New Evaluation Method of Dielectric Materials Using a Microwave Technique

A new nondestructive method of evaluating changes in characteristics or detecting internal defects in insulation materials with microwave techniques is discussed. The main feature of the method is that the amplitude and phase angle of a detected signal are displayed in a polar co-ordinate system, which allows changes in both the dielectric constant and loss tangent of a dielectric material to be obtained at the same time. The results of experiment on deterioration, the detection of foreign materials, and differences in the inner structure of complex insulation materials are shown.