Microwave-induced steps in Josephson junctions, DC-SQUIDs and parallel arrays

We have studied the characteristics of Shapiro steps in DC-SQUIDs and parallel Josephson junction arrays by means of numerical circuit simulation within the RCSJ model. Particular interest was dedicated to the occurence of fractional (subharmonic) steps, looking for possible relations to recent observations of this effect in high-TC junctions. Besides this, some new, pecliar effects in the dependence of step height vs. RF amplitude have been found, that correspond to characteristics measured on high-TC junctions and SQUIDs. The results can be useful for characterizing experimental Josephson junctions and circuits by studying dependencies of Shapiro steps.