Frequency-Selective Rasorber for Wideband Transmission Based on Hybrid Resistive Sheet With Harmonic Suppression

To break through the limitation of harmonic loss on transmission bandwidth, a novel frequency-selective rasorber (FSR) for wideband transmission is present in this article. The FSR is composed of two subsets: an absorption-transmission (A-T) rasorber and a transmission-absorption (T-A) rasorber. The A-T rasorber generates a lower absorption band with harmonic suppression, resulting in a multioctave low insertion loss (IL) transmission window. The harmonic suppression principle of the resistive sheet of the A-T rasorber is described and analyzed in detail, and the corresponding equivalent circuit model is developed to further comprehend the underlying mechanism. The T-A rasorber is designed for a customized upper absorption band. By combining the two subsets, an absorption-transmission-absorption rasorber with wide and low IL passband is obtained. Simulation shows that the −1 dB passband located within the absorption bands ranges from 5.93 to 18.34 GHz with 102% relative bandwidth. Then a linear polarization insensitive FSR extended from the proposed one is discussed. Finally, a prototype with 16 × 16 unit cells is fabricated and measured to validate the design.