Coplanar quarter-wavelength resonator filters fabricated by the superconducting sol-gel films
High temperature superconducting Y-Ba-Cu-O films were prepared on MgO polycrystal substrates by the sol-gel process. The average transition temperature and the surface resistance are 83 K and 2.8 m/spl Omega/ (at 30 K and 9.9 GHz, input power =-10 dBm), respectively. We fabricated a YBCO coplanar waveguide (CPW) quarter-wavelength (/spl lambda//4) resonator around 2 GHz (the length of the resonator is one half as long as that of the popular half-wavelength (/spl lambda/1/2) resonator) and compared its RF properties with that of a /spl lambda//2 resonator. Moreover, 2-pole CPW bandpass filter using YBCO sol-gel film was constructed with capacitively coupled /spl lambda//4 resonators. It has a narrow fractional bandwidth (3.60%) at 30 K.