A device for the highly precise synchronization of the nmr - transmission frequency to the resonance frequency of an nmr - line taking into account a hf - phase is not constant.

摘要

An apparatus which contains a hf - generator (29), an nmr - transmitter - (20) and reception system (21) as well as a first control loop (28), to which the frequency f_Rf of the hf - generator with the resonant frequency f.₀ a nmr - line is synchronized, wherein the signal of the hf - generator a sequence of excitation pulses (ex) of the repetition frequency f_m is generated, with the nuclear spins a specific resonant frequency of an associated nmr - line, so to speak, - continuously (cw) are excited and in the times between the excitation pulses - the nmr signal is received (aq), wherein the period 1 / f_m much smaller than the relaxation time of the nmr - line is selected, preferably shorter than 1 / 10 of the relaxation time, and that in the low frequency - region down mixed nmr - signal u_D for this purpose is used, with the aid of the first control circuit, the value of the transmission frequency (= frequency lock) or the value of the b₀-Field (= field lock) be controlled such that the frequency and phase of the hf - generator and the nmr - line coincide as precisely as possible, is characterized in that a phase shifter (22), the high frequency phase of the nmr - transmitter - and reception system in the first control circuit by the value δφ rotates, of a second control circuit (27) is controlled, the input signal from a signal extraction stage (25, 26), which to the sawtooth ac - proportion of the signal u_D this extracted and the input signal to zero. Thus, the influence of the hf - phase to the ..