Wideband relative permittivity extraction based on CPW phase constant measurements

We introduce a semi-numerical method to extract the relative permittivity of typical microwave substrate materials from on-wafer scattering-parameter measurements of coplanar waveguides of different lengths. Despite its numerical nature, the method is robust and converges rapidly. We demonstrate the accuracy of the method using structures built on four different substrates in a frequency range up to 110 GHz.