Design of switchable dual-band frequency-selective rasorber/absorber

This article presents a novel design of a switchable dual-band frequency-selective rasorber/absorber, which is a double-layered structure. At the top layer, two electric-field-coupled resonators with different size are utilized to achieve two transmission bands. At the bottom, to achieve low insertion loss, the frequency-selective surface based on slots with different lengths resonates at the same frequency as the top layer. By controlling the bias voltage of PIN diodes, the structure can be switched between dual-band rasorber/absorber mode. The operating principle is analyzed by an equivalent circuit model. When the diodes are in the OFF state, it shows two transmission bands at 2.86 GHz with 0.47 dB insertion loss and 3.61 GHz with 1.04 dB insertion loss. When the diodes are in the ON state, it exhibits a wide fractional absorption bandwidth of 90.1%. Meanwhile, the proposed dual-band switchable structure is fabricated and measured. There is a good agreement between simulation and measurement.