In-Situ Broadband Characterization of Complex Permittivity and Permeability of Magnetic Dispersive Materials

A coaxial-probe-based in-situ broadband measurement system has been established to characterize the complex Electromagnetic (EM) Parameters of magnetic absorbing materials. With an emphasis on key techniques for dispersive materials, the Frequency-variation method (FVM) was further studied for simultaneously measuring the both complex permittivity and complex permeability by intentionally varying the test frequency to obtain two different reflections. Criterions for a right order of the interpolation polynomial used to approximate the frequency-dependent EM parameters; measures to reduce the residual mismatch errors in reflection measurements and to suppress the ambiguities in solving the transcendent equation system were discussed in detail. Several typical dispersive absorbing coatings have been tested via FVM. The good comparison between the measured results and reference ones validate the feasibility of the proposed improved technique.