A novel wideband absorptive frequency selective surface based on circuit analog absorber

In this paper, a single polarized absorptive frequency selective surface (AFSS) with ultra-wide transmission band and broad absorption band has been proposed numerically and experimentally. Based on the principle of circuit analog absorber (CAA), the proposed wideband AFSS is realized via replacing the ground plane with a band-stop frequency selective sturcture. The proposed AFSS is finally a hybrid structure composed of a wideband lossy frequency selective surface (FSS) in the top and a 3D band-stop frequency selective structure in the bottom. The wideband lossy FSS with thinner profile in the top is realized by utilizing a low pass capacitive elements to compensate the equivalent load inductance arising from the air space that is less than quarter wavelength installing between FSS and ground plane, and the low pass capactive lossy FSS is synthesized using " Gong" -shaped patterns with lumped resistors. Meanwhile, the unit cell of 3D frequency selective structure consists of two electrical coupling C-shaped patterns is investigated to achieve a wide stop band with high selectivity, which can be equivalent to the ground plane in the absorption band. By cascading the wideband lossy FSS and the 3D band-stop frequency selective structure, a thinner hybrid AFSS is presented with ultrawide transmission band and broad absorption band. The results obtained from simulation shown that an absorption band with absorptivity above 90% is obtained from 6.6 to 11.6 GHz, and the 1 dB transmisson band is from 1 to 3.5 GHz with minimum insertion loss of 0.21 dB. Moreover, the performance can be guaranteed for TE-polarized oblique incidence up to 30 degrees . Finally, a prototype is fabricated to validate its performance, the measured results shown that the 1 dB transmission band ranges from 1 to 3.5 GHz, and the absorption band is operating from 6.3 to 11 GHz at normal TE-polarized incidence. A good agreement between the experiment and simulation results is achieved, which verifies the effectiveness of the design.