JPH079112Y2 - Nuclear magnetic resonance apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention is a nuclear magnetic resonance apparatus (NMR apparatus) equipped with a phase variable oscillator capable of changing the phase of an output signal by an arbitrary amount at an extremely fast response speed. It is about.

[Prior Art] In the NMR apparatus, a magnetic field lock device is provided to keep the static magnetic field strength constant. This magnetic field lock device constantly monitors, for example, a resonance signal (dispersed waveform) of deuterium nuclei mixed in a measurement sample with a lock transmission / reception system provided separately from the measurement system, and based on the resonance signal, a static magnetic field It controls the strength. In this magnetic field lock device, irradiation of deuterium nuclei with a high frequency for locking and reception of a resonance signal are alternately performed at an appropriate cycle. At that time, the resonance signal is used for demodulation so that the resonance signal has an accurate dispersed waveform. It is necessary to finely adjust the phase with respect to the high frequency irradiated on the high frequency deuterium nuclei. Therefore, conventionally, for example, as shown in FIG. 4, a circuit composed of a high-frequency oscillator OSC and a phase shifter PS is used.
The high frequency for irradiation is taken out from the gate G1, and the high frequency for demodulation is taken out from the gate G2.

[Problems to be Solved by the Invention] In such a conventional example, an analog circuit including a capacitor and a resistor is used as a phase shifter, and the operator adjusts the analog circuit. There are drawbacks such as difficulty, poor reproducibility, and difficulty in control by computer.

[Means for Solving the Problems] The present invention has been made in view of the above-described points, and does not attach an analog phase shift circuit to an oscillator, but outputs a signal of an arbitrary phase in a time division manner. It is an object of the present invention to provide an NMR apparatus equipped with an oscillator capable of generating a magnetic field.

The NMR apparatus of the present invention has a memory storing a large number of digital values forming a sine waveform, a means for repeatedly generating a digital sweep signal, the digital sweep signal being supplied to one input terminal, and the output thereof being An adder that is supplied to the memory as an address signal for reading from the memory, a phase value generator that supplies a digital value representing a phase to the adder in a time division manner, and an output signal of the adder are provided. By converting the digital value read from the memory as an address signal into an analog signal in a time division manner in synchronization with the time division by the phase value generating means, two kinds of analog signals corresponding to two kinds of phase values can be obtained. Means for obtaining in a time division manner, lock transmitting / receiving coil to which one of the two kinds of analog signals obtained in a time division manner is supplied, and the transmitting / receiving coil for lock And a resonance signal obtained from the demodulator for resonance signal demodulation to which the detection signal obtained from the above is supplied and the other of the two types of analog signals obtained in the time division manner is supplied as a reference signal. And a magnetic field control means for controlling the static magnetic field intensity based on the signal. Hereinafter, the present invention will be described in detail with reference to the drawings.

[Embodiment] FIG. 1 is a block diagram showing an embodiment of the present invention, in which 1 is a magnet for generating a static magnetic field, 2 is a correction coil for varying the magnetic field strength, and 3 is a transmitter / receiver for observation. coil,
Reference numeral 4 is a transmitting / receiving coil for locking. Reference numeral 5 is an oscillator that generates two high frequency waves having the same frequency but different phases in a time division manner. Each high frequency wave was mixed with another high frequency wave in the mixers 6 and 7, and the frequency was raised to the resonance frequency of the deuterium nucleus. After that, one is sent to the transmission / reception coil 4 via the gate 8 and the other is supplied as a reference signal to the demodulator 10 described later via the gate 9. The resonance signal induced in the transmission / reception coil 4 is taken out through the gate 11 and sent to the demodulator 10 for demodulation. The magnetic field control circuit 12 controls the magnetic field strength based on the resonance signal obtained by demodulation and locks the magnetic field.

In the above-described configuration, the oscillator 5 includes, for example, a memory (ROM) 13 in which data values regarding a sine waveform for one cycle are stored, a clock oscillator 14, and a sweep circuit 15 that generates a digital sweep signal based on the clock signal. , A time division circuit 16 for controlling the timing of time division based on a clock signal, a variable digital value generation circuit 17, an addition circuit 18, a gate
19. It comprises two DA converters 20 and 21 to which the digital value read from the ROM 13 is supplied, and low pass filters 22 and 23.

FIG. 2 (a) shows the input / output characteristics of the ROM 13, where the horizontal axis is the address and the vertical axis is the output digital value. Second
As can be seen from the figure (a), the sine waveform for one cycle is divided into, for example, 2,000 points of data, and for example, the address is designated as 0 → 1 → 2 → 3 → ... Every 1 μsec. If all data are sequentially read by, one cycle 2000 μsec (500 Hz)
The staircase signal of is obtained as the output of the DA converter. If data is skipped and read every 100 microseconds by designating the address as 0 → 100 → 200 → 300 → ... every 1 microsecond, one cycle is 20 microseconds (50KHz) as shown in Fig. 2 (b).
The staircase signal of is obtained, and if data is read every 500 pieces as shown in FIG. 2 (c), one cycle is 4 μsec (250 KH
The waveform of z) can be obtained. In this way, it is possible to extract a signal of an arbitrary frequency by changing the number of skipped and read data.

The sweep circuit 15 reads 0 when data is read every N pieces.
→ 2N → 3N → ・ ・ ・ → 0 → N → 2N → ・ ・ ・ Generates a digital sweep signal and uses this as an address signal to adder circuit 18
To ROM13 via. At this time, in the present invention, the addition circuit 18 is configured to add an arbitrary digital value M generated by the variable digital value generation circuit 17 to the address signal from the sweep circuit. Now, if the value of M is 10 and the address signal generated from the sweep circuit 15 is swept as 0 → 100 → 200 → 300 → ... When N = 100, the output of the adder circuit 18 is 10 → 110 → 210 → 310 → ・ ・
The signal read from the ROM 13 by this address signal is as shown in FIG. 2 (b) as shown in FIG. 2 (d).
Although the waveform is slightly different from that of the signal, the signal has the same cycle of 200 μsec (frequency of 50 KHz) and is delayed by 10 data in phase. In this case, the phase delay φ is (M / N) × 360 °
= 36 °, and if M is changed by 1, the phase can be changed in 3.6 ° steps.

Similarly, if N = 500, the phase can be changed in 360 ° / 500 = 0.72 ° steps by changing M by one.

3A and 3B show control signals a and b generated by the time division circuit 16, respectively. The two control signals are given appropriate time division frequencies, and their phases are inverted as can be seen from the figure. Since the gate 19 is turned on and off based on the control signal b as shown in FIG. 3 (c), the value of M sent to the adder circuit 18 through the gate 19 is "0" when the gate is off. ", ON
At that time, it becomes "M". The operations of the D-A converters 20 and 21 are turned on and off by the control signals a and b, respectively, as shown in FIGS. 3D and 3E, so that the D-A converter 20 is ON. , The signal f1 (o) having a phase of zero is taken out from the D / A converter 20, and the signal f1 having a phase of φ is output from the D / A converter 21 while the D / A converter 21 is ON. φ) will be taken out.

In this way, f1 (o) and f1 (φ) are taken out alternately.
Are mixed with a signal f2 having an appropriate frequency in mixers 6 and 7, and output as a signal f3 having a resonance frequency of deuterium nuclei, respectively.
(O) and f3 (φ) are taken out. Among them, f3 (o) is D
It is sent to the transmission / reception coil 4 through the gate 8 which is turned on / off in synchronization with the -A converter 20, and is irradiated to the deuterium nuclei in the sample, while f3 (φ) is transferred to the DA converter 21. ON-OF synchronously
The signal is sent to the demodulator 10 via the gate 9 which is turned on. Therefore, irradiation of deuterium with f3 (o) and demodulation based on f3 (φ) of the resonance signal induced in the transmission / reception coil 4 due to the irradiation are alternately performed in a time division manner. Become.
Then, the magnetic field controller 12 controls the magnetic field strength by controlling the current supplied to the correction coil 2 based on the resonance signal (dispersion waveform) obtained by demodulation, and locks the magnetic field. It goes without saying that the output M of the variable digital value generation circuit 17 may be adjusted as described above in order to adjust the phase shift amount φ.

[Effect of the Invention] As described in detail above, according to the present invention, unlike the conventional case in which an analog phase shift circuit including a capacitor and a resistor is used,
Since an NMR device equipped with an oscillator that can selectively and selectively generate a signal with an arbitrary phase is realized, it is possible to perform accurate phase matching, good reproducibility, and high-speed computer control. There are some effects.

Further, since one ROM 13 can obtain signals of two phases in a time division manner, there is an effect that the configuration is not complicated.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a waveform diagram for explaining the frequency variable and phase variable operation of the oscillator 5, and FIG. 3 is an operation of the apparatus of FIG. FIG. 4 is a timing diagram for doing so, and FIG. 4 is a diagram for explaining a combination of a conventional oscillator and a phase shifter. 1: Magnet, 2: Correction coil, 3: Observation transmission / reception coil, 4: Lock transmission / reception coil, 5: Oscillator, 6,7: Mixer, 8,9,11,19:
Gate, 12: Magnetic field control circuit, 13: ROM, 14: Clock oscillator, 15: Sweep circuit, 16: Time division circuit, 17: Variable digital value generation circuit, 18: Addition circuit, 20, 21: DA converter , 22,23: Low-pass filter.

Claims (1)

[Scope of utility model registration request] 1. A memory storing a large number of digital values forming a sine waveform, a means for repeatedly generating a digital sweep signal, the digital sweep signal being supplied to one input terminal, and the output thereof being the memory. From the adder means as an address signal for reading from the memory, phase value generating means for time-divisionally supplying a digital value representing a phase to the adder means, and an output signal of the adder means being an address signal. As the digital value read from the memory, the two kinds of analog signals corresponding to the two kinds of phase values are time-divided by time-divisionally converting into analog signals in synchronization with the time division by the phase value generating means. Means, a lock transmitter / receiver coil to which one of the two types of analog signals obtained in a time division manner is supplied, and a lock transmitter / receiver coil. To the resonance signal obtained from the demodulator for resonance signal demodulation to which the other of the two types of analog signals obtained in a time division manner is supplied as a reference signal while the detected signal is supplied. And a magnetic field control means for controlling the static magnetic field intensity based on the nuclear magnetic resonance apparatus.