Characterization of Antireflection Absorber Films Using WR-3.4 Waveguide Fixtures

Four different absorber films with thicknesses of less than 1 mm are characterized using waveguide sample holders in the 220-to-320 GHz range. The tested films consists of one multilayer type and three homogenous-material types. To obtain the material parameters for the films, high-frequency structure simulator simulations were employed, which were then compared with the measured two-port S-parameter data to determine the best fit. The results show one of the films with proper matching layer reduce the free-space reflectivity by more than 20 dB at 270 GHz. Additional tests in free-space environments demonstrate the effectiveness of the selected film in eliminating standing waves from metallic surfaces.