Series arrays of 365 shunted YBa2Cu3O7−xJosephson junctions on yttria‐stabilized zirconia bicrystals were investigated under microwave irradiation in the K‐band. Sub‐arrays of up to 39 junctions were synchronized to the external microwave power at a temperature of 15 K. Although there was a considerable spread in the critical currents of the junctions and in the microwave bias current distribution, a first Shapiro step with a height of 30% of the total critical current of the sub‐array was obtained by using an external shunt resistor, thus reducing the spread in normal resistances to 5%. Such high‐Tccryoelectronic circuits are applicable for voltage standards and precision digital‐analog converters. ©1996 American Institute of Physics.