JOSEPHSON VOLTAGE STANDARD - A REVIEW

The unique ability of a Josephson junction to convert a microwave freq uency f into a voltage Nhf/2e with high accuracy and the adoption of t his phenomenon as the basis for the SI Volt Realization have created a market for Josephson voltage standards that is unassailable from any other technology. This paper reviews the development of Josephson volt age standards including the junction and array design, the microwave c ircuit, and the system integration, With the dr Josephson standard lar gely transferred to the commercial sector, NIST is developing a new cl ass of devices in which the output voltage can be rapidly programmed e ither by digitally selecting the quantum number N or by driving tile J osephson array with a variable frequency pulse train. These new device s will make possible fret, high-accuracy characterizations of A/D and D/A converters and the synthesis of ac waveforms.