Electrically small resonator using thick-film high-T/sub c/ superconducting wire helix

A method for optimizing the geometry of half wave shielded helical resonators is presented, Copper and superconducting helical resonators, the latter made of YBCO thick film coated on zirconia wire, were designed and fabricated for tests. The resonant frequency could be predicted in relation to the helix and shield parameters. The surface resistance of YBCO was found at different frequencies and temperatures by the two-fluid model approximations and used to calculate the total loss resistance of the helix. The key parameters of the resonators were predicted, measured and compared. Good agreement was found for copper, but the unloaded Q of the superconducting resonator was lower than predicted, although this was expected, due to the polycrystalline nature of the superconductor.