The ac Josephson effect in hysteretic junctions: Range and stability of phase lock

The rf-induced constant voltage steps generated by the ac Josephson effect are studied within the context of the Stewart-McCumber model. Simulations are used to determine the range of current bias over which phase lock occurs for model parameters appropriate to hysteretic tunnel junctions. The effect of noise on phase lock is also considered. The results are applied to a zero-bias voltage standard proposed by Levinsen et al.