Frequency Selective Rasorber with Continuous Tunable Transmission Band Based on Varactor

A novel active frequency selective rasorber (FSR) is presented in this letter, with continuous tunable transmission window unlike the earlier reported active FSR. This FSR is comprised by two-layered metal structures with an air gap in the middle. At top layer, a varactor-tunable resistive sheet structure is applied to generate a wide absorption band and a tunable passband. At bottom layer, a varactor-tunable FSS is applied to perform as bandpass filter for the final FSR. By controlling the bias voltage on varactor at different layer, the center of transmission window can be tuned from 9.87GHz to 11.22GHz continuously, and the steady band with reflection coefficient below -10dB extends from 5.65GHz to 15.39GHz.