RF applications of high temperature superconductors in MHz range

High quality, low noise RF devices (resonators and filters) in MHz range have been designed, fabricated, and tested. The devices were designed using either interdigital capacitor or spiral structures and made from two inch HTS wafers. Applications of these devices to magnetic resonance imaging (MRI) and RF communication are reviewed. Substantial gain in signal-to-noise ratio (SNR) using HTS coils for both proton and sodium MRI on animals and humans at field strength of 0.5 T-3 T are demonstrated. HTS single-pole and three-pole bandpass filters operated at 77 K are built. Multi-pole bandpass filters in MHz range are successfully made on two-inch, single layer HTS wafer. A three-pole filter with a center frequency of 18 MHz has shown a low insertion loss of 0.7 dB at 77 K.