Reflection measurements of microwave absorbers

For certain applications the antenna designer may require a knowledge of the small scale, or localized, reflectivity properties of microwave absorbers. Suppliers of microwave absorbers generally quote the average absorption achieved over fairly large panels (610 × 610 mm) as determined by one of several free-space measurement techniques. By the nature of their construction, small samples of planar absorber panels cannot generally be evaluated directly in waveguide, particularly at X band and above. In this paper, we describe a swept-frequency, one-horn interferometer where the absorber panel is placed directly against the aperture of a well-matched horn.