Analysis of Microwave Absorber Scattering Using Ray-tracing and Advanced Measurement Techniques

Ray-tracing methods can be applied to evaluate the wave propagation in anechoic electromagnetic environments, in order to improve measurement concepts, or to address the increasing demands on test concepts for new radio wireless transmission functionalities. The accuracy of the data obtained from such a chamber model depends crucially on the modeling of the microwave absorbers. Often the scattering off the absorbers is simplified by specular reflections, ignoring the actual direction-dependent scattering properties of the absorbers resulting from their geometry, arrangement, and material. As this may cause significant misconceptions, improved ray-tracing models of absorbers based on their scattering character are needed. In this paper, the scattering of two types of 18" absorbers with pyramidal and wedge geometries is analyzed and expected scattering patterns are described. Based on an existing shooting-and bouncing-rays software, a simulation approach is introduced and used to relate the analytical findings with results of measurements of the angle-dependent reflectivity. In addition to the primarily specular reflection for wedge absorbers and scattering in many directions off the pyramidal absorbers, the results show that nearfield effects influence this scattering pattern, as eventually confirmed by the simulations.