A method using an open TEM cell to extract the complex permittivity of an unknown material

A simple method for the measurement of complex permittivity is presented using an open TEM (Transverse Electro-Magnetic) cell. The scattering parameters of the TEM cell are measured with and without a rectangular sample of the material under interest in the cross section of the cell. Then the principle is to run a FDTD (Finite Differences Time Domain) simulation of the measurement setup and find the complex permittivity of the sample model which minimizes the error between measurement and simulation thanks to an optimization loop. This method provides the complex permittivity of any non-metallic materials between 1 kHz and 200 MHz. The aim of this work is to make a fast parameter extraction to build a 3D simulation model and predict the shielding effectiveness of a complex geometry made of such a material.