W-band measurements of low-loss dielectrics with a Fabry-Perot Open Resonator

Complex permittivity of selected low-loss materials, such as monocrystalline quartz, polypropylene-silicon, teflon and a few ceramic compositions, are measured with a Fabry-Perot open resonator with Gaussian concave mirrors operating in a W-band (75-100 GHz). The measurement algorithm is based on a recently introduced electromagnetic model of that kind of a resonator, which takes the advantage of conformal transformation of Maxwell curl equations from Cartesian to Gaussian coordinate system. That concept has been confirmed experimentally in the 20-50 GHz with a vector network analyzer directly connected to the resonator. In this paper, the measurement setup is additionally equipped with 75-110 GHz frequency extenders terminated with WR-10 waveguides, while the rest of the system and of the measurement algorithm is very much the same as in 20-50 GHz.