A new technique to evaluate the complex permittivity of a homogeneous dielectric material using rectangular waveguide

This paper presents a simple waveguide measurement technique to evaluate the complex permittivity of a homogenous dielectric material. The dielectric sample is loaded in the transmission line rectangular waveguide WR90. The S-parameters of the waveguide are measured by Network analyzer and calculated as a function of the complex permittivity using theory of transmissions lines. Using the MatLab Optimization Tools simple MatLab scripts are written to search for complex permittivity of a dielectric material so as to match the measured and calculated values of S-parameters. The complex permittivity of Teflon and Nylon at the X-band frequencies are then determined.