Rasorber With Wide Absorption Band Before Transmission Band (A-T Type FSR)

This paper presents a polarization-insensitive frequency selective rasorber (FSR) with wide absorption band before the transmission band. The FSR consists of two layers, the top layer is lossy layer which contains lumped resistors, while the bottom layer is a frequency selective surface (FSS) based filter layer. The proposed structure achieves a reflection coefficient less than -10 dB in the range from 3.22 GHz to 13.80 GHz (124.2%). The absorption band (80%) extends from 2.86 GHz - 10 GHz (fractional absorption bandwidth of 111%) which covers C-band fully and S- and X-band partially. Additionally, the transmission band with minimum insertion loss of 0.33 dB occurs at 12.89 GHz. The structure has a thickness of 0.09λ with respect to the lowest frequency. The surface current distribution as well as some parametric variations are studied to develop an understanding of the working principle of the proposed rasorber. Equivalent Circuit Model (ECM) is used to guide the formation of structure. The prototype has been fabricated and measured and the measured results are in accordance with the simulated results.