Automatic NMR field-frequency lock—pulsed phase locked loop approach
- 1 June 1978
- journal article
- Published by AIP Publishing in Review of Scientific Instruments
- Vol. 49 (6) , 785-789
- https://doi.org/10.1063/1.1135615
Abstract
A self-contained deuterium frequency-field lock scheme for a high-resolution NMR spectrometer is described. It is based on phase locked loop techniques in which the free induction decay signal behaves as a voltage-controlled oscillator. By pulsing the spins at an offset frequency of a few hundred hertz and using a digital phase-frequency discriminator this method not only eliminates the usual phase, rf power, offset adjustments needed in conventional lock systems but also possesses the automatic pull-in characteristics that dispense with the use of field sweeps to locate the NMR line prior to closure of the lock loop.Keywords
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