Frequency Domain Measurements of Microwave Absorber Design Materials

摘要

Using frequency domain techniques, a system was developed to measure the complex permittivity and permeability of different materials in the Ku band (12.4 to 18 GHz). A sample of fiberglass, teflon, FGM-40, and two different plexiglas configurations were chosen for this experiment. The newly developed measuring system consisted of a two horizontal-plane sectoral horn and a sample holder assembly. A 9.5 x 0.8 cm piece of the sample material was cut and fitted into the sample holder assembly. The reflection and transmission coefficients for the sample were measured, using a network analyzer and frequency synthesizer as the swept frequency signal source. A dedicated computer calculated the complex permittivity and permeability and plotted the output data. The two configurations of plexiglas and the fiberglass sample were tested ten times to obtain a statistical representation of the results. The permittivity and permeability obtained for the selected samples using the frequency domain measurement technique were compared with the results obtained in a previously developed system which used time domain techniques. The data comparison between the two systems was good for teflon, plexiglas, and fiberglass in the frequency range from 12.4 to 16 GHz. Some variations were noted for the FGM-40. Since the results obtained were generally consistent between both techniques, it is claimed that the newly implemented frequency domain system is a viable alternative for the rapid measurement of intrinsic properties in the Ku band.