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TitleNon-linearity in Johnson noise thermometry
Publication TypeJournal Article
Year of Publication2012
AuthorsWhite, D.R.
Pagination651 - 665
Date Published2012
ISSN00261394 (ISSN)
KeywordsCorrelators, Direct measurement, Discrete tone, Field effect transistors, Inter-modulation products, Johnson noise thermometry, Junction field-effect transistors, Measurement time, Noise power, Noise thermometers, Quantum tunnelling, Spectral shapes, Temperature measurement, Test method, Third-order, Uncertainty analysis
AbstractThis paper discusses the effects of non-linearity, some of the mechanisms responsible for non-linearity, and methods for measuring non-linearity in Johnson noise thermometry. Mechanisms considered include quantum tunnelling, bipolar junction transistor and junction field-effect transistor amplifiers, feedback, clipping, output-stage crossover, quantization and dither. It is found that even- and odd-order effects behave differently in correlator-based noise thermometers, with the dominant even-order effects contributing as intermodulation products whereas the dominant odd-order contributions are third-order and at the same frequencies as the parent signals. Possible test methods include the use of discrete tones, changes in spectral shape, and direct measurement using reference noise powers. For correlators operated at constant noise power, direct measurement of non-linearity using reference noise powers enables corrections to be made with negligible additional uncertainty and measurement time. © 2012 BIPM & IOP Publishing Ltd.

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