| 摘要 |
A device that comprises an RF generator (29), an NMR transmission (20) and reception system (21) and a first control loop (28), with which the frequency fRF of the RF generator is synchronized with the resonance frequency f0 of an NMR line, wherein, from the signal of the RF generator, a train of excitation pulses (EX) of the repetition frequency fm is generated, with which nuclear spins of a certain resonance frequency of an associated NMR line are excited quasi-continuously (CW) and, in the times between the excitation pulses, the NMR signal is received (AQ), wherein the period time 1/fm is chosen to be much smaller than the relaxation time of the NMR line, preferably shorter than 1/10 of the relaxation time, and the NMR signal UD mixed down into the low-frequency range is used, with the help of the first control loop, to closed-loop-control the value of the transmission frequency (=frequency lock) or the value of the B0 field (=field lock) in such a way that the frequency and phase of the RF generator and the NMR line match as precisely as possible, characterized in that a phase shifter (22) that rotates the radio-frequency phase of the NMR transmission and reception system in the first control loop by the value &Dgr;&phgr; is controlled by a second control loop (27) whose input signal comes from a signal extraction stage (25, 26) that extracts the saw-tooth AC component of the signal UD and maintains this input signal at zero by closed-loop control. In this way, the influence of the RF phase on the synchronization process can be taken into consideration to improve the precision with which the resonance frequency of an NMR line is synchronized.
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