A generic approach for permittivity measurement of dielectric materials using a discontinuity in a rectangular waveguide or a microstrip line

A generic approach is proposed to accurately measure microwave and millimeter-wave properties of dielectric materials. This novel technique first determines the scattering parameters of a discontinuity containing a material having a wide range of complex dielectric permittivity ε that is known a priori (the direct problem). The discontinuity is embedded in a rectangular waveguide or a microstrip line. A unified theory, which is essentially based on a combination of the boundary integral equation technique with a modal expansion approach, is presented to tackle the direct problem. A class of generic diagrams are obtained for interrelating the dielectric permittivity ε to its S-parameters, and a simple analytical expression is deduced to solve the inverse problem. The proposed analytical formulation is easy to use and much more rapid than its iterative counterparts. It demonstrates a completely new and efficient strategy for accurate complex dielectric measurements