Study on the phase shifter in josephson junctions embedded microwave circuits

In a programmable Josephson voltage standard device which contains multiple branches of Josephson junction (JJ) array, the microwave reflection in arrays may result in a decrease in the Shapiro step margin. According to most of the previous designs, 90° phase shifter is used to cancel microwave reflection from branches to improve the performance of the device. This paper reports our study of the phase shifter in JJ array device with a 2-stage Wilkinson power divider. At first we designed and fabricated JJ array circuits with the phase shifters. Measurement results indicate that unequal powers have been reached to arrays. We then deleted the phase shifters in another design. Identical Shapiro step margins for 4 JJ array branches are achieved.