Programmable Josephson voltage standard (PJVS) circuits were developed that operate at 16 GHz to 20 GHz with operating margins larger than 1 mA. Two circuit designs were demonstrated each having a total of ~ 300,000 junctions, which were divided into either 16 or 32 sub-arrays. Triple stacked junctions were in order to fit the ~300,000 junctions of each circuit. The NbSix junction technology provided the high degree of uniformity of the barrier and the junction electrical properties, which was necessary to achieve the 1 mA operating margin. Although the margins on both the 16-array and 32-array circuits were much greater than 1 mA, the circuit yield for the 16-array design was lower because the longer arrays are more sensitive to defects. The use of lumped-element microwave splitters and tapered arrays significantly reduced the microwave input power and increased the operating margins of these designs. In addition, the broadband microwave response of the designs allowed the PJVS output voltage to be continuously adjusted using the microwave frequency while remaining on margins.
Citation: IEEE Transactions on Applied Superconductivity
Pub Type: Journals
Josephson arrays, SNS devices, superconducting device fabrication