Determination of complex permittivity for low- and high-loss materials at microwave frequencies

We present the determination of the complex permittivity for low loss PCB material FR4 and high loss arsenic-doped silicon wafer in the GHz frequency range, based on closed-form analytical expressions employing the Bessel´s functions. For convenience and economical reasons, the FR4 sample is cut from the commercial PCB as a sandwich disk of copper-dielectric-copper, while the bare silicon disk is contained in a prefabricated conducing cavity, referred to as the radial line cavity. Experimental measurements in support with the numerical analysis are also presented. Good agreement between computational results and laboratory measured data is observed.