Josephson voltage standard at low drive frequencies

The authors report on the design and operation of a superconducting microstrip resonator containing four series-connected highly hysteretic Josephson junctions in the top layer. This arrangement generates constant-voltage steps at X-band drive frequencies useful for a Josephson voltage standard. At 12 GHz, steps up to 5 mV have been obtained with step amplitudes of about 100 mu A. The resonator principle can be used to save microwave power and to simplify the microwave circuit. To obtain sufficiently large and stable steps the critical current density and the junction length must be matched carefully with the order of maximum step used for the operation of the Josephson voltage standard. The X-band microwave drive frequencies offer substantial advantages in terms of costs and handling of microwave equipment.<>