Design of compact multi-layer microwave absorber for ultra-wide band applications thru shaping and RAM technologies

Abstract

The present paper deals with improving the radar cross section reduction (RCSR) of a manufactured compact double-layer radar absorber material (RAM). The basic idea is to monitor the RCS performance of both operating frequency bands and electromagnetic wave (EMW) incidence angles by means of three altered structures. The interaction of EM fields with the three different structure geometries has been studied through the homogenization and/or forward-backward propagation approaches. Firstly, shaping a manufactured double-layer structure by way of uncoated periodic honeycomb is considered. Then, lonly a periodic coated honeycomb composite structure along with the expressions for its effective EM material properties are presented. Finally, multi-layered radar absorbing structure (RAS) has been studied through adding another planar thin RAM by using the extracted effective EM material properties of a periodic coated honeycomb composite structure. Genetic algorithm (GA) was applied in all RAS to optimize the thicknesses and/or material properties for better absorption of the incident EM wave. The effective material properties are measured through rectangular waveguide WR-90 and microstrip line fixtures. Comparing the results obtained from both measured and numerical solutions of the actual cross-sectional geometry, the engineered third planar layer is then manufactured to cover X, Ku and K bands up to 60̂ incident angles. The simulated results show that the designed structures an effective absorption values less than −10 dB on average in the desired bandwidths and angle of incidents for TE & TM modes. Bistatic experiment showed that the RCS values for the proposed RAS achieved more than −10 dB.