Broadband Josephson Voltage Standards

Published

May 20, 2001

Author(s)

Clark A. Hamilton, Samuel P. Benz

Abstract

A Josephson junction is a perfect frequency to voltage converter, that is, V=f/K_j where K_j = 483597.9 GHz/V. This unique property has been used to convert a narrow (1 Hz) band 75 GHz reference frequency to a dc voltage standard. Josephson standards use arrays of thousands of junctions to raise the voltage to 10 V. During the last 30 years metrologists have reduced the uncertainty in dc voltage among national measurement institutes by 3 orders of magnitude to a level of about 1 part in 100. More recently, the broadband capability of Josephson devices is being exploited at NIST to create a new ac voltage standard. In this case, the Josephson junction is modeled as a pulse generator that can be triggered at frequencies fro dc to 30 GHz, and that produces short (~50 ps) voltage pulses with a time integral of exactly 1/K_j. A delta-sigma algorithm with a high oversampling ratio is used to define a digital pulse sequence for any desired output waveform. The sequence is programmed into a digital code generator that triggers the Josephson device. The result is a replication of the desired waveform with a time-dependent amplitude that is exactly calculabel from a knowledge of the pulse code, the sampling frequency, and the number of Josephson junctions in the array. The talk will summarize progress to date on this new ac voltage standard.

Proceedings Title

Tech. Dig., IEEE MTT-S International Microwave Symposium

Volume

2

Conference Dates

May 20-25, 2001

Conference Location

Phoenix, AZ

Conference Title

IEEE MTT-S International Microwave Symposium

Pub Type

Conferences

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Keywords

broadband, digital-to-analog converter, frequency, Josephson junction, quantization, voltage standard

Citation

Hamilton, C. and Benz, S. (2001), Broadband Josephson Voltage Standards, Tech. Dig., IEEE MTT-S International Microwave Symposium, Phoenix, AZ, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=30216 (Accessed April 20, 2024)