JP2010025895A - Nuclear magnetic resonance apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a low cost and space-saving NMR apparatus which can utilize effectively a triple resonance probe which has only two ports. <P>SOLUTION: In the nuclear magnetic resonance apparatus equipped with a high frequency generating circuit which mixes a local frequency which is generated in a local frequency oscillator and a medium frequency which is generated in a medium frequency generating circuit, and generates high frequency for observation, the nuclear magnetic resonance apparatus comprises a first high frequency generating circuit which mixes the local frequency LO1 which is generated in the local frequency oscillator and the medium frequency IF which is generated in the medium frequency generating circuit and generates the high frequency RF1 having the resonance frequency of a first nucleus, a conversion circuit which converts the local frequency LO1 which is generated in the local frequency oscillator into a second local frequency LO2 of different frequency, and a second high frequency generating circuit which mixes the local frequency LO2 obtained from the conversion circuit and the medium frequency IF which is generated in the medium frequency generating circuit, and generates the high frequency RF2 having the resonance frequency of a second nucleus. And the nuclear magnetic resonance measurement is performed using the high frequency RF1 and the high frequency RF2. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a nuclear magnetic resonance (NMR) apparatus provided with an RF generation circuit.

  The NMR device irradiates a sample to be measured placed in a static magnetic field with a high-frequency signal, then detects a minute high-frequency signal (NMR signal) emitted from the sample to be measured, and the molecular structure information contained therein Is a device for analyzing molecular structure by extracting. Among these, the transmission system is referred to until the high-frequency signal is irradiated on the sample to be measured, and the reception system after the irradiation until the NMR signal is detected from the sample to be measured and the molecular structure is analyzed.

As an example, FIG. 1 shows a schematic diagram of a transmission system of a basic NMR apparatus using a superheterodyne method. In an NMR apparatus, the resonance conditions are determined by the gamma value of each nucleus and the static magnetic field strength of the superconducting magnet. The most common apparatus configuration is mainly hydrogen nuclei ( ¹ H) and fluorine nuclei ( ¹⁹ F). ) And an LF channel for exciting a nucleus having a resonance frequency lower than that of a phosphorus nucleus ( ³¹ P) are known.

  Although the above channels can be arbitrarily added according to the purpose of NMR measurement, FIG. 1 shows a basic configuration of two channels for explanation. The description of FIG. 1 will be described below.

  Reference numeral 1 denotes a control signal line for controlling the apparatus, for example, a control line by an upper computer (upper control function) or the like.

  Reference numerals 2 and 2a are control circuits (hereinafter referred to as sequencers) for controlling a pulse sequence for measurement. For example, reference numerals 2 and 2a are necessary for measurement via a control line 1 from a host computer or the like. The information is received, and the intermediate frequency generation circuits 3, 3a, the RF generation circuits 5, 5a and the power amplifiers 6, 6a, which will be described later, are controlled. It is also possible to control the local oscillators 4 and 4a. Depending on the pulse sequence to be measured and the device configuration, a plurality of sequencers 2 and 2a may be required.

  Reference numerals 3 and 3a are intermediate frequency generation circuits that generate an intermediate frequency (IF) using, for example, a direct digital synthesizer (DDS). In FIG. 1, as an example, the intermediate frequency is set to an arbitrary value of 9 MHz to 12 MHz.

  In the figure, information on the intermediate frequency generated by the intermediate frequency generation circuits 3 and 3a is received from the sequencers 2 and 2a, and depending on the apparatus, function waveform shaping, amplitude setting, frequency / phase switching, and the like are performed.

  Further, depending on the pulse sequence and apparatus, a plurality of intermediate frequency generation circuits 3 and 3a may be required. The intermediate frequency is generally used for the intermediate frequency for heterodyne detection in the receiving circuit, but the receiving circuit is omitted in FIG.

  Note that, as an example, the sequencers 2 and 2a and the intermediate frequency generation circuits 3 and 3a are described separately, but these functions may be integrated.

  Next, reference numerals 4 and 4a are local oscillators. In the case of the NMR apparatus, depending on the strength of the static magnetic field and the type of the measurement nucleus, in the case of FIG. 1, for example, an arbitrary frequency between about 10 kHz and about 1 GHz. A local frequency (LO) can be generated, and an output frequency with high purity and excellent phase noise is desired.

  Information on the local frequency generated by the local oscillators 4 and 4a is received from the host computer via the control line 1 and output a predetermined frequency, for example, as in the example of FIG.

  As an example, the sequencers 2 and 2a and the local oscillators 4 and 4a are described separately, but these functions may naturally be integrated.

  The local frequency output is used for the local frequency of the heterodyne detection in the receiving circuit in addition to the transmission system, but the reception system is omitted in this figure.

Basically, one local oscillator can be measured for one measurement nucleus. For example, in the case of ¹³ C- { ¹ H} measurement, since the observation nucleus is a carbon nucleus and the irradiation nucleus is a hydrogen nucleus, the type of nucleus is two and two local oscillators are required.

  Reference numerals 5 and 5a denote RF generation circuits for generating a resonance frequency for exciting the measurement nucleus. For example, a mixer is used to multiply the intermediate frequency and the local oscillation frequency to obtain the resonance frequency of the measurement nucleus. RF of the same frequency is generated.

  Further, depending on the pulse sequence and apparatus, a plurality of RF generation circuits 5 and 5a may be required.

  The outputs of these RF generation circuits 5 and 5a are input to power amplifiers 6 and 6a, amplified to a size suitable for measurement, and the amplified outputs are guided to transmission / reception switching circuits 7 and 7a to reach the probe 8. To do. Of course, the object to be measured is contained in the probe 8, and the measured nucleus is excited by the applied power to obtain an NMR signal.

  The obtained NMR signal is guided to the preamplifier via the transmission / reception switching circuits 7 and 7a, and after sufficient amplification, is transmitted to the reception circuit.

  The probe 8 in FIG. 1 is, for example, a general tunable probe having one HF port and one LF port. Therefore, in FIG. 1, the frequency generation circuit serving as the excitation source requires two channels, HF channel and LF channel, surrounded by a dotted line.

Naturally, in the triple resonance probe (HCN triple resonance probe) that can excite triple resonance for ¹ H nucleus, ¹³ C nucleus, and ¹⁵ N nucleus, another LF channel for ¹⁵ N nucleus is added. It will be. In addition, in the triple resonance probe (CFH triple resonance probe) capable of exciting triple resonance for ¹³ C nucleus, ¹⁹ F nucleus and ¹ H nucleus, another channel for ¹⁹ F nucleus is added. It will be.

JP 2002-214314 A.

  As the basic NMR source excitation source configuration, there are many HF channels and LF channels, and in the case of triple resonance measurement, the necessary excitation source channel should be added to the device. Is possible. However, in the case of a general-purpose device with a reduced price, the excitation source is limited to a single channel configuration of HF / LF, and channels may not be added.

  For example, in the case of a CFH triple resonance probe, the probe generally includes a first HF port (mainly tuned to a hydrogen nucleus), a second HF port (mainly tuned to a fluorine nucleus), an LF port (mainly a carbon nucleus). A total of three ports are provided.

  In this case, the excitation source requires a total of three channels, the HF2 channel and the LF1 channel, for the spectrometer.

  FIG. 2 shows an example of a spectrometer having a three-channel configuration. Reference numerals 2 to 7 are the same as those in FIG. Further, since reference numerals 2a to 7a are the same as those in FIG. 1, they are omitted in FIG.

  This is a second HF channel to which symbols 2b to 7b are added. Reference numeral 2b means a sequencer as in reference numeral 2. Similarly, reference numeral 3b denotes an intermediate frequency generation circuit, reference numeral 4b denotes a local oscillator, reference numeral 5b denotes an RF generation circuit, reference numeral 6b denotes a power amplifier, and reference numeral 7b denotes a transmission / reception switching circuit. Respectively.

  It can be seen that reference numeral 8 is a CFH triple resonance probe, and the probe has a total of three ports, a first HF port, a second HF port, and an LF port.

  Even in the same CFH triple resonance probe, depending on the structure of the probe, a circuit in which two nuclei, a hydrogen nucleus and a fluorine nucleus are tuned, is mounted on the HF port, and the LF port is mainly tuned to the carbon nucleus as in the past Some probes have a total of 2 ports. Even in this case, a total of three channels of HF2 channel and LF1 channel are required for the spectrometer. An example of a spectrometer configuration in such a case is shown in FIGS.

  First, in the example of FIG. 3, the configuration is almost the same as that of FIG. 2, but the probe 8c has only one HF / LF port as described above and has a total of 2 ports. Measurement can be performed by switching the outputs of the power amplifier 6 and the second HF channel power amplifier 6b and combining them with a combiner or the like. Since the LF channel is the same as in FIG. 1, it is omitted.

  However, in the case of the configuration example of the spectrometer as shown in FIG. 3, the power amplifier 6b must be prepared in the spectrometer, resulting in a problem that the cost is increased and a space for storing the additional circuit is required. is there.

  Therefore, an example as shown in FIG. 4 is also conceivable. In the example of FIG. 4, a local oscillator 4c is basically added to the configuration of the spectrometer of FIG.

  For example, the local oscillator 4 outputs the local frequency of the hydrogen nucleus and multiplies it with one of the intermediate frequency generation circuits 3 to generate the resonance frequency of the hydrogen nucleus, and the additional local oscillator 4c generates the fluorine nucleus. The local frequency is output and multiplied by one of a plurality of intermediate frequency generation circuits 3 to generate the resonance frequency of the fluorine nucleus, and the two are switched or synthesized by a combiner or the like, and the power amplifier 6 To input. Since the LF channel is the same as in FIG. 1, it is omitted.

  However, even in the case of FIG. 4, the local oscillator 4c must be newly added, and there are problems in terms of cost and space.

  As described above, a small general-purpose spectrometer has one channel each for HF / LF, but there are many cases where there is no space for adding more channels, and the second HF as shown in FIGS. It was difficult to add channels.

  Also, a local oscillator with a wide band and good phase noise characteristics is very expensive, and a power amplifier is also expensive.

  The present invention has been made in view of the above points, and an object of the present invention is to provide an inexpensive and space-saving NMR apparatus capable of effectively utilizing a triple resonance probe having only two ports.

In order to achieve this object, the NMR apparatus of the present invention comprises:
In a nuclear magnetic resonance apparatus including a high frequency generation circuit that generates a high frequency for observation by mixing a local frequency generated by a local oscillator and an intermediate frequency generated by an intermediate frequency generation circuit,
A first high frequency generation circuit that generates a high frequency RF1 having a resonance frequency of the first nucleus by mixing the local frequency LO1 generated from the local oscillator and the intermediate frequency IF generated by the intermediate frequency generation circuit;
A conversion circuit for converting a local frequency LO1 generated from the local oscillator into a second local frequency LO2 having a different frequency;
A second high frequency generation circuit for generating a high frequency RF2 having a resonance frequency of the second nucleus by mixing the local frequency LO2 obtained from the conversion circuit and the intermediate frequency IF generated by the intermediate frequency generation circuit; ,
And nuclear magnetic resonance measurement is performed using the high-frequency RF1 and RF2.

  Further, the conversion circuit includes a difference frequency generation circuit that generates a difference frequency DF between the LO1 and the LO2, and the difference frequency DF and the LO1 are mixed to generate the LO2.

  Further, the difference frequency generating circuit is a direct digital synthesizer.

  The conversion circuit includes a voltage-controlled oscillator that generates a second local frequency LO2 that is necessary when generating a high frequency RF2 having a second nuclear resonance frequency from the first local frequency LO1. A programmable phase comprising a phase comparison circuit for comparing the phase of the oscillation output of the voltage controlled oscillator and the local frequency LO1, and forming the phase locked loop by sending the output of the phase comparison circuit to the voltage controlled oscillator -It features a locked loop synthesizer.

According to the NMR apparatus according to the present invention,
In a nuclear magnetic resonance apparatus including a high frequency generation circuit that generates a high frequency for observation by mixing a local frequency generated by a local oscillator and an intermediate frequency generated by an intermediate frequency generation circuit,
A first high frequency generation circuit that generates a high frequency RF1 having a resonance frequency of the first nucleus by mixing the local frequency LO1 generated from the local oscillator and the intermediate frequency IF generated by the intermediate frequency generation circuit;
A conversion circuit for converting a local frequency LO1 generated from the local oscillator into a second local frequency LO2 having a different frequency;
A second high frequency generation circuit for generating a high frequency RF2 having a resonance frequency of the second nucleus by mixing the local frequency LO2 obtained from the conversion circuit and the intermediate frequency IF generated by the intermediate frequency generation circuit; ,
Since the nuclear magnetic resonance measurement was performed using the high-frequency RF1 and RF2,
It has become possible to provide an inexpensive and space-saving NMR apparatus that can effectively utilize a triple resonance probe having only two ports.

  Hereinafter, the best mode according to the present invention will be described with reference to the drawings.

  FIG. 5 shows an embodiment of the NMR apparatus according to the present invention. Note that FIG. 5 picks up only the HF channel which is the main part of the present invention, and the LF channel is omitted because it is the same as reference numerals 2a to 7a in FIG.

  Reference numeral 1 denotes a control signal line for controlling the apparatus, for example, a control line by an upper computer (upper control function) or the like.

  Next, reference numeral 2 is a control circuit (hereinafter referred to as a sequencer) for controlling a pulse sequence for measurement. As an example, information necessary for measurement is transmitted from a host computer or the like via the control line 1. Upon receipt, control of an intermediate frequency generation circuit 3, an RF generation circuit 5, a power amplifier 6, an RF generation circuit 9, and the like described later is performed. It is also possible to control the local oscillator 4. Depending on the pulse sequence to be measured and the device configuration, a plurality of sequencers 2 may be required.

  Reference numeral 3 denotes an intermediate frequency generation circuit which generates an intermediate frequency (IF frequency) using, for example, a direct digital synthesizer (DDS). In FIG. 5, as an example, the intermediate frequency is set to an arbitrary value of 9 MHz to 12 MHz.

  In the figure, information on the intermediate frequency generated by the intermediate frequency generation circuit 3 and the RF generation circuit 9 is received from the sequencer 2, and depending on the apparatus, function waveform shaping, amplitude setting, frequency / phase switching, and the like are performed.

  Further, depending on the pulse sequence and the apparatus, a plurality of intermediate frequency generation circuits 3 and RF generation circuits 9 may be required. The intermediate frequency is generally used for the intermediate frequency for heterodyne detection in the receiving circuit, but the receiving circuit is omitted in FIG.

  As an example, the sequencer 2, the intermediate frequency generation circuit 3, and the RF generation circuit 9 are described separately, but these functions may be integrated.

  Next, reference numeral 4 denotes a local oscillator. In the case of the NMR apparatus, depending on the strength of the static magnetic field and the type of the measurement nucleus, in the case of FIG. 5, for example, an arbitrary local oscillation frequency between about 10 kHz and about 1 GHz. A frequency (LO) can be generated, and an output frequency with high purity and excellent phase noise is desired.

  The local frequency information generated by the local oscillator 4 is received from the host computer via the control line 1 as shown in the example of FIG. 5, for example, and a predetermined frequency is output.

  As an example, the sequencer 2 and the local oscillator 4 are described separately, but these functions may be integrated.

  The local frequency output is used for the local frequency of the heterodyne detection in the receiving circuit in addition to the transmission system, but the reception system is omitted in this figure.

  Basically, one local oscillator can be measured for one measurement nucleus.

  Next, reference numeral 5 denotes an RF generation circuit that generates a resonance frequency for exciting the measurement nucleus. For example, a mixer is used to multiply the intermediate frequency and the local oscillation frequency to generate an RF frequency that is a resonance frequency. To do.

  Further, depending on the pulse sequence and apparatus, a plurality of RF generation circuits 5 may be required.

  The outputs of these RF generation circuits 5 are input to a power amplifier 6 and amplified to a size suitable for measurement. The amplified outputs are guided to a transmission / reception switching circuit 7 and reach a probe 8c. Of course, the object to be measured is contained in the probe 8c, and the measured nucleus is excited by the applied power to obtain an NMR signal.

  The obtained NMR signal is guided to the preamplifier via the transmission / reception switching circuit 7, sufficiently amplified, and then transmitted to the receiving circuit.

  Next, the code 8c is equipped with a circuit in which two nuclei of hydrogen nucleus and fluorine nucleus are tuned in the HF port, and the LF port is tuned mainly to the carbon nucleus as in the past. This is a prepared probe.

For example, in the case of ¹ H- { ¹⁹ F} { ¹³ C} measurement, when exciting a hydrogen nucleus as an observation nucleus, a local oscillation frequency corresponding to the hydrogen nucleus is output from the local oscillator 4 and controlled by the sequencer 2. The intermediate frequency generation circuit 3 outputs an intermediate frequency such that the result of mixing with the local frequency becomes the resonance frequency of the hydrogen nucleus. These are multiplied by the RF generation circuit 5 to become the resonance frequency of the hydrogen nucleus, amplified to a size suitable for measurement by the power amplifier 6, and then applied to the HF port of the probe 8c via the transmission / reception switching circuit 7. Thus, the hydrogen nucleus is excited.

  When the carbon nuclei are excited for decoupling, which is omitted in FIG. 5, the resonance frequency of the carbon nuclei is generated and amplified by the same method as 2a to 7a in FIG. 1, and is applied to the LF port of the probe 8c. Apply.

  When the fluorine nucleus is excited for decoupling, the local frequency for the hydrogen nucleus output from the local oscillator 4 is supplied to another RF generation circuit 9 newly provided at the same position as the RF generation circuit 5 described above. , The resonance frequency of the fluorine nucleus is generated by the RF generation circuit 9, amplified to a size suitable for measurement by the power amplifier 6, and then applied to the HF port of the probe 8 c via the transmission / reception switching circuit 7.

  Hereinafter, the RF generation circuit 9 will be described in more detail. FIG. 6 is a schematic diagram of the RF generation circuit 5 of FIGS. 1 to 5 described above.

  The RF generator circuit 5 may have various additional functions such as a gain control circuit and a gate circuit depending on the manufacturer of the NMR apparatus, but the main purpose is to mix the intermediate frequency and the local frequency.

  FIG. 7 shows an example of the circuit configuration of the RF generator circuit 9 of FIG. 5, which incorporates a new idea based on the RF generator circuit 5 of FIG.

  The code | symbol A is a direct digital synthesizer (DDS), Comprising: The frequency required in order to obtain the local frequency for fluorine nuclei from the local frequency for hydrogen nuclei is generated.

  If the resonance frequency of the hydrogen nucleus is 470 MHz, assuming that the resonance frequency of the hydrogen nucleus is 500 MHz, the local frequency for the hydrogen nucleus is 511 MHz if the intermediate frequency for the hydrogen nucleus is 11 MHz. . Therefore, the codes 4 to 511 MHz of FIG. 5 are input to the mixer of the code b of FIG.

  Assuming that the intermediate frequency for the fluorine nucleus is 10.5 MHz, the local frequency for the fluorine nucleus is 480.5 MHz because it is necessary to obtain the resonance frequency of the fluorine nucleus, which is 480.5 MHz. 30.5 MHz, which is the difference frequency (DF) between the local frequency and the local frequency for the fluorine nucleus, is output.

  As an example, the DDS of the code A uses a high-performance clock that is common to the local oscillator for hydrogen nuclei, and a high-purity frequency that is almost comparable to the purity of the local frequency for hydrogen nuclei. 30.5 MHz can also be output.

  As a result, the mixing frequency of 511 MHz for the hydrogen nucleus and the 30.5 MHz generated by the DDS of the code A are mixed by the Mixer of the code B in FIG. 7, and only the high-purity 480.5 MHz component is If it is taken out with a pass filter and finally mixed with an intermediate frequency of 10.5 MHz for fluorine nuclei using a mixer with a sign D, it becomes possible to obtain a resonance frequency of 470 MHz for high-purity fluorine nuclei.

  The output frequency data setting of the DDS of the code A may be a fixed value, or may be set from the upper computer via the control signal line 1.

  The former allows measurement without changing the spectrometer control of the existing host computer, but is not flexible. On the other hand, the latter requires some additional functions, but allows for flexible handling.

  The above has been described focusing on the case of the CFH triple resonance probe. However, if this embodiment is applied, the present invention is not limited to the NMR probe having a plurality of HF ports such as the CFH triple resonance probe, but the HCN triple resonance probe. The present invention can also be applied to an NMR probe having a plurality of such LF ports.

  Further, in the present embodiment, an example in which another local frequency is generated using the local frequency for the hydrogen nucleus is shown, but the original local frequency is not necessarily the local frequency for the hydrogen nucleus. There is no need. For example, it goes without saying that the local frequency for the hydrogen nucleus may be generated based on the local frequency for the fluorine nucleus.

  Although the overall configuration is the same as that shown in FIG. 5, a modification of the RF generation circuit indicated by reference numeral 9 will be described below.

  FIG. 8 shows another embodiment of the RF generation circuit 9, and incorporates a new idea based on the RF generation circuit shown in FIG.

  In the figure, symbol “H” is a programmable phase locked loop synthesizer (hereinafter abbreviated as “programmable PLL synthesizer”). Phase-locked with the frequency to generate the frequency necessary to obtain the local frequency for the fluorine nucleus.

  If the resonance frequency of the hydrogen nucleus is 500 MHz and the resonance frequency of the fluorine nucleus is 470 MHz, the local frequency for the hydrogen nucleus is 512 MHz if the intermediate frequency for the hydrogen nucleus is 12 MHz.

  Assuming that the intermediate frequency for the fluorine nucleus is 12 MHz, the local oscillation frequency for the fluorine nucleus is 482 MHz, and a VCO that can output 482 MHz is used.

  The code PLL programmable PLL synthesizer has, for example, a circuit that divides the local frequency 512 MHz for hydrogen nuclei into 1 / M and a circuit that divides the input from the VCO into 1 / N. Then, for example, phase comparison is performed at 1 MHz with M = 512 and N = 482, and the direct current output is sent to the VCO to the code to control the oscillation frequency, so that the high purity local frequency for the hydrogen nucleus is controlled. It becomes possible to phase lock the local frequency for the fluorine nucleus. Thereby, a stable VCO output can be obtained without reducing the purity of the output frequency.

  If the VCO output to the code is filtered by a band pass filter of the code, only a high-purity 482 MHz component can be extracted. By mixing it with the intermediate frequency for fluorine nuclei with a mixer of the code H, it becomes possible to obtain a high-purity resonance frequency for the fluorine nuclei.

  The frequency division data setting of the programmable PLL synthesizer of code E may be a fixed value, or may be output frequency data setting from a host computer via the control signal line 1.

  The former allows measurement without changing the spectrometer control of the existing host computer, but is not flexible. On the other hand, the latter requires some additional functions, but allows for flexible handling.

  The above has been described focusing on the case of the CFH triple resonance probe. However, if this embodiment is applied, the present invention is not limited to the NMR probe having a plurality of HF ports such as the CFH triple resonance probe, but the HCN triple resonance probe. The present invention can also be applied to an NMR probe having a plurality of such LF ports.

  Further, in the present embodiment, an example in which another local frequency is generated using the local frequency for the hydrogen nucleus is shown, but the original local frequency is not necessarily the local frequency for the hydrogen nucleus. There is no need. For example, it goes without saying that the local frequency for the hydrogen nucleus may be generated based on the local frequency for the fluorine nucleus.

  As described above, when triple resonance is performed in a spectrometer system having only one HF / LF channel, conventionally, measurement cannot be performed unless at least one channel of a local oscillator is added. In this proposal, the RF generation circuit is provided with a function of outputting the local frequency for other nuclei based on the local frequency for hydrogen nuclei, for example, thereby significantly reducing costs and increasing the purity of the obtained RF. Space can be saved with little reduction.

  It can be widely used in NMR apparatuses for the purpose of multinuclear measurement.

It is a figure which shows an example of the conventional NMR apparatus. It is a figure which shows an example of the conventional NMR apparatus. It is a figure which shows an example of the conventional NMR apparatus. It is a figure which shows an example of the conventional NMR apparatus. It is a figure which shows one Example of the NMR apparatus concerning this invention. It is a figure which shows one part of RF generator circuit for NMR apparatuses concerning this invention. It is a figure which shows one part of RF generator circuit for NMR apparatuses concerning this invention. It is a figure which shows one part of RF generator circuit for NMR apparatuses concerning this invention.

Explanation of symbols

1: control signal line, 2: sequencer, 2a: sequencer, 2b: sequencer, 3: intermediate frequency generation circuit, 3a: intermediate frequency generation circuit, 3b: intermediate frequency generation circuit, 4: local oscillator, 4a: local oscillator, 4b : Local oscillator, 4c: local oscillator, 5: RF generation circuit, 5a: RF generation circuit, 5b: RF generation circuit, 6: power amplifier, 6a: power amplifier, 6b: power amplifier, 7: transmission / reception switching circuit, 7a: Transmission / reception switching circuit, 7b: Transmission / reception switching circuit, 8: Probe, 8a: Probe, 8b: Probe, 9c: Probe, 9: RF generation circuit, A: DDS, B: Mixer, C: Band pass filter, D: Mixer, E: Programmable PPL synthesizer, F: VCO, G: Band pass filter

Claims (4)

In a nuclear magnetic resonance apparatus including a high frequency generation circuit that generates a high frequency for observation by mixing a local frequency generated by a local oscillator and an intermediate frequency generated by an intermediate frequency generation circuit,
A first high frequency generation circuit that generates a high frequency RF1 having a resonance frequency of the first nucleus by mixing the local frequency LO1 generated from the local oscillator and the intermediate frequency IF generated by the intermediate frequency generation circuit;
A conversion circuit for converting a local frequency LO1 generated from the local oscillator into a second local frequency LO2 having a different frequency;
A second high frequency generation circuit for generating a high frequency RF2 having a resonance frequency of the second nucleus by mixing the local frequency LO2 obtained from the conversion circuit and the intermediate frequency IF generated by the intermediate frequency generation circuit; ,
And a nuclear magnetic resonance apparatus using the high-frequency RF1 and RF2. 2. The conversion circuit includes a difference frequency generation circuit that generates a difference frequency DF between the LO1 and the LO2, and generates the LO2 by mixing the difference frequency DF and the LO1. The nuclear magnetic resonance apparatus described. The nuclear magnetic resonance apparatus according to claim 2, wherein the differential frequency generation circuit is a direct digital synthesizer. The conversion circuit includes a voltage controlled oscillator that generates a second local frequency LO2 that is required when generating a high frequency RF2 having a second nuclear resonance frequency from the first local frequency LO1, and the voltage control. Programmable phase locked loop comprising a phase comparison circuit for comparing the phase of the oscillation output of the oscillator and the local frequency LO1, and forming the phase locked loop by sending the output of the phase comparison circuit to the voltage controlled oscillator The nuclear magnetic resonance apparatus according to claim 1, further comprising a loop synthesizer.

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