Automatic NMR field-frequency lock-pulsed phase locked loop approach.
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.
Kan
S
S
Institut d'Electronique Fondamentale, Laboratoire associe au CNRS, Universite Paris-Sud, 91405 Orsay, FranceLaboratoire de Chimie Organique Structurale, Universite Paris Sud, 91405 Orsay, France.
Gonord
P
P
Fan
M
M
Sauzade
M
M
Courtieu
J
J