Automated complex permittivity characterization of ceramic substrates considering surface-roughness loss

This paper presents a new method to extract the frequency-dependent dielectric constant and loss tangent of ceramic substrates from high frequency measurements of cavity resonators. A cavity resonator can be realized using two ground planes connected with vias to form the side walls. Recently, a rapid plane solver has been developed to efficiently and accurately simulate cavity resonators and extract materials properties by manually fitting simulations to measurements. In this paper, we 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 a ceramic substrate in the presence of surface roughness loss. © 2012 International Microelectronics And Packaging Society.