A Broadband Dual-Polarization Transmission Frequency Selective Rasorber With Low Insertion Loss

A broadband, low insertion loss frequency selective rasorber (FSR) for broadband antennas is proposed. Different from the traditional method of expanding transmission bandwidth by adding multiple layers, a novel and easy to implement equivalent circuit model of the compact period lossless single layer is adopted. By inserting a LC series circuit, the equivalent circuit with a larger parallel resonance equivalent inductance has been realized and a topology is adopted to achieve the desired broadband transmission performance, offering a new approach to the design of lossless layer. By incorporating circular spiral parallel resonators (CSPRs) and adopting a 2.5-D design in the lossy layer, a compact topology with broadband transmission is achieved. When cascading the lossy and lossless layer, the resulting FSR achieves a -1 dB transmission over the 6.31–13.84 GHz range, corresponding to a relative bandwidth of 74.7%. Additionally, the -0.5 dB transmission band spans 7.43–13.36 GHz, with a relative bandwidth of 57%. A prototype of the proposed FSR was fabricated and measured, verifying the feasibility of the design for broadband transmission FSR.