Dielectric Characterization of RF-Printed Circuit Board Materials by Microstrip Transmission Lines and Conductor-Backed Coplanar Waveguides Up to 110 GHz

This paper introduces a method for determining the attenuation constant and the dielectric permittivity (Dk) by microstrip lines and/or conductor-backed coplanar waveguides. The method considers several effects (surface waves, frequency-dependent conductance, inductance, and resistance) for obtaining the attenuation constant of the line and the Dk of the substrate out of measurements. For the compensation of conductor properties, an easily applicable formula for any low loss transmission line is derived that avoids extensive simulations. The validity of the method is shown by measurements of two RF-substrate materials up to 110 GHz. The resulting Dk not only shows excellent agreement with available data sheet values, but also extends the investigated frequency range.