Comparison of the different reconstruction techniques of permittivity from S-parameters

In this paper, we compare analytical and optimizing reconstruction methods for the electrical permittivity of materials. The reconstruction is done from the measured S-parameters of a coaxial transmission line. We compare the different reconstructions on materials of known electromagnetic properties, air, and ethanol. We conclude that two methods, one analytical (propagation matrices) and an optimization (L/sub 1/ norm), are the most appropriate for the reconstruction of permittivities, whether these are low-loss and constant over the frequency range or highly lossy and frequency dependent.