Numerical phase locked loop for nuclear oscillators oscillation frequency automatic control in parasitic rays and NMR tests

摘要

The oscillator (100) is optimised by measuring the ambient magnetic field intensity, using a NMR probe (2). Its output signal is applied to a phase locked loop (4), generating numerically a first sinusoidal sample and a second sample to excite the probe, after treatment (48, 5). At least one amplitude (A, B) or phase (p) sample generated by the loop is modified. The first signal (A) amplitude may be modified or cancelled out, modifying the band pass of the oscillator, or de-activating the phase locked loop. Alternatively, the second signal amplitude or phase may be modified, altering the probe excitation, or its phase. Samples generated by the loop may be stored in first (45) and second (47) memories, added to predetermined parameters, to operate on addresses, controlled by microprocessor (20).