Reflection of plane waves from absorber pyramids: transmission line matrix analysis

A numerical method that can be used to analyze an infinite array of pyramid absorbers such as those used in anechoic chambers excited by a plane wave of arbitrary frequency and angle of incidence is presented. The method can be adapted to any absorber geometry. The problem is solved using transmission line matrix (TLM) analysis over a mesh placed around one absorber pyramid. Link voltages exciting the side of the single cell are delayed by a phase factor dependent on the frequency and angle of incidence and reinserted into the opposite side. This effectively simulates an infinite array of such absorbers. The method works because of the fact that the exciting signal looks the same everywhere (except for phase). The method yields gross reflection coefficient as a function of frequency and angle of incidence for any given absorber shape