An Ultra-wideband Multilayer Absorber Using an Equivalent Circuit-Based Approach

An ultra-wideband (UWB) absorber designed by equivalent circuit model (ECM) is presented in the paper. The structural parameters of multi-layer absorbers were calculated for full-wave simulation so as to verify the accuracy of this method. The simulation results illustrated that the ideal frequency response can be easily and quickly obtained by using ECM, such as single narrow absorption band, dual-band absorption peak and ultra-wide absorption band. A 20 × 20 quadruple-layer absorber was fabricated and tested, which obtained 10-dB radar cross section reduction (RCSR) from 2.1 GHz to 37.5 GHz with bandwidth ratio (BWR) of 17.62:1. The overall dimensions of the unit cell structure is 280×280×14 mm³ (1.96 λ_max × 1.96 λ_max × 0.098 λ_max), and the absorber exhibits stable response on conformal cylinders with central angles of 30° and 60°. Moreover, in order to reduce the influence of high-order modes above U-band, the space mapping (SM) technique was introduced to optimize the absorber’s parameters, which greatly expanded the high frequency absorption bandwidth. A 10-dB RCSR was achieved from 3 GHz to 94 GHz with BWR of 31.33:1.