In this paper, an efficient lightweight double-layer microwave absorber with impedancematching structure at X-Ku bands was designed, optimized and implemented. First, genetic algorithm (GA) was considered to optimize the thicknesses and material properties for better absorption of the incident electromagnetic wave and reduction of radar cross section (RCS). Next, with the aid of the obtained dielectric and magnetic properties, the microwave absorber was fabricated from magnetodielectric composite materials besides a natural rubber. Finally, the analytical and numerical results were compared with the measurements to check the validity of the design. Experiments showed that the reflection coefficient for each layer backed with a metallic sheet was insufficient; however, for the double layer absorber, the reflectivity measurement values reached up to −28 dB in the case of normal incidence and −17 dB for oblique incidence.

In this paper, straightforward and efficient techniques have been addressed into double-layer structure to enlarge the operating bandwidth to include the X, Ku and K bands, in addition to increase the electromagnetic wave absorption for wide varieties of incident angles and both polarization types. To increase the band-stop resonating frequency up to 26 GHz, an additional layer of meta-surface, circuit analog radar absorber material (CAR), or a thin radar absorber material (RAM) layer is engineered. The synthesized layers are designed based on optimization process with genetic algorithm (GA) through numerical technique (Ansoft design software HFSS) for both transmission line (T.L) and the free space method to get optimal material properties suitable for the design. For different approaches, the designed structures achieved a reflectivity value less than −16 dB on average in the desired bandwidth from 8 to 26 GHz for TE/TM modes with incidence angle up to 50̂.

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, multilayered 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 60 • 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.