JP6943667B2 - NMR measuring device and reflected wave monitoring method - Google Patents

Description

The present invention relates to an NMR measuring device, and more particularly to monitoring reflected waves returning from a detection circuit.

NMR (nuclear magnetic resonance) is a phenomenon in which an atomic nucleus placed in a static magnetic field interacts with an electromagnetic wave having a frequency peculiar to the atomic nucleus. An NMR measuring device is a device for observing the phenomenon and analyzing a sample at the atomic level. The NMR measuring device is utilized in the analysis of organic compounds (for example, chemicals, pesticides), polymer materials (for example, vinyl, polyethylene), biological substances (for example, nucleic acids, proteins) and the like. By using an NMR measuring device, for example, it is possible to elucidate the molecular structure.

Prior to the NMR measurement, the detection circuit in the NMR measurement probe (detector) is adjusted manually or automatically. That is, tuning is performed. Here, tuning is a concept in a broad sense, that is, the concept of tuning includes tuning that matches the resonance frequency of the detection circuit with respect to a specific frequency (tuning in a narrow sense) and tuning of the detection circuit with respect to the output impedance of the transmission line. Matching to match the input impedance and is included. Generally, the detection circuit is provided with a tuning variable capacitor and a matching variable capacitor, and the best tuning state is formed by operating and adjusting them. Then the NMR measurement is carried out.

At the time of tuning, a reflected wave monitoring unit that detects the reflected wave returning from the detection circuit and calculates the level of the reflected wave is used. It generally forms part of an NMR measuring device. The reflected wave monitoring unit has a function of displaying the reflected wave level as a numerical value or a graph, and also indicates a signal indicating the reflected wave level to an auto tuner (see Patent Document 1) that automatically tunes. It has a function to output. When displaying the graph, the frequency of the transmitted signal is swept, and the level of the reflected wave is observed for each frequency. A graph (frequency characteristic) is generated by plotting them.

Patent Document 2 discloses that a 50Ω termination circuit is used instead of the NMR measurement probe when tuning the NMR measurement probe. However, Patent Document 2 does not disclose a technique for correcting or calibrating the level of the reflected wave returning from the NMR measurement probe.

Japanese Unexamined Patent Publication No. 11-218570 U.S. Pat. No. 4,593,246

When monitoring the reflected wave, it is desirable that the level of the transmitted wave reaching the detection circuit is uniform over a certain frequency range, but the transmitted wave at a specific frequency is affected by the frequency characteristics of the device and transmission path. Level may be higher or lower. Due to this, the level of the detected reflected wave changes. When tuning is performed while referring to the level of the reflected wave, if the level of the reflected wave changes regardless of the tuning as described above, accurate tuning cannot be performed. Further, the same problem as described above may occur when the characteristics of the device or the transmission path change due to factors such as a temperature change in the tuning process.

An object of the present invention is to provide reflected wave information that correctly reflects the tuning state at the time of tuning the detection circuit.

The NMR measuring device according to the embodiment is selected from a transmission / reception circuit that generates a transmission wave for tuning and receives a reflected wave, and a circuit group including an NMR detection circuit and a reference circuit for the transmission / reception circuit. The NMR detection circuit was selected based on the selection circuit for connecting the circuits, the acquisition means for acquiring the level of the reference reflected wave received with the reference circuit selected as the reference level, and the reference level. It includes a calculation means for calculating the standardization level by standardizing the level of the actual reflected wave received in the state.

According to the above configuration, the level of the reference reflected wave returning from the reference circuit is acquired as the reference level, and the level of the actual reflected wave returning from the NMR detection circuit (measured level) is standardized based on the reference level. The standardization level is calculated by this. The standardization level is provided (display, output, etc.). In this way, in manual or automatic tuning, the normalized level can be provided as the reflected wave level, so that the influence of the change in the transmitted wave level can be excluded or reduced. That is, according to the above configuration, it is possible to provide reflected wave information that correctly reflects the tuning state as compared with the conventional configuration.

It is possible to calculate the ratio of the transmitted wave level and the reflected wave level and provide it, but a special circuit is required to monitor them simultaneously and separately, which complicates the device configuration. easy. On the other hand, in the above configuration, the reference level and the measured level are acquired in time division. According to the above configuration, it is possible to obtain reliable reflected wave information with a relatively simple configuration or without monitoring the transmitted wave level.

Normalization is performed, for example, based on one reference level (for example, maximum level), and preferably based on a plurality of reference levels (for example, maximum level and minimum level). Usually, a number of reference circuits corresponding to the number of reference levels are provided. However, it is also possible to acquire a plurality of reference levels by changing the operating conditions of one reference circuit (in that case, a plurality of reference circuits logically exist). The reference circuit is a dummy circuit that replaces the NMR detection circuit. It is desirable to set a sequence for reflected wave monitoring so that the operation of the selection circuit and the like are automatically controlled according to the sequence.

In the embodiment, the circuit group includes a first reference circuit that causes total reflection or quasi-total reflection as the reference circuit, and the acquisition means is in a state where the first reference circuit is selected. The level of the received reference reflected wave is acquired as the first reference level. For example, the first reference circuit is an open end circuit. Semi-total reflection means strong reflection similar to total reflection that can be regarded as total reflection.

In the embodiment, the circuit group includes a second reference circuit that causes non-reflection or quasi-non-reflection as the reference circuit, and the acquisition means is in a state where the second reference circuit is selected. The level of the received reference reflected wave is acquired as the second reference level. For example, the second reference circuit is a terminal circuit having an impedance matching action. Semi-non-reflective means weak reflection similar to non-reflective, which can be regarded as non-reflective. A simple resistor may be provided as the termination circuit, but an electronic circuit including a resistor, a capacitor, a coil, or the like may be provided.

In the embodiment, the circuit group includes, as the reference circuit, a first reference circuit that causes total reflection or quasi-total reflection, and a second reference circuit that causes non-reflection or quasi-non-reflection. The acquisition means acquires the level of the reference reflected wave received with the first reference circuit selected as the first reference level, and the reference reflection received with the second reference circuit selected. The wave level is taken as the second reference level, and the calculation means is based on the ratio expressed by (actual reflected wave level-second reference level) / (first reference level-second reference level). Calculate the standardization level. The ratio may be multiplied by a scale factor (eg, the maximum value of the display range). In the actual display, the calculated standardization level may be logarithmically converted, and the value calculated thereby may be displayed on the logarithmic axis.

In the embodiment, the transmission / reception circuit generates a transmission wave while performing frequency sweep, the selection circuit sequentially selects a circuit from the circuit group according to the frequency sweep cycle, and the calculation means performs the frequency sweep. A means for generating a reference level frequency characteristic indicating a change in the reference level caused by the sweep, a means for generating an actually measured level frequency characteristic indicating a change in the level of the actual reflected wave caused by the frequency sweep, and the reference level. A means for generating a standardized level frequency characteristic representing a standardized level for each frequency by standardizing the measured level frequency characteristic based on the frequency characteristic is included. When the selection operation in the selection circuit requires a certain amount of time, if the selection circuit is operated for each frequency switching, it takes a considerable amount of time to obtain the normalized level frequency characteristic. According to the above configuration, the number of operations of the selection circuit can be reduced and the time required to obtain the standardized level frequency characteristic can be shortened.

In the embodiment, a complex conversion circuit for converting a signal representing the level of the reference reflected wave into a reference level signal in a complex format and converting a signal representing the level of the real reflected wave into a measured level signal in a complex format is included. The acquisition means acquires the real part reference level and the imaginary part reference level as the reference level based on the complex type reference level signal, and the calculation means sets the real part reference level and the imaginary part reference level. Based on this, the measured level signal in the complex form is standardized.

In the reflected wave monitoring method according to the embodiment, a circuit selected from a group of circuits including an NMR detection circuit and a reference circuit is connected to a transmission / reception circuit that generates a transmission wave for tuning and receives the reflected wave. The step, the step of acquiring the level of the reference reflected wave received with the reference circuit selected as the reference level, and the actual reception with the NMR detection circuit selected based on the reference level. It includes a step of calculating the standardization level by standardizing the level of the reflected wave. This method can be realized as a function of hardware or as a function of software. In the latter case, a program that realizes the function is installed in a device that monitors reflected waves via a network or a portable storage medium.

In the embodiment, the reflected wave monitoring method further includes a step of determining the necessity of reacquisition of the reference level based on the stability of the standardized level. The stability of the normalization level is the stability over time, and can be recognized as, for example, the magnitude of the difference between the standardization level calculated last time and the standardization level calculated this time. Therefore, for example, if the difference is large, it is highly likely that the tuning operation is actually performed, and if the difference is small, it is judged that the possibility that the tuning operation is actually performed is low, and the tuning operation is actually performed. The reference level may be reacquired during the period when the tuning operation is not performed, while the detection of the actual reflected wave may be prioritized during the period when the tuning operation is actually performed. As a result, the reflected wave level acquisition throughput during the tuning operation can be improved.

According to the present invention, it is possible to provide reflected wave information that correctly reflects the tuning state at the time of tuning the detection circuit.

It is a block diagram which shows the NMR measuring apparatus which concerns on embodiment. It is a figure which shows the method of normalizing the actual measurement level. It is a figure which shows the reflected wave level frequency characteristic. It is a figure which shows the effect by the standardization which concerns on embodiment. It is a figure which shows the configuration example of the receiving circuit and a local processor shown in FIG. It is a figure which shows the 1st operation example. It is a figure which shows the 2nd operation example. It is a figure which shows the 3rd operation example. It is a figure which shows the 1st modification. It is a figure which shows the 2nd modification.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows the overall configuration of the NMR measuring apparatus according to the embodiment as a block diagram. This NMR measuring device is a device used when analyzing a sample or the like. The NMR measuring device includes a spectrometer main body 10, an NMR measuring probe 24, and a reflected wave monitoring unit 30. The reflected wave monitoring unit 30 functions when tuning the detection circuit 26 in the NMR measurement probe 24. Hereinafter, a specific description will be given.

The main control unit 12 controls the operations of the transmission unit 14 and the reception unit 16 according to a set or selected pulse sequence. The main control unit 12 has a processor that operates a program, and functions as a transmission sequencer and a reception sequencer in the present embodiment. The main control unit 12 also has a function of controlling the reflected wave monitoring unit 30. The transmission unit 14 is an electronic circuit that generates a transmission pulse train, that is, a transmission signal. The transmission unit 14 has a power amplifier that amplifies the transmission signal. The amplified transmission signal is transmitted to the NMR measurement probe 24 via the transmission / reception changeover switch 18 and the selector 20.

The NMR measurement probe 24 is composed of an insertion portion and a base portion. The insertion portion is inserted into the bore of the static magnetic field generator. The base is the part that is located outside the bore. The NMR measurement probe 24 includes a detection circuit 26 that irradiates the measurement target nucleus with an electromagnetic wave having a resonance frequency and detects a FID signal from the measurement target nucleus. The detection circuit 26 has a plurality of electronic components such as a detection coil, a variable capacitor for tuning, and a variable capacitor for matching. The tuning variable capacitor and the matching capacitor are adjusted manually or automatically in the tuning performed prior to the NMR measurement or periodically. It is indicated by reference numerals 68 and 70 in FIG.

The detected FID signal is sent as an RF reception signal to the reception unit 16 via the selector 20 and the transmission / reception changeover switch 18. The receiving unit 16 is an electronic circuit that processes an RF reception signal, and includes an amplifier circuit, a frequency conversion circuit, an orthogonal detection circuit, a sampling circuit (ADC), and the like. The received data output from the receiving unit 16 is frequency-analyzed by the main control unit 12, whereby a spectrum is generated. The selector 20 has a routing (route selection) function. The selector 20 switches the path between the time of NMR measurement and the time of tuning.

Generally, the transmission unit 14 has a function of generating a plurality of transmission signals in parallel. Correspondingly, a plurality of transmission / reception changeover switches 18, 62 and a plurality of selectors 20, 64 may be provided in parallel. Similarly, a plurality of detection circuits 26 and 66 may be provided in parallel in the NMR measurement probe 24.

Next, the reflected wave monitoring unit 30 will be described. The reflected wave monitoring unit 30 functions during manual tuning or auto tuning.

The local processor 32 is composed of, for example, a programmatic microcomputer, and controls individual components in the reflected wave monitoring unit 30 according to a predetermined sequence. The local processor 32 functions as a reference level acquisition means and a standardization means, and in FIG. 1, these functions are represented as a reference level acquisition unit 48 and a standardization unit 50. The reference level acquisition unit 48 and the standardization unit 50 may each be configured by a dedicated processor, device, or the like. Further, other functions (for example, control function, graph generation function, communication function) of the local processor 32 may be configured by a dedicated processor, device, or the like.

A memory 52 and a touch panel 54 are connected to the local processor 32. A plurality of reference levels, which will be described later, are stored in the memory 52, and these are referred to in the standardization operation. The touch panel 54 is a user interface having a display function and an input function, and is composed of a display device such as an LCD and a touch sensor device. The reflected wave level is displayed as a numerical value or a graph on the touch panel 54. In the present embodiment, as will be described in detail later, the normalized (calibrated) reflected wave level can be displayed as the reflected wave information for tuning.

The transmission circuit 34 is an electronic circuit that generates a transmission signal (transmission wave) for tuning. The transmission circuit 34 has a function of generating a transmission signal having a designated frequency and a function of generating a transmission signal while repeatedly sweeping the frequency over a predetermined frequency range. The generated transmission signal is sent to the multiplexer 38 via the sensor 36. The transmission signal is sent to the connection destination circuit selected by the multiplexer 38, and a signal (reflected wave signal) representing the reflected wave from the connection destination circuit is sent to the reception circuit 46 via the multiplexer 38 and the sensor 36. Be done. The sensor 36 is composed of, for example, a directional coupler.

The receiving circuit 46 has an amplification function, a detection function (frequency conversion, complex conversion function), a sampling function, and the like. Reflected wave data indicating the reflected wave level (measured level before standardization) is sent from the receiving circuit 46 to the local processor 32.

The multiplexer 38 has eight channels (ports) CH1 to CH8 that are selectively selected in the illustrated configuration example. Further, the multiplexer 38 has a port to which the sensor 36 is connected. In the illustrated example, the detection circuit 26 to be tuned is connected to the channel CH1 via the selector 20. An open end circuit 40 is connected to channel CH7. The open end circuit 40 may literally be a circuit constituting the open end. As the open end circuit 40, an impedance mismatch configuration that causes total reflection or quasi-total reflection (strong reflection equivalent to total reflection) is adopted. A termination matching circuit 42 is connected to channel CH8. The termination matching circuit 42 is composed of a 50Ω resistor corresponding to the characteristic impedance of the transmission system of 50Ω. Alternatively, a resistor having another resistance value may be used. Alternatively, a variable resistor may be used. Further, the termination matching circuit 42 may be configured as an impedance matching circuit composed of a plurality of elements such as a resistor, a capacitor, and a coil. In any case, as the termination matching circuit 42, a circuit that causes non-reflection or a state equivalent thereto is provided. A detection circuit (tuning target) can be connected to each of channels CH2 to CH6, if necessary. For example, the detection circuit 66 may be connected to the channel CH2. Further, another measuring instrument may be connected to an empty channel.

The open end circuit 40 and the end matching circuit 42 are both reference circuits or dummy circuits that serve as a reflection source for obtaining a reference level. The multiplexer 38 selects the connection destination of the transmission circuit 34 and the reception circuit 46 (hereinafter, both are collectively referred to as “transmission / reception circuit”) from the circuit group including one or more detection circuits and one or more reference circuits. It is a selection circuit to be used. It should be noted that only one of the open end circuit 40 and the end matching circuit 42 may be provided. Alternatively, an additional reference circuit that produces an intermediate reflected wave level may be provided. In any case, one or a plurality of reference circuits are provided so that the standardization described in detail below can be appropriately performed.

The operation of the multiplexer 38 is controlled by the local processor 32. Therefore, the control signal 39 is given from the local processor 32 to the multiplexer 38. In the present embodiment, the multiplexer 38 selects the open end circuit 40, the termination matching circuit 42, and the detection circuit 26 in order as the connection destinations of the transmission / reception circuits at the time of tuning. Repeat such a series of selections as needed. According to the configuration shown in FIG. 1, when tuning the plurality of detection circuits 26 and 66 in sequence, the open end circuit 40 and the end matching circuit 42 can be shared, in other words, a plurality of reference levels can be shared. , You can get the advantage. If the characteristics of transmission paths and electronic circuits change over time, or if those characteristics may change with temperature changes, it is advisable to update multiple reference levels at any time or on a regular basis. desirable.

When the multiplexer 38 selects channel CH7, the transmission signal is sent to the open end circuit 40 via the multiplexer 38. Therefore, total reflection or quasi-total reflection occurs, that is, a reflected wave having a maximum or near level (first reference reflected wave) is generated. The signal representing the first reference reflected wave is sent to the receiving circuit 46 via the multiplexer 38 and the sensor 36. Based on the signal, the first reference level for normalization is acquired in the local processor 32.

When the multiplexer 38 selects channel CH8, the transmission signal is sent to the termination matching circuit 42 via the multiplexer 38. There, non-reflection or quasi-non-reflection occurs, that is, a reflected wave having a minimum or near level (second reference reflected wave) is generated. The signal representing the second reference reflected wave is sent to the receiving circuit 46 via the multiplexer 38 and the sensor 36. Based on the signal, the second reference level for normalization is acquired in the local processor 32.

When the multiplexer 38 selects the channel CH1, the transmission signal is sent to the detection circuit 26 via the multiplexer 38 and the selector 20. In the detection circuit 26, a reflected wave (actual reflected wave) having an intensity corresponding to the tuning state is generated. A signal indicating the actual reflected wave is sent to the receiving circuit 46 via the selector 20, the multiplexer 38 and the sensor 36. In the local processor 32, the actual reflected wave level is standardized and the standardization level is calculated based on the first reference level and the second reference level. The standardization level is displayed, or data 58 indicating the normalization level is sent to the auto-tuning device 56.

The operation of the selector 20 is controlled by the local processor 32, and therefore the control signal 43 is sent from the local processor 32 to the selector 20. The operation of the selector 20 may be controlled by the main control unit 12.

The reference level acquisition unit 48 in the local processor 32 is a module that acquires the first reference level and the second reference level described above. Data indicating the first reference level and the second reference level are stored in the memory 52. The normalization unit 50 in the local processor 32 applies a predetermined calculation formula for normalization to the actual reflected wave level based on the first reference level and the second reference level, and the normalization level is obtained as the calculation result. It is a module that finds. Incidentally, the local processor 32 has a function of obtaining a standardization level for a designated frequency and a function of obtaining a distribution (frequency characteristic) of the normalization level over a designated frequency range. When the former function is executed, the standardization level is displayed as a numerical value or as a bar graph. When the latter function is executed, the distribution of normalization level is displayed as a curve graph. The displayed contents change dynamically during the tuning process.

FIG. 2 shows the operation of the normalization unit shown in FIG. 1, that is, the standardization method. (A) shows the state before standardization, and (B) shows the state after standardization. The vertical axis shown in (A) and (B) represents the reflected wave level.

On the vertical axis shown in (A), the first reference level is represented as the maximum level L1 and the second reference level is represented as the minimum level L2. Basically, the measured level (actual reflected wave level) Lx is generated between the maximum level L1 and the minimum level L2.

On the vertical axis shown in (B), the maximum level L1 is associated with the maximum display value Lmax (see reference numeral 200). The minimum level L2 is associated with the display minimum value Lmin (see reference numeral 202). That is, the change range of the actual reflected wave level is scaled to fit the entire display range. In the present embodiment, the measured level Lx is converted to the normalized level Lx'based on the following equation (1) (see reference numeral 204).

Lx'= Lmax * (Lx-L2) / (L1-L2) ... (1)

In Eq. (1), Lmax is a scaling factor. Equation (1) assumes that the minimum display value Lmin is 0. If it is not 0, Lmax in the above equation (1) may be replaced with (Lmax-Lmin). The ratio (Lx-L2) / (L1-L2) in the above equation (1) corresponds to normalization or relativization.

By performing such a calculation, the measured level Lx is normalized by the maximum level L1 or the like, that is, the absolute value can be converted into a relative value, which is caused by, for example, a decrease in the transmitted wave level. It is possible to prevent or reduce the apparent decrease in the reflected wave level. In addition, it is possible to make maximum use of the finite display range. As a calculation formula for standardization, a formula other than the above formula (1) may be used. The normalization level Lx'is displayed or output after being logarithmically converted (see reference numeral 206) as necessary (see reference numeral 208). Depending on the tuning state, the measured level Lx is exceptionally set to a level beyond the range between the maximum level L1 and the minimum level L2 (at a place lower than the minimum level L2 or higher than the maximum level L1). It can occur. For example, when Lx is lower than L2, there is a problem that the calculation result of Eq. (1) becomes a negative value. As a method of dealing with such an inconvenience, a method of using only the maximum level L1 without using the minimum level L2, a method of providing a certain margin, and a method of using a complex transformation described later can be mentioned.

Here, the general flow of tuning will be described with reference to FIG. The reflected wave level for each frequency is shown as Graph 100. By repeating tuning and matching with reference to such a graph 100, the tuning state gradually improves, and the dip point 104 changes to the dip point 108 in the process. The dip point 108 is at a lower level than the dip point 104, and is in a position corresponding to the target frequency 109. Dip points are an important indicator in tuning, whether manual or automatic.

FIG. 4 shows problems that arise in the prior art. The graph 110 shows the reflected wave level (measured level) for each frequency. In the graph 110, a dip 110A represented by a broken line is generated on the low frequency side thereof. This is caused by factors such as the frequency characteristics of electronic circuits and transmission systems, and specifically, it is apparent attenuation due to a decrease in the level of the transmitted wave. Such an apparent dip 110A may occur with temperature changes. If such a dip 110A occurs, it may be mistaken for a regular dip. Even if such a misidentification does not occur, if tuning is performed based on the graph 110 including such a change, there is a possibility that correct tuning cannot be performed. On the other hand, in the above-mentioned actual form, since the normalization level is displayed, it is possible to eliminate or reduce such an apparent dip. For example, by standardization, the dip 110A can be corrected to the flat portion 110B. Therefore, a highly reliable graph can be provided. The same applies when the level of the reflected wave is provided as a numerical value.

FIG. 5 shows a specific configuration example of the receiving circuit 46 and the local processor 32 shown in FIG. Each function of the local processor 32 is realized by a program, but each function is shown as a block in FIG.

A signal representing the reflected wave (first reference reflected wave, second reference reflected wave or actual reflected wave) is amplified in the amplifier 72. The amplified signal is input to the orthogonal detector 74. The orthogonal detector 74 functions as a frequency converter and a complex converter. Specifically, the orthogonal detector 74 has two mixers 76, 78 and two LPF 80, 82 corresponding to a real part and an imaginary part. By the action of the orthogonal detector 74, the signal having the RF frequency is converted into a signal near DC, and at the same time, it is converted into a complex signal. The complex signal is converted into a digital complex signal by ADCs 84 and 86.

The reference level acquisition unit 48 acquires the first reference level (specifically, the first real part reference level and the first imaginary part reference level) based on the digital complex signal representing the first reference reflected wave. Further, the second reference level (specifically, the second real part reference level and the second imaginary part reference level) is acquired based on the digital complex signal representing the second reference reflected wave.

The normalization unit 50 calculates the normalization level from the digital complex signal representing the actual reflected wave based on the first reference level and the second reference level. Specifically, the standardizing unit 50 is composed of two standardizers 92 and 94 corresponding to a real number part and an imaginary number part. The normalizer 92 calculates a normalized real part from the real part of the digital complex signal representing the real reflected wave based on the first real part reference level and the second real part reference level. The normalizer 94 calculates a normalized imaginary part from the imaginary part of the digital complex signal representing the real reflected wave based on the first imaginary part reference level and the second imaginary part reference level. In standardization, the above equation (1) is applied individually to the real part and the imaginary part.

The arithmetic unit 96 calculates a standardized level expressed in a non-complex form from a standardized level expressed in a complex form. Specifically, the normalization level Lx'is calculated by the following equation (2).

Lx'= ((normalized real part) ² + (normalized imaginary part) ² ) ^1/2 ... (2)

When the calculation shown in the above equation (1) is performed as it is, if the measured level Lx is smaller than the minimum level L2, the normalization level becomes negative, but the above equation (2) is used on the premise of complex conversion. When applied, the standardization level will not be negative.

Next, an operation example (control content) of the configuration shown in FIG. 1 will be described. FIG. 6 shows an example of the first operation. In S10, the transmission frequency is set. In S12, the multiplexer selects an open-ended circuit as the connection destination of the transmission / reception circuit. In the selected state, transmission / reception is performed in S14, that is, the output of the transmitted wave and the detection of the reflected wave are performed, and the first reference level, that is, the maximum level L1 is acquired by the analysis of the reflected wave. In S16, the multiplexer selects a termination matching circuit as the connection destination of the transmission / reception circuit. In S18, transmission / reception is performed in the selected state, that is, the output of the transmitted wave and the detection of the reflected wave are performed, and the second reference level, that is, the minimum level L2 is acquired by the analysis of the reflected wave. In S20, the multiplexer selects the detection circuit as the connection destination of the transmission / reception circuit. In S22, transmission / reception is performed in the selected state, that is, transmission wave output and reflected wave detection are performed, and the measured level is detected by analysis of the reflected wave. Further, in S22, the measured level is converted into the standardized level based on the above equation (1). In S24, the standardization level is displayed as a numerical value, a bar graph, or the like. In S26, it is determined whether or not to continue the above processing.

In the above first operation example, the first reference level is acquired first, and then the second reference level is acquired, but the acquisition order may be reversed. Further, the measured level may be acquired first, and then the first reference level and the second reference level may be acquired later.

FIG. 7 shows an example of the second operation. In S30, the open-ended circuit is selected by the multiplexer. In S32, in the selected state, the maximum level (first reference level) is acquired for each frequency while sweeping the frequency over the designated frequency range. They constitute the maximum level frequency characteristic. When the first frequency sweep is completed, the steps after S34 are executed. That is, each process is executed in synchronization with or in conjunction with the frequency sweep. In S34, the terminal matching circuit is selected by the multiplexer. This circuit selection is made during frequency sweep. In S36, in the selected state, the minimum level (second reference level) is acquired for each frequency while sweeping the frequency over the designated frequency range. They constitute the minimum level frequency characteristic. When the second frequency sweep is completed, the steps after S38 are executed. In S38, the detection circuit is selected by the multiplexer. This circuit selection is made during frequency sweep. In S40, in the selected state, the measured level is acquired for each frequency while sweeping the frequency over the designated frequency range. They constitute the measured level frequency characteristics. When the third frequency sweep is completed, in S42, the normalized level frequency characteristic is calculated from the measured level frequency characteristic based on the maximum level frequency characteristic and the minimum level frequency characteristic. In S44, it is determined whether or not to repeat the above process.

In the second operation example, after acquiring three frequency characteristics, a normalization calculation is executed for each frequency. According to this, the number of operations of the multiplexer can be minimized, so that the calculation time can be significantly shortened. Incidentally, the time required for one frequency sweep is, for example, about several tens of ms to several hundreds of ms. In the frequency sweep, the transmission frequency is changed stepwise at a constant step.

FIG. 8 shows a third operation example. In the third operation example, the state in which the tuning operation is not performed is estimated, and two reference levels are acquired in that state. That is, the decrease in the measured level calculation rate is avoided during the actual tuning.

In S50, the transmission frequency is set. In S52, the open-ended circuit is selected by the multiplexer. In S54, the maximum level (first reference level) is acquired. In S56, the termination matching circuit is selected. In S57, the minimum level (second reference level) is acquired. In S58, the detection circuit is selected by the multiplexer. In S59, the measured level is detected, and the standardized level is calculated by normalizing the measured level based on the maximum level and the minimum level. In S60, the calculated standardization level is displayed. In S61, the counter M is initialized.

In S62, the detection of the measured level and the calculation of the normalization level are performed again, and in S64, the calculated standardization level is displayed again. In S66, the difference between the normalized level calculated last time and the normalized level calculated this time is calculated, and the difference is compared with the threshold value ΔX. If the difference is within the threshold ΔX, the process shifts to S68, and if not, the process shifts to S61. That is, when the difference is large and not stable, the counter M is reset and the steps after S62 are executed. In S68, the counter M indicating the duration of stabilization is incremented by one, and in S70, the counter M is subsequently compared to the threshold N. When the counter M reaches the threshold value N, the process shifts to S50 and the two reference values are acquired again. If the counter M is less than the threshold N, S62 is executed. The above process is continuously repeated until the end instruction is issued by the interrupt. For example, 100 is set as the threshold value N.

When the tuning operation is actually performed, the above difference often occurs, and if the difference exceeds the threshold value ΔX, the counter M is reset, so that the acquisition of the two reference levels is postponed. That is, the detection of the measured level is prioritized. Even if the difference is within the threshold value ΔX, if the state continues for a short time, the counter M does not reach the threshold value N, and the uptake of the two reference levels is also postponed. That is, the detection of the measured level is prioritized. When the counter M reaches the threshold value N, it is highly possible that the tuning operation has not actually been performed. In that case, the reacquisition of the two reference levels is executed. The local processor 32 functions as a control unit (control means) when executing each operation example.

A modified example will be described with reference to FIGS. 9 and 10. FIG. 9 shows a first modification. In the first modification, the selector 20 and the multiplexer 38 shown in FIG. 1 are integrated. That is, a composite multiplexer 152 is provided.

More specifically, the reflected wave monitoring unit 150 includes a signal processing module 156, a multiplexer 152, an open end circuit 162, and a termination matching circuit 164. The multiplexer 152 has two channels (ports) CH00 and CH01 that are selectively used on the transmitter / receiver side. Channel CH00 is connected to the spectroscope main body 154 (specifically, a transmitting unit and a receiving unit). Channel CH01 is connected to the signal processing module 156. The signal processing module 156 includes a transmission / reception circuit, a local processor having an acquisition unit and a standardization unit, and the like. A control signal 157 is sent from the signal processing module 156 to the multiplexer 152.

The multiplexer 152 has eight channels (ports) CH1 to CH8 that are selectively used on the circuit group side. Similar to the configuration example shown in FIG. 1, the detection circuit 160 in the NMR measurement probe 158 is connected to the channel CH1. An open end circuit 162 is connected to channel CH7. A termination matching circuit 164 is connected to channel CH8. Channels CH2 to CH6 are used as needed. As described above, the multiplexer has a 2 × 8 routing function.

According to the first modification, the number of parts can be reduced as compared with the configuration example shown in FIG. Further, from a physical and electrical point of view, the configuration from the multiplexer 152 to the open end circuit 162 and the termination matching circuit 164 is close to the configuration from the multiplexer 152 to the detection circuit 160, so that a more accurate reference level is obtained. It is possible.

A second modification is shown in FIG. The reflected wave monitoring unit 168 has a multiplexer 170. The configuration on the reflection side is the same as that shown in FIG. The spectrometer main body 174 includes a transmission unit 176, a reception unit 178, and a calculation unit 180, which function during normal NMR measurement and also during tuning. That is, at the time of tuning, the transmission unit 176 generates a transmission signal for tuning. The receiving unit 178 processes a signal representing a reflected wave (first reference reflected wave, second reference reflected wave, or actual reflected wave), and passes the received data obtained thereby to the calculation unit 180. The calculation unit 180 functions as a reference level acquisition unit and a standardization unit. Specifically, the calculation unit 180 acquires the first reference level and the second reference level, and converts the measured level into the standardized level based on them. The spectrometer body 174 controls the operation of the multiplexer 170. According to the second modification, although the configuration of the spectroscope main body 174 becomes complicated, the configuration can be simplified as a whole system.

According to the above configuration, it is less likely to be affected by the frequency characteristics of the device used at the time of tuning and the transmission path. In particular, even when the level is lowered in the transmission process of the transmitted wave and the measured level is apparently lowered due to this, the normalized level can be displayed as the reflected wave information, so that correct tuning can be performed. Further, even if the measured level changes regardless of the tuning state due to a temperature change or the like in the tuning process, the normalized level can be displayed as reflected wave information, so that correct tuning can be performed. As described above, according to the embodiment, it is possible to provide an extremely practical reflected wave monitoring technique.

10 Spectrometer body, 20 selector, 24 NMR measurement probe, 26 detection circuit, 30 reflected wave monitoring unit, 32 local processor, 34 transmitter circuit, 38 multiplexer, 40 open end circuit, 42 termination matching circuit, 46 receiver circuit, 48 reference Level acquisition department, 50 standardization department.

Claims (10)

A transmitter / receiver circuit that generates a transmitted wave for tuning and receives a reflected wave,
An NMM measurement probe with an NMR detection circuit and
To the transceiver circuit, a selection circuit for connecting a circuit selected from among circuit group including the NMR detection circuit and the reference circuit,
It has an acquisition means for acquiring the level of the reference reflected wave received in the selected state of the reference circuit as the reference level, and the fact that the NMR detection circuit is received in the selected state based on the reference level. An arithmetic means for calculating the standardization level by standardizing the level of the reflected wave, and
Only including,
The transmission / reception circuit generates a transmission wave while performing frequency sweep,
The selection circuit selects a circuit from the circuit group according to the frequency sweep cycle, whereby circuit selection is performed between frequency sweeps.
The calculation means is
A means for generating a reference level frequency characteristic indicating a change in the reference level caused by the frequency sweep, and
A means for generating an actually measured level frequency characteristic indicating a change in the level of the actual reflected wave caused by the frequency sweep, and a means for generating the measured level frequency characteristic.
By standardizing the measured level frequency characteristic based on the reference level frequency characteristic, a means for generating a standardized level frequency characteristic representing a standardized level for each frequency, and a means for generating the standardized level frequency characteristic.
including,
An NMR measuring device characterized by the above. In the apparatus according to claim 1,
The circuit group includes a first reference circuit that causes total reflection or quasi-total reflection as the reference circuit.
The acquisition means acquires the level of the reference reflected wave received with the first reference circuit selected as the first reference level.
An NMR measuring device characterized by the above. In the apparatus according to claim 1,
The circuit group includes a second reference circuit that causes non-reflection or quasi-non-reflection as the reference circuit.
The acquisition means acquires the level of the reference reflected wave received with the second reference circuit selected as the second reference level.
An NMR measuring device characterized by the above. In the apparatus according to claim 1,
The circuit group includes, as the reference circuit, a first reference circuit that causes total reflection or quasi-total reflection, and a second reference circuit that causes non-reflection or quasi-non-reflection.
The acquisition means acquires the level of the reference reflected wave received with the first reference circuit selected as the first reference level, and the reference reflected wave received with the second reference circuit selected. Level is taken as the second reference level,
The calculation means calculates the normalization level based on the ratio represented by (actual reflected wave level-second reference level) / (first reference level-second reference level).
An NMR measuring device characterized by the above. In the apparatus according to claim 2,
The first reference circuit is an open end circuit.
An NMR measuring device characterized by the above. In the apparatus according to claim 3,
The second reference circuit is a terminal circuit having an impedance matching action.
An NMR measuring device characterized by the above. In the apparatus according to claim 1,
A means for displaying the standardized level frequency characteristic as a curve graph is included.
An NMR measuring device characterized by the above. In the apparatus according to claim 1,
A complex conversion circuit that converts a signal representing the level of the reference reflected wave into a reference level signal in a complex format and a signal representing the level of the actual reflected wave into a measured level signal in a complex format is included.
The acquisition means acquires the real part reference level and the imaginary part reference level as the reference level based on the complex form reference level signal.
The arithmetic means normalizes the measured level signal in the complex form based on the real part reference level and the imaginary part reference level.
An NMR measuring device characterized by the above. Against receiving circuit for receiving the generated and reflected wave transmission waves for tuning while frequency sweep, NMR detection circuit in the NMR measurement probe, and a circuit selected from among circuit group including the reference circuit In the step of connecting, a circuit is selected from the circuit group according to the frequency sweep cycle, and the circuit selection is performed between the frequency sweeps .
A step of acquiring the level of the reference reflected wave received with the reference circuit selected as a reference level, and a step of generating a reference level frequency characteristic indicating a change in the reference level caused by the frequency sweep. ,
A means for acquiring the level of the actual reflected wave received with the NMR detection circuit selected, and generating an actually measured level frequency characteristic indicating a change in the level of the actual reflected wave caused by the frequency sweep. When,
A process of calculating a standardized level frequency characteristic representing a standardized level for each frequency by standardizing the measured level frequency characteristic based on the reference level frequency characteristic.
A reflected wave monitoring method comprising. In the method according to claim 9.
Further, the step of determining the necessity of reacquisition of the reference level based on the stability of the standardization level is included.
A reflected wave monitoring method characterized by this.

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