An Ultrathin Quad-band Microwave Absorber with Small Frequency Ratio

This paper presents an ultrathin quad band absorber having distinct absorptivity peaks of 99.5, 98.1, 98.6 and 99.8% at 4.38, 5.68, 6.86 and 7.6 GHz respectively. The absorber constructed with a combination of loop type elements is designed to provide four closely spaced operational bands in the C band. The frequency ratio between adjacent absorption peaks is maintained close to unity. The proposed absorber is polarization independent with angular stability upto 45°. The metamaterial nature of the absorber is proved. The effectiveness of the absorber for RCS reduction is also evaluated. A prototype is fabricated and the measured results exhibit good concordance with the simulated results.