Automated dielectric constant and loss tangent characterization using cavity resonators

A simple method for dielectric constant characterization is the full sheet resonance method. In this technique, the dielectric constant is extracted from the resonance frequencies of a parallel-plate waveguide resonator. The standard method cannot be applied to extract the loss tangent. Recently, the full-sheet resonance method has been extended to extract the loss tangent as well. The new method makes use of a new rapid plane solver and resonators with shorted boundaries. The materials properties are extracted by fitting the simulations to measurements. In this paper, we will demonstrate how the fitting process can be automated. In order to extract the dielectric constant and loss tangent, many simulations need to be run to find the parameters that provide the best match with the measurements. This is a computationally expensive approach. We will present a new method based on tracking sensitivity, which provides a parameterized macromodel for the resonators. Using this approach, the simulation data can be expressed as a low-order rational function of the complex permittivity. Hence, varying the complex permittivity to find the best fit can be done in negligible time after the macromodel has been generated. This new method will be applied to extract the dielectric constant and loss tangent of FR-4.