A novel approach to the design of multi section ultra-wideband Jaumann absorber

Abstract

A novel ultra-wideband Jaumann absorber design and analytical procedure that greatly enhance the absorption bandwidth and absorptivity level using few dielectric layers are described. The absorptivity bandwidth of the proposed structure is much better than the traditional absorbers. In Jaumann absorbers, determining resistivity of resistive sheets is a complex task and optimization techniques are generally utilized for the solution. The new contribution given in this paper is that the reflected waves from each boundary inside the dielectric layers are eliminated. Therefore, input reflection coefficient is obtained analytically using Binomial expansion without any approximation. Then a binomial matching procedure is applied to obtain the ultra-wideband absorption. Absorption enhancement is achieved by quarter wavelength dielectric slabs, resistive sheets with critical resistivities and a metallic ground plane backed final dielectric layer with high permittivity. Proposed structure is designed for normal illumination. Parallel and perpendicular polarizations are also studied for oblique incidences. Absorptivity and reflectivity variations are presented versus frequency in 0–40 GHz band for the 20 GHz design frequency for several structures. It is shown that choosing three layers backed with a final layer (εrb=20) structure gives absorptivity greater than 90% in a 6.8–33.2 GHz band region with a fractional bandwidth of 132%. CST Microwave Studio and AWR programs are used to prove the correctness of the proposed method. Great consistency is observed and demonstrated in the numerical results section.