A Method for the Measurement of RF Absorber using Spectral Domain Transformations

Indoor antenna ranges must have the walls, floor and ceiling treated with RF absorber. Pyramidal absorber is shaped to create an impedance transform from free space to that of the absorbing material. The pyramidal shape provides this very effectively for normal incidence, but performance typically gets worse as the angle of incidence deviates from normal. Unfortunately, it is difficult to measure reflectivity at large oblique angles because of difficulty differentiating the reflected signal from that of the direct path. In this paper, a novel approach for performing such measurements is introduced. Preliminary measurements are compared to RF simulations. The comparison appears to indicate that this approach is a valid way to perform RF absorber measurements at wide angles.