Design and Fabrication of Broadband Microwave Absorber using FSS embedded in CISR sheets

A broadband microwave absorber was designed and fabricated in 3.95 to 8.2 GHz frequency range by embedding Frequency Selective Surface (FSS) between two Carbonyl Iron filled Silicon Rubber(CISR) sheets. CISR sheets have 24% and 33% concentration of carbonyl iron (CI) by volume. The frequency selective surface consist of three consecutive conductive square loops etched on 0.9 mm thick FR4 substrate. Broadband microwave absorber was tested by RDWG (Rectangular Dielectric Wave Guide) system and simulated by CST Microwave Studio. Simulated and measured return loss is better then -10 dB in 3.95 to 8.2 GHz in case of normal incidence. Simulated return loss for TM polarization is better then -10 dB for all angles of oblique incidence from 0° to 60°. Return loss is better then -10 dB for TE polarization, when angle of incidence is less then 15°.