JOSEPHSON VOLTAGE STANDARD MICROWAVE CIRCUITS FABRICATED IN A MODIFIED ALL-NIOBIUM TECHNOLOGY FOR OPERATION AT LOW DRIVE FREQUENCIES

A resonant type of cryoelectronic microwave circuit for the generation of frequency-scaled Josephson voltages is presented. The circuits con sist of superconducting microstripline resonators with series arrays o f Josephson tunnel junctions located on the microwave current antinode s. This microwave design was chosen to obtain highly accurate Josephso n voltages at low microwave power levels and low drive frequencies. Th e resonator circuits have been fabricated in both niobium-lead and all -niobium technology. At present, we have observed long-term stable Jos ephson voltages up to 0.75 V for niobium-lead circuits with 1320 junct ions and 0.66 V for all-niobium circuits with 1456 junctions, respecti vely.