Optimum Configuration of the Antenna to the Dielectric Resonator to Measure the Accurate Surface Resistance of the HTS Films

Abstract

The configuration of the antenna of the dielectric resonator is investigated to measure the exact surface resistance (R s ) of the high temperature superconductor (HTS) thin films over a wide range of temperature. The sapphire dielectric resonator is operated at 22GHz. The loop-terminated semi-rigid cables are used as the antennas. Using a Cu resonator at room temperature, the circumference length of the loop (L), the distance from the dielectric center to the loop center (d), and the height of the loop plane from the substrate surface (h) were changed. It is found that the smaller loop set at a position halfway to the height of the dielectric rod brought the widest region of d in which exact measurements can be carried out. This result was then applied using a HTS resonator. In order to measure exact Qu over a wide temperature region from low temperature to the critical temperature, weak coupling rather becomes a disadvantage. The best position of the antenna can be obtained when insertion loss set around -10dB at minimum temperature of the system.