  This paper presents the theoretical analysis, design, simulations, and
experimental verification of a novel band-notched frequency-selective absorber
(BFSA) with polarization rotation function and absorption out-of-band. The BFSA
consists of multiple layers including one lossy layer, one polarization-rotary
layer and an air layer. The lossy layer is loaded with lumped resistances for
obtaining a wide absorption band. A new four-port equivalent circuit model
(ECM) with lossy layer is developed for providing theoretical analysis. The
BFSA realizes -0.41dB cross-polarization reflection at 4.5GHz. In the upper and
lower bands, the BFSA realizes a broad absorption function from 2.2GHz to
4.1GHz and 5.03GHz to 6.5GHz. The fractional bandwidth of co-polarization
reflection is 98.8% with 10dB reflection reduction. The full-wave simulation,
ECM, and experimental measurements are conducted to validate the polarization
conversion of the band-notched absorbers, and good agreement between theory and
measurement results is observed.
