A new 10-V array of Josephson junctions based on low-frequency designs scaled up to 94 GHz

A novel approach is described for the design of improved coupling of millimeter-waves in a 10-V array of Josephson junctions. In this approach, microwave structures were fabricated and tested in the range 2.8 GHz to 3.6 GHz, and a scaling calculation was then used to transform them to 94 GHz. By optimizing the trade-off between antenna size and efficiency, it was possible to make more space available on the device chip to increase the number of Josephson junctions. Simulation results showed that the optimal antenna is a short double-fin-line type. This antenna type allowed us to fabricate a Josephson junction array that had 25944 Nb/Al-AlO_x/Nb junctions. For this new array, zero-crossing steps were observed up to 18.5 V. The new array was then successfully used to calibrate a Zener voltage standard that had a 10-V output