Measurement of the Intrinsic Properties of Materials by Time-Domain Techniques

In this paper a method is presented for determining the complex permittivity and permeability of linear materials in the frequency domain by a single time-domain measurement; typically, the frequency band extends from VHF through X band. The technique described involves placing an unknown sample in a microwave TEM-mode fixture and exciting the sample with a subnanosecond baseband pulse. The fixture is used to facilitate the measurement of the forward- and back-scattered energy, s21(t) and s11(t), respectively. It is shown in this paper that the forward- and back-scattered time-domain "signatures" are uniquely related to the intrinsic properties of the materials, namely, ϵ* and μ*. By appropriately interpreting s21(t) and s11(t), one is able to determine the real and imaginary parts of ϵ and μ as a function of frequency. Experimental results are presented describing several familiar materials.