Band-notched frequency-selective absorber with linear polarization rotation function

This article presents a novel band-notched frequency-selective absorber (BFSA) with linear polarization rotation function in-band and absorption out-of-band. When used as an antenna reflector, the BFSA can not only reduce RCS outside of the antenna's working band, but also reduce co-polarized RCS within the working band and improve cross-polarized reflection. The BFSA realizes -0.41 dB linear polarization-rotating reflection at 4.5 GHz. In the upper and lower bands, the BFSA realizes a broad absorption function from 2.2 GHz to 4.1 GHz and 5.03 GHz to 6.5 GHz. The fractional bandwidth of linear co-polarization reflection is 98.8% with 10 dB reflection reduction. The experimental measurements are conducted to validate the polarization conversion of the band-notched absorbers, and good agreement between theory and measurement results is observed.