A Novel Broadband Polarization Insensitive Circuit Analog Absorber (CAA) for Radar Cross Section (RCS) Reduction Applications at X. and Ku-Bands

Abstract

A simple broadband polarization-insensitive Circuit Analog Absorber (CAA) is proposed in this work. The unitcell comprises two Frequency Selective Surfaces (FSSs). The top FSS is an eight-lumped resistor-loaded corner modified square loop resonator, and the bottom is a circular ring with middle cuts. Both the FSS were printed on the thin FR-4 dielectric substrates, which were separated by an air-spacer. The proposed design exhibits 90% absorptivity from 6.72 GHz to 19.82 GHz (98.7% fractional bandwidth) with almost 95% absorption from 7.54 GHz to 17.85 GHz covering the whole X and Ku-bands. Because of four-fold symmetry exist in the design, it is polarization insensitive for different polarization angles (ø) in the azimuthal plane, and it is obliquely stable up to 45° for both Transverse Magnetic (TM) and Transverse Electric (TE) modes in the elevation plane. The design is compact with a total thickness of0.081λL and a cell periodicity of 0.164λL, where λL is the free-space wavelength corresponding to the absorption bandwidth's lowest frequency. The proposed design's Radar Cross Section (RCS) ability is observed, and it shows a peak RCS reduction of 7.4 dBsm under normal incidence. According to the author's expertise, the design can be utilized in a variety of real-time applications.