A Broadband Frequency-Selective Rasorber with Double-Sided Absorption Bands

A broadband Frequency Selective Rasorber (FSR) with 2.5D FSS structure is proposed. The proposed FSR presents a wideband transmission window between two absorption bands. The FSR consists of a lossless periodic surface and a lossy periodic surface separated by an air layer. The lossy surface is realized by inserting a strip-type Parallel LC (P-LC) of via structure into the center of a dipole loaded with lumped-resistors. The lossless layer is a broadband bandpass frequency selective surface (FSS) consisting of two metal patches surfaces and separated by a thin layer. An equivalent circuit model (ECM) is proposed to analyze operating principle of the FSR. The fractional bandwidth for reflection less than -10 dB is about 70% and a transmission bandwidth with insertion loss of -3 dB is about 22%. The FSR perform stable frequency response from 0 to 30 degrees.