Coplanar quarter-wavelength resonator filters fabricated by the superconducting sol-gel films

High temperature superconducting Y-Ba-Cu-O films were prepared on MgO polyc rystal substrates by the sol-gel process. The average transition temperatur e and the surface resistance are 83K and 2.8m Omega (at 30 K and 9.9GHz, in put power = -10dBm), respectively. We fabricated a YBCO coplanar waveguide (CPW) quarter-wavelength (lambda/4) resonator around 2GHz (the length of th e resonator is one half as long as that of the popular half-wavelength (lam bda/2) resonator) and compared its RF properties with that of a lambda/2 re sonator. Moreover, 2-pole CPW bandpass filter using YBCO sol-gel film was c onstructed with capacitively coupled lambda/4 resonators. It has a narrow f ractional bandwidth (3.60%) at 30K.