High-Tc harmonic mixer applied to Josephson junction array voltage standard at NIM

A high-Tc superconducting (YBCO) Josephson-junction harmonic mixer has been used to improve the spectrum purity of the microwave source in the JJAVS at the National Institute of Metrology (NIM). Compared with the microwave source using source-locking counter EIP 578B, the spectrum purity of the microwave source has been improved significantly from -25 dBc/Hz (offset /spl plusmn/50 kHz) to -58 dBc/Hz (offset /spl plusmn/10 kHz). Therefore, the random uncertainty of the JJAVS was reduced.