A Method to Reduce the Insertion Loss of Dual-Polarized Active Frequency Selective Surface

In this letter, we propose an inductor-loading method on a bias network to reduce the insertion loss (IL) of bandpass active frequency selective surface (AFSS). First, a correlation model between IL and the structural parameters of the AFSS, as well as the equivalent parameters of the varactors embedded in the AFSS, is proposed through an equivalent circuit model. Second, a low IL dual-polarized AFSS is designed and tested to validate the proposed method, guided by the above-mentioned correlation model. The test results show good agreement with the simulation results. The proposed AFSS can continuously tune its passband windows from 2.76 GHz to 5.58 GHz (with a relative bandwidth of 67.6%), and the IL remains below 1 dB over the entire tunable passband range. Additionally, the proposed AFSS features miniaturization due to the embedded inductors.