A Wideband Tunable Active Absorptive Radome

A wideband tunable active frequency selective surface absorber structure is studied in this paper. The band with reflection coefficient below -10dB extends from 0.9GHz to 5.4GHz, about six octave. The thickness of this absorptive radome is 20mm. This structure consists of three layers, the bottom is a metal reflector. The middle layer is a tunable active frequency selective surface absorber realized by varactor diode. The middle layer and the bottom layer is used to tune the absorption band from 0.9GHz to 2GHz, and it has the same reflection characteristics with metal plate from 2GHz to 5.4GHz. The upper layer is double square-loop with resistance, it is used to absorb waves from 2GHz to 5.4GHz. Therefore, the structure can achieve wideband wave absorption effect from 0.9GHz to 5.4GHz. The simulation results show that with the increase of incident angle, the absorbing property is deteriorating, but it still has certain wave absorbing property.