Ultrabroadband Double-Sided and Dual-Tuned Active Absorber for UHF Band

In ultra-high frequency (UHF) band, conventional microwave absorbers are limited in application by their thickness or weight. In order to solve this problem, a novel double-sided and dual-tuned active frequency selective surface (AFSS) absorber for the UHF band is designed and implemented for the first time. The physical mechanism is analyzed by the equivalent circuit method (ECM) and current distribution. Non-coplanar bias circuits of p-i-n diodes and varactors are proposed and achieved by a double-sided structure. The Fano resonance introduced by double-sided structure is analyzed and suppressed. The proposed structure covers an ultrabroadband of 0.4-2.5 GHz (144.8% in fractional bandwidth) below -10 dB by changing the working states. The thickness is only λL/30 in the lowest operating frequency, and the areal density is only 1.54 kg/m2. It is worth mentioning that the structure has good angular sensitivity and can be used to complex targets for low-RCS applications.