Design, Modeling and Analysis of Low Cross Polarization Level Low Radar Cross Section Conformal Ultra Wideband Absorber based on Resistive Metasurface

In this paper, a low cross-polarization level, low radar cross section (RCS), conformal, ultra-wideband, polarizationinsensitive absorber utilizing sinusoidal periphery annular ring (SPAR) resonator based novel resistive metasurface is presented. The proposed absorber operates with more than 90% absorptivity over the frequency range 7.68 GHz-24.90 GHz encompassing X-, Ku- and major portion of K-bands. The absorber consists of two sinusoidal peripheries annular rings embedded with lumped resistors, placed on top of a 0.1 mm thin low cost FR-4 substrate which is supported by metal backed foam. The sinusoidal periphery on the annular rings improves the absorption bandwidth and miniaturizes the proposed structure. Cross-polarized reflected component from the absorber is also investigated and included in the estimation of absorptivity to validate that the proposed structure functions as an absorber and not as a reflective type polarization converter. An equivalent circuit analysis based on the transmission line model is also presented. Novelty of the proposed article's lies in the design approach for the proposed absorber in which flexibility is incorporated to choose unit cell geometrical parameters as per the limiting frequencies (upper and lower) of desired band along with some miniaturization aspects of the absorbing structure. Furthermore, 10 dB RCS reduction is discussed, and the formula is derived by including cross-polarized reflection component of the incident wave in estimation. The proposed absorber is validated through theoretical, simulation, and experimental studies for planar and conformal applications.