Fabrication of Voltage Standard Circuits Utilizing a Serial–Parallel Power Divider

Digital-to-analog converter circuits utilizing NbTiN/Ti-TiN/NbTiN Josephson junctions were fabricated as quantum voltage standards, and were evaluated at around 10 K in a cryocooler. The first Shapiro step was generated at 2 V and had a height of more than 0.5 mA. Instead of a conventional microwave power divider that uses a quarter-wavelength resonator, a serial-parallel power divider was employed. This consisted of coplanar waveguides connected in parallel and coplanar strips connected in series. As a result, the chip area for the power divider was reduced by about 70%, and uniform frequency characteristics for the operating current margin were obtained.