiral resonator

A miniaturized, high-selectivity, wideband A-T-A frequency selective rasorber (FSR) based on compact spiral resonators (CSR) is proposed here. The lossy layer of the FSR consists of the CSR and a Jerusalem cross, with four resistors soldered onto the surface. The underlying layer is a bandpass frequency selective surface (FSS) with an extremely narrow slit. The dimensions of the FSR unit are only 0.079 lambda L x 0.079 lambda L x 0.078 lambda L. The extremely narrow-slitted FSS and CSR together provide a narrowband frequency response, enhancing the selectivity of the FSR. Additionally, a prototype of an FSR was fabricated and tested, achieving results highly consistent with simulations.