Ultra-wideband Frequency Selective Absorber with Dual Independent Varactor-Tunable Notched Bands

A frequency selective absorber (FSA) with two tunable notch bands is presented in this paper. The proposed FSA is composed of an ultra-wideband absorber at the top layer to achieve an absorption band from 4.4 to 18.67 GHz and two resonators at both sides of the bottom layer to realize two tunable notch bands with about 8 GHz and 4 GHz tunable range, respectively. The biasing grids are also used at the bottom layer and metal ground to adjust the voltage of the varactors, which makes notch band tunable. In order to achieve polarization insensitive, four varactors are used on one side of the bottom layer. The simulation results show that the proposed FSA has an ultrawide absorption band and two tunable notch bands.