Complex permittivity measurements at variable temperatures of low loss dielectric substrates employing split post and single post dielectric resonators

A split post dielectric resonator in a copper enclosure and a single post dielectric resonator in a cavity with superconducting end-plates have been constructed and used for the complex permittivity measurements of single crystal substrates. (La,Sr)(Al,Ta)O₃, LaAlO₃, MgO and quartz substrates have been measured at temperatures from 20 K to 300 K in the split post resonator and from 15 K to 80 K in the single post resonator. The TE_01δ mode resonant frequencies and unloaded Q₀-factors of the empty resonators at temperature of 20 K were: 9.952 GHz and 25,000 for the split post resonator and 10.808 GHz and 240,000 for the single post resonator respectively.