JPS62198741A - Automatic phase correction system for nuclear magnetic resonance system - Google Patents

Abstract

PURPOSE:To correct a phase automatically by making the phase correction by using a current extremely short timing time even during the input of a nuclear magnetic resonance (NMR) signal. CONSTITUTION:A high frequency output for NMR excitation which is generated by a frequency mixer 27 is applied to the detection coil of an NMR detector 1 through an NMR signal exciting amplifier 30, etc. An NMR signal detected by the detector 1 is divided into two through a high frequency amplifier 6, etc., and lead to phase detectors 7 and 8. The detectors 7 and 8 are applied with frequency signals for detection which are 90 deg. out of phase with each other from a phase controller 22 and the divided signals are mixed with those frequencies, so that 90 deg.-out-of-phase NMR signals are outputted. Extremely short timing in NMR signal detection is used to switch gate circuits G1-G9 and the 90 deg.-out- of-phase outputs of the detectors 7 and 8 are supplied to an arithmetic circuit 20 for phase error calculation through amplifiers 14 and 15 for phase error detection; and the circuit 20 generates a phase control feedback signal based upon the phase error and applies it to a phase control circuit 24 to make the automatic phase correction.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is a core that can correct phase changes on the excitation high frequency generation side and phase changes in the actual setting of the detection and amplification system including the probe. This invention relates to an automatic phase correction method in a magnetic resonance apparatus.

[Conventional technology]

NMR (Nuclear Magnetic Resonance) spectrum is usually a phase spectrum, and if there is a phase lead or lag in the circuit from the signal detection probe to the amplifier and even the AD (Analog/Digital) converter, the phase of the signal will change. For example, in a circuit from the excitation to the detection system of an NMR (nuclear magnetic resonance apparatus), when the temperature changes, a phase shift occurs due to a change in electrical constants.

When such a phase shift occurs, it becomes impossible to distinguish whether the information contained in the NMR spectrum is due to a physical phenomenon or a temperature change, and analysis accuracy deteriorates.

Conventionally, a method has been adopted in which the above-mentioned phase change occurring in the middle of a circuit is converted into a frequency axis by a computer, and then the phase is adjusted manually or automatically by the computer.

[Problem that the invention seeks to solve]

However, phase matching using the method described above is
Since conversion diameter correction is performed on the frequency spectrum, it takes extra time, and when the signal-to-noise ratio of the spectrum is poor, it is difficult to automatically correct the phase programmatically.

The present invention solves the above problems, and
It is an object of the present invention to provide an automatic phase correction method for a nuclear magnetic resonance apparatus that can correct phase changes even when an R signal is input.

[Means for solving problems]

To this end, the automatic phase correction method in the nuclear magnetic resonance apparatus of the present invention obtains a high frequency output for nuclear magnetic resonance excitation, power amplifies the high frequency output, applies it to a detection coil for excitation of nuclear magnetic resonance signals, and then In a nuclear magnetic resonance apparatus that detects a nuclear magnetic resonance signal, performs phase control using a phase control means, detects the nuclear magnetic resonance signal using two phase detection means having a 90° phase difference, and extracts the nuclear magnetic resonance signal, the high frequency output is set to a low level. and calculating means for calculating a phase error from the outputs of the two phase detection means, and when a low level high frequency output is applied, the calculation means calculates the phase of the output of the detection means. This method is characterized in that the phase is corrected by calculating the error and controlling the phase control means.

[Effect]

In the automatic phase correction method in the nuclear magnetic resonance apparatus of the present invention, the high-frequency output is applied to the detection coil at a low level by the high-frequency output applying means, and at this time, the detection coil detects it and the phase is controlled by the phase control means. 2 with phase difference
The calculation means calculates the phase error of the signal detected by the two phase detection means.

Since the phase control means is controlled based on this calculated phase error to perform phase correction, even during NMR signal detection, the high frequency output application means can apply high frequency output to the detection coil using a short timing time to correct the phase.

〔Example〕

Examples will be described below with reference to the drawings.

FIG. 1 is a diagram for explaining one embodiment of an automatic phase correction method in a nuclear magnetic resonance apparatus according to the present invention, and FIG.
3 is a time chart for explaining gate operations during excitation, signal detection, and phase correction of the nuclear magnetic resonance apparatus shown in the figure.

In Figure 1, l is an NMR detector, 2.4 and 6 are high frequency amplifiers, 3.5, 25 and 27 are frequency mixers, 7 and 8
is a phase detector, 9 and 10 are low frequency amplifiers, 11.12.
18 and 19 are AD converters, 13 is a computer, 1
4 and 15 are amplifiers for phase error detection, 16 and 17 are band-pass filters, 20 is an arithmetic circuit for phase error calculation, 21 is a low frequency oscillator, 22 and 24 are phase control circuits, 23 and 28
is a local oscillator, 26 is an amplifier, 29 is a phase error detection high frequency amplifier, 30 is an NMR signal excitation amplifier, 31 is a reflection component detector, 32 is a voltage generator, 33 is a voltage variable capacitor, and G1-G12 are gates. Shows the circuit.

Regarding the automatic phase correction method in the nuclear magnetic resonance apparatus according to the present invention, the circuit diagram of the excitation and detection system shown in FIG.
This will be explained with reference to the time chart shown in the figure.

Timing time t, ~1. shown in FIG. In this case, a low frequency signal is generated by a low frequency oscillator 21 and guided to a frequency mixer 25, and a local frequency for an intermediate frequency is generated by a local oscillator 23, gated by a gate circuit G5, and guided to a frequency mixer 25. be guided. These signals create an intermediate frequency in the frequency mixer 25, are gated again in the gate circuit G6, and are guided to the amplifier 26 and amplified. amplifier 2
The output of 6 is mixed with the output of the local oscillator 28 by a frequency converter 27, and the frequency mixer 27 outputs a high frequency wave for NMR excitation. In addition, the output of the local oscillator on the second day is G
The high frequency output for NMR excitation produced by the 0 frequency mixer 27 is gated at gate G10 and guided to the frequency mixer 27.
The output from the NMR detection detector is applied via gate G11. In this way, a high frequency wave for NMR excitation is applied to the detection coil for excitation of the NMR signal in the NMR detector 1 at a timing time t of ~1° as shown in FIG.

Next, timing time 1. ~1. The NMR signal induced by the high frequency for NMR excitation and output on the NMR detection detector is preamplified by the high frequency amplifier 2 at timing t, and then guided to the frequency mixer 3. This preamplified signal is mixed with the local oscillation output of the local oscillator 23 and outputs an intermediate frequency to the high frequency amplifier 4.

The output amplified by the high frequency amplifier 4 is guided to the frequency mixer 5, where it is converted into a second intermediate frequency. Note that this second intermediate frequency is mixed with the output of the local oscillator 23 whose phase is controlled by the phase control circuit 24, and the second intermediate frequency is
is guided to a high frequency amplifier 6. The output of the high frequency amplifier 6 is divided into two and guided to a phase detector 7.8.A detection frequency having a phase difference of 90° is applied to the zero phase detector 7.8 by a phase controller 22. The NMR signal is mixed with these frequencies and outputs an NMR signal with a 90° phase difference. These NMR signals are applied to gate circuits G1 and G2, respectively.
and is led to a low frequency amplifier 9.10. Each signal amplified by the low frequency amplifiers 9.10 is sent to an AD converter 11.
12, which is analog-to-digital converted and then led to a computer 13, is a circuit system for excitation and NMR signal detection.

On the other hand, during the detection of the NMR signal, the timing time t4~iss! shown in FIG. &~Lff, il~t9,...
... to switch the gate circuits 01 to G9, and amplify the high frequency output for NMR excitation produced by the frequency mixer 27 with the phase error detection high frequency amplifier 29,
In addition to the high power high frequency output for R excitation, a weak high frequency is
R is applied to the detector 1. At this time, the outputs of the phase detectors 7.8 whose phases are shifted by 90 degrees from each other are gate circuits G3 and G4.
The signal is led to phase error detection amplifiers 14 and 15 via. The signal amplified by the phase error detection amplifier 14.15 is band-limited by the bandpass filter 16.17, and then
The signals are respectively guided to AD converters 18 and 19, subjected to analog-to-digital conversion, and output to the arithmetic circuit 20 for phase error calculation. The phase error calculation arithmetic circuit 20 generates a phase control feedback signal and applies it to the phase control circuit 24 so that the output of the AD converter 18 is the maximum positive value and the output of the AD converter 19 is the minimum absolute value.

As described above, in the automatic phase correction method in the nuclear magnetic resonance apparatus according to the present invention, a high frequency wave for phase shift detection is generated at a frequency higher than the clock frequency of the AD converter normally measured, and when this high frequency wave for phase detection is generated, The gate circuit of the low frequency amplifier for NMR signal observation is closed. In addition, after phase detection and before entering the low frequency amplifier, the original NMR signal system and the phase difference detection system are separated to prevent a drop in signal response that would occur when the signal is passed through the low frequency amplifier. The phase of the change is detected.

By the way, if the resonance point of the NMR detector 1 shifts due to a temperature change or the like, no absorption occurs and the reflection becomes thick (this is why the reflection component detector 31 is provided to detect the reflection component from the NMR detector 1). This is what is being done.

The voltage generator 32 receives the detection output of the reflected component and controls the voltage applied to the voltage variable capacitor 33 so that the reflected component is minimized.

Note that the present invention can be modified in various ways and is not limited to the above embodiments. For example, the AD in FIG.
The configuration of the converters 18 and 19 may use diode detection to obtain phase information, and the phase control may be performed at the output of the local oscillator 28 instead of the output of the local oscillator 23. The phase of the NMR excitation high frequency side may be controlled.Furthermore, instead of separately providing the phase error detection high frequency amplifier 29 with a small amplification degree as shown in FIG. A variable attenuator may also be used.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, NM
Since the phase is corrected using the minute timing time during the R signal input, it is possible to correct the phase change on the excitation high frequency generation side and the phase change in the actual setting of the detection and amplification system including the probe.

[Brief explanation of drawings]

FIG. 1 is a diagram for explaining one embodiment of an automatic phase correction method in a nuclear magnetic resonance apparatus according to the present invention, and FIG.
3 is a time chart for explaining gate operations during excitation, signal detection, and phase correction of the nuclear magnetic resonance apparatus shown in the figure. 1...NMR detector, 2.4 and 6...high frequency amplifier, 3.5.25 and 27...frequency mixer, 7 and 8...
・Phase detector, 9 and 10...Low frequency amplifier, 11.1
2.18 and 19...AD converter, 13...computer, 14 and 15...phase error detection amplifier, 1
6 and 17...Bandpass filter, 20...Arithmetic circuit for phase error calculation, 21...Low frequency oscillator, 22 and 2
4... Phase control circuit, 23 and 28... Local oscillator,
26... Amplifier, 29... Phase error detection high frequency amplifier, 30... NMR signal excitation amplifier, 31...
Reflection component detector, 32... Voltage generator, 33... Voltage variable capacitor, Gl to G12... Gate circuit.

Claims (4)

[Claims] (1) Obtain a high frequency output for nuclear magnetic resonance excitation, power amplify the high frequency output and apply it to a detection coil for nuclear magnetic resonance signal excitation, then detect the nuclear magnetic resonance signal and phase it with a phase control means. In a nuclear magnetic resonance apparatus that performs control and extracts a nuclear magnetic resonance signal by detecting it with two phase detection means having a 90° phase difference, a high-frequency output applying means for applying the high-frequency output to a detection coil at a low level; comprising calculation means for calculating a phase error from the outputs of two phase detection means;
An automatic phase correction method in a nuclear magnetic resonance apparatus, characterized in that when a low-level high-frequency output is applied, the calculation means calculates a phase error in the output of the detection means and controls the phase control means to correct the phase. (2) In the nuclear magnetic resonance apparatus according to claim 1, wherein the high-frequency output applying means has an amplification means with a low amplification degree and a gate circuit, and is configured to be switched with the power amplification means. Automatic phase correction method. (3) The automatic phase in the nuclear magnetic resonance apparatus according to claim 2, wherein the high frequency output applying means switches the gate circuit using a predetermined timing time while detecting the nuclear magnetic resonance signal. Correction method. (4) The calculation means calculates the output obtained from the two phase detection means through the amplification means, the bandpass filter, and the analog/digital conversion means, and determines that one output is the maximum in positive value and the output of the other is the minimum in absolute value. An automatic phase correction system in a nuclear magnetic resonance apparatus according to claim 1, characterized in that the phase control means is controlled so that the phase control means is controlled so that