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An ultra‐wideband dual‐band hybrid frequency‐selective rasorber

A hybrid frequency‐selective rasorber (HFSR) with two broadband passbands and high selectivity based on serpentine line resonator (SLR) is proposed, which has low insertion loss (IL) in two passbands. The HFSR is constituted by a polarization layer, lossy layer, and lossless layer. The polarization layer is formed by a pair of arrows to realize the polarization conversion at the high‐frequency band. The lossy layer is composed of the SLR and metallic strips with four resistors, and it is adopted to absorb the electromagnetic waves and supply two broadband transparent windows. The lossless layer is a second‐order bandstop frequency‐selective surface, which consists of three metal layers of the patches and square rings. A four‐port equivalent circuit model with absorbing function is excavated to interpret the working principle of the designed HFSR. The simulation results indicate that the transmission window with 1 dB IL is achieved in 4.57–5.86 GHz and 10.65–14.43 GHz corresponding to a 24.7% and 30.1% fractional bandwidth (FBW), respectively. Besides, the co‐polarized reflection coefficients less than −10 dB are obtained from 4.57 GHz to 17.37 GHz, which has a 116.6% FBW. In addition, the physical sample of the proposed HFSR is fabricated and tested. The test results are consistent with the simulation results.