Accurate Measurements of Permittivity and Dielectric Loss Tangent of Low Loss Dielectrics at Frequency Range 100 MHz - 20 GHz

This paper describes the state-of-the-art of measurements frequency range for low loss low permittivity materials at frequency range from 100 MHz to 20 GHz and includes new developments in the reentrant cavity technique. In particular it is shown that geometric factor values for reentrant cavity with sample under test basically depends on the resonant frequency of the cavity containing the sample, with negligible variations versus sample size and its permittivity. Measurements on PTFE versus frequency have shown that for this material both real part of permittivity and dielectric loss tangent are practically constant in frequency range of 100 MHz-20 GHz.