YBCO MICROWAVE GRAIN-BOUNDARY MIXER USING A SRTIO3 BICRYSTAL SUBSTRATE

A microwave mixer was patterned on a microstrip transmission line of superconducting YBCO (YBa2Cu3O7-x). The YBCO film was epitaxially laser deposited on a SrTiO3 bicrystal substrate A weak link was constructed by patterning a microbridge in the microstrip at the bicrystal boundary. Two microwave signals were applied at the input of the microstrip line, one signal at 9.000 GHz and the other signal at 9.941 GHz An output intermediate frequency signal was observed at 941 MHz and was detected as the transmitted signal. The microbridge junction, which behaved as a resistively shunted Josephson junction (RSJ), was current biased slightly above the critical current I-c. The mixer conversion loss was measured at the input and output ports of the device package. With these measurements, the mixing efficiency was determined at the device junction, and this measured efficiency was compared with the calculated efficiency. The calculated efficiency was determined by numerical solution of the Josephson equation for the weak link junction.