JOSEPHSON VOLTAGE STANDARD MICROWAVE CIRCUIT DRIVEN AT 10 GHZ

We have investigated a new type of microwave circuit for the generatio n of frequency-scaled Josephson voltages useful for the representation of highly accurate reference voltages. The circuit consists of a supe rconducting microstrip resonator and series arrays of Josephson juncti ons integrated within its rf current antinodes. The circuit is designe d to operate at low frequencies of about 10 GHz to simplify the microw ave techniques. At a resonator circuit with four Josephson junctions d riven at 10.9 GHz we have obtained stable overlapping Shapiro steps up to 4.6 mV at a step width of about 70 muA. A more advanced double-res onator circuit with altogether 216 junctions allows to generate scaled reference voltages up to 0.16 V at steps of about 25 muA in width and at a microwave frequency of 11.1 GHz.