A 90 GHz band planar-type superconducting mixer using Ba1-xKxBiO3 (BKB
O) bicrystal junctions was fabricated on a MgO bicrystal substrate. Th
e mixer is integrated with microwave circuits and two junctions, but w
e could not operate the mixer in image rejection mode because of proce
ss damage to the junction properties. However we confirmed the mixing
operation; the intermediate frequency (IF) signal was observed up to 1
7K (LO = 87 GHz, RF = 92 GHz).