Improvements in the millimeter-wave system for Josephson junction array voltage standard systems

Improvements in the millimeter-wave system have been made in order to generate higher and more accurate Josephson voltages directly. The 94-GHz oscillator operator output power has been increased to 90 mW by incorporating a novel InP Gunn diode, and a low-loss dielectric waveguide has been installed in liquid helium in order to increase the millimeter-wave power available at the input of the Josephson junction array chip. The stability of the millimeter-wave frequency has been improved to the order of 10/sup -11/. The losses of the waveguide-to-microstrip transition has been investigated but remain a matter for further improvement.<>