Device for extremely precise synchronisation of NMR transmission frequency to the resonance frequency of an NMR line taking into consideration a non-constant HF phase

摘要

A device for highly precise synchronization of an NMR transmission frequency to a resonance frequency of an NMR line, comprises an radio frequency (RF) generator (29) having a frequency (f r f); an NMR transmission (20) and reception system (21), where the NMR transmission and reception system using an RF signal from the generator to produce a train of excitation pulses; a first control loop (28), where the first control loop synchronizing the frequency (f r f) of the RF; and a second control loop (27), where the second control loop having a phase shifter that rotates a radio-frequency. A device for highly precise synchronization of an NMR transmission frequency to a resonance frequency of an NMR line while taking into consideration a non-constant radio frequency (RF) phase, comprises an RF generator (29) having a frequency (f r f); an NMR transmission (20) and reception system (21), where the NMR transmission and reception system using an RF signal from the generator to produce a train of excitation pulses having a repetition frequency (f m) with which nuclear spins of a certain resonance frequency of an associated NMR line are excited quasi-continuously, where, in times between the excitation pulses, an NMR signal is received, a period time 1/f mis chosen to be much smaller than a relaxation time of the NMR line or to be shorter than 1/10 of the relaxation time; a first control loop (28), where the first control loop synchronizing the frequency (f r f) of the RF generator with a resonance frequency (f 0) of the NMR line, where the first control loop utilizes an NMR signal (U d) mixed down into a low-frequency range to closed-loop-control and frequency lock a value of transmission frequency or to field lock a value of the B 0field in such a way that a frequency and phase of the RF generator and the NMR line are matched; and a second control loop (27), where the second control loop having a phase shifter that rotates a radio-frequency phase of the NMR transmission and reception system in the first control loop by a value delta phi , where the phase shifter being controlled in the second control loop via an input signal produced by a signal extraction stage, the signal extraction stage extracting a saw-tooth AC component of the signal (U d), where the second control loop maintains that input signal at zero via closed-loop control. An independent claim is for synchronization system having a first and second device comprises the elements recited in the device, where an NMR measurement sample is used with at least two NMR lines with resonance frequencies f 0 1and f 0 2and with different temperature coefficients, where the first device is synchronized selectively to f 0 1and the second device selectively to f 0 2, where a differential frequency (f 0 2-f 0 1) is measured to determine a temperature value of the NMR measurement sample and to designate it as the temperature value of an NMR thermometer.