OBLIQUE SCATTERING FROM LOSSY PERIODIC SURFACES WITH APPLICATION TO ANECHOIC CHAMBER ABSORBERS

Plane wave scattering from lossy, periodic surfaces with periodicity i n one direction is considered for arbitrary polarization and incidence angles. The material is assumed to be homogeneous, characterized by c omplex values of permittivity and permeability. Muller type coupled in tegral equations are derived for the surface electric and magnetic cur rents. Power reflection coefficient is defined in terms of the scatter ed far fields. The integral equations are solved by the boundary eleme nt method (BEM) with constant elements. Arbitrary surfaces are accomod ated by approximating the actual profile by means of linear segments. Other speed-up techniques are utilized to generate a numerically effic ient solution. Substantial comparison is made for special cases to ver ify the formulation. Reflection coefficient is calculated for a variet y of surface shapes such as rectangular, sinusoidal and triangular. A new profile shape is presented that results in a lower reflection coef ficient compared to the commonly used triangular shape. For the specif ic case of the triangular profile, a systematic study is carried out f or the dependence of reflection coefficient on various parameters.