Frequency-Selective Rasorber with Tunable Passband Based on Tripole Elements

This paper presents a frequency-selective rasorber which has two absorption bands on the both sides of a tunable passband. An original rasorber with fixed-passband is designed by cascading of an absorptive frequency-selective surface (FSS) and a lossless bandpass FSS. The absorptive FSS is realized with tripole elements and the lossless bandpass FSS is achieved with tripole ring slot. Varactors and biasing networks are inserted for tuning the passband. The simulated results show that the center frequency of passband is altered from 4.5 to 6 GHz with the capacitance of varactors changing from 0.2 to 0 pF. The frequency-selective rasorber with a fixed-passband is fabricated and measured to verify the design.