Electromagnetic Scattering from a Structured Slab Comprised of Periodically Placed Resistive Cards

摘要

The structured slab, which is constructed by arranging cells composed of thin, lossy, dielectric cards on a one- or two-dimensional lattice, is an important material in the aerospace industry because of its high strength-to-weight ratio. Recently, the structured slab has also been used to reduce the radar cross section of various aircraft. It is important, therefore, to characterize how an electromagnetic wave scatters from this slab. The structured slabs discussed in this report are constructed by repeating lossy strips periodically in one dimension or lossy plates in two dimensions. An electric field integral equation is formulated which has as its unknown the electric current flowing in a single unit cell of the structure. The periodicity of the structure is accounted for by using an efficiently calculated periodic Green's function. The loss is modeled by resistive boundary condition. The integral equation is solved by the method of moments using subdomain basis functions. The generalized scattering matrix is calculated and the propagating reflection coefficients are plotted as a function of frequency for various structures. The oblique scattering from one-dimensional arrays of strips is examined for various configurations of unit cells and various resistances. A depolarizing effect of the structure is found to be a function of incident angle and symmetry in the unit cell. The reflection from two-dimensional arrays of plates connected to form slabs of zigzag plates and honeycombs is also examined. The symmetry of the honeycomb unit cell minimizes the coupling between the TE and TM polarizations. (RH)