A Compact Ultrawideband Frequency Selective Rasorber With Hybrid 2-D and 3-D Structure

A compact ultra-wideband frequency selective rasorber (CUWFSR) with hybrid two-dimensional (2-D) and 3-D structure is proposed in this letter. The wide absorption band is obtained by the multiple resonances excited by two dipole resonators and the hybrid structure. By inserting split-ring resonator into the short dipole to bypassing the losses in the passband, an FSR with an internal transmission window and ultrawideband absorption performance is finally realized. The proposed rasorber shows a fractional bandwidth of 140.8% with a transparent window from 14.2–15.8 GHz. Then an improved design which involves two approaches of bypassing the losses of the lossy layer is also provided. Finally, an FSR with a middle passband at 15 GHz and a fractional bandwidth of 137.3% for the absorption rate better than 90% is achieved. The prototype of the improved CUWFSR is fabricated and measured for validation.