Active Frequency-Selective Rasorber with Wide Range Passband Continuous Tunability

In this paper, an active frequency-selective rasorber (AFSR) with a wide tunable range of passband windows is proposed. The proposed AFSR includes an absorption layer, a frequency selective layer, and an air spacer between them. The absorption layer is embedded with resistors to aid in the absorption of out-of-band unprofitable signals, and the frequency selective layer is designed to provide tunable transmission passbands through in-band beneficial signals. A design method for the AFSR embedded with varactors based on equivalent circuit model is proposed. Driven by an applied voltage, the transmission passband of the proposed AFSR can be shifted from 3.4 to 6.9 GHz. The absorption bandwidth covers from 6.4 to 14.1 GHz. In addition, the proposed AFSR exhibits stable performances up to 45 degrees angle of incidence wave. The measurement results of the fabricated prototype are in good agreement with the simulation results. This work provides a feasible solution for flexible simultaneous regulation of radiation and scattering.