Patent ID: 8456165

Claim:
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 RF phase, the device comprising: an RF generator having a frequency f RF ; an NMR transmission and reception system, said NMR transmission and reception system using an RF signal from said 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, wherein, in times between said excitation pulses, an NMR signal is received, a period time 1/f m being chosen to be much smaller than a relaxation time of the NMR line or to be shorter than 1/10 of said relaxation time; a first control loop, said first control loop synchronizing said frequency f RF of said RF generator with a resonance frequency f 0 of the NMR line, wherein said 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 0 field in such a way that a frequency and phase of said RF generator and the NMR line are matched; and a second control loop, said second control loop having a phase shifter that rotates a radio-frequency phase of said NMR transmission and reception system in said first control loop by a value Δφ, said phase shifter being controlled in said second control loop via an input signal produced by a signal extraction stage, said signal extraction stage extracting a saw-tooth AC component of the signal U D , wherein said second control loop maintains that input signal at zero via closed-loop control.