Optimization of electromagnetic absorption in laminated composite plates

This paper analyzes an electromagnetic model of radar-absorbing layered structures for several stacking sequences of a woven glass/vinyl ester laminate, foam layers, and resistive sheets. It considers configurations that are either deposited on different backing materials or embedded in a laminated sandwich plate. Through-the-thickness layer dimensions and sheet resistances offering the best signal absorption over a specified frequency range are found for each configuration by minimizing an objective function with an enhanced genetic algorithm; The objective function includes selected values of minimum reflection coefficients and novel weight function distributions. In contrast to other optimization methods, this approach works with a population of initially selected values of the objective function and explores in parallel new areas in the search space, thus reducing the probability of being trapped in a local minimum. The procedure also yields the maximum reflection coefficient of -38.9 dB for a 01 incident wave passing through an optimized Jaumann absorber deposited on a metallic backing in the 7.5- to 18-GHz-range, which corresponds to 5.2 times smaller reflected signal than a patented design. Two additional surface-mounted designs and three sandwich, plate configurations are analyzed in a frequency, band used by marine radars. In general, the surface-mounted designs have much lower reflection coefficients.