Design and fabrication of broadband microwave absorber using CISR sheets in 2.5 to 8.2 GHz range

Complex permittivity and complex permeability of carbonyl iron filled silicon rubber (CISR) sheets are evaluated using coaxial air line method and Rectangular Dielectric Waveguide (RDWG) systems in 2.5 to 4 GHz and 3.95 to 8.2 GHz frequency bands, respectively. Genetic Algorithm (GA) optimization technique and polynomial approximation technique are used for design of multilayer microwave absorbers using CISR sheets. In this paper, two-layer broadband microwave absorber is designed in frequency range of 2.5 to 8.2 GHz using CISR sheets. Top and bottom layers of CISR sheets are prepared with 0% and 50% of Carbonyl Iron (CI) powder by volume in CISR sheets, respectively. Measured as well as simulated reflectivity of two-layer microwave absorber are better than 10 dB at normal incidence in the frequency range of 2.5-8.2 GHz. For oblique incidence from 0 degrees to 40 degrees for TE and TM polarizations, simulated reflectivity of are less than -10 dB over 3 to 8 GHz range..