Real-time self-checking system applied to low-field nuclear magnetic equipment

Abstract

The invention relates to the technical field of nuclear magnetic resonance, in particular to a real-time self-checking system applied to low-field nuclear magnetic equipment, in the system, a control end of a field programmable gate array is respectively connected to a radio frequency power amplifier and each radio frequency switch; the direct digital synthesizer is connected to the probe through the first coupler, the radio frequency power amplifier and the second coupler in sequence, and the coupling end of the first coupler is connected to the first radio frequency switch; a first radio frequency end of the first radio frequency switch is connected to the first analog-to-digital converter, a second radio frequency end of the first radio frequency switch is connected with a second radio frequency end of the second radio frequency switch, a first radio frequency end of the second radio frequency switch is connected to the radio frequency power amplifier, and a common end of the second radio frequency switch is connected to the first analog-to-digital converter through the preamplifier; the second coupler is connected to the second analog-to-digital converter through the third radio frequency switch. The system is simple in structure, can monitor the low-field nuclear magnetic equipment in real time, and can accurately position a fault source.

Description

Technical Field

[0001] The present invention relates to the technical field of nuclear magnetic resonance, and particularly relates to a real-time self-checking system applied to low-field nuclear magnetic resonance equipment. Background Art

[0002] As a multi-disciplinary cross-analysis method, low-field nuclear magnetic resonance (LF-NMR) technology has shown significant application value in the fields of biomedical detection, industrial material characterization, and geological core pore structure analysis. Its non-destructive quantitative analysis ability provides key data support for quality control and scientific research.

[0003] However, when the low-field nuclear magnetic resonance equipment operates for a long time, the working states of core components such as radio frequency power amplifiers, pre-amplifiers, radio frequency coils, and magnets are prone to change, resulting in a decrease in the reliability of detection data and affecting the accuracy of analysis results. Therefore, the real-time self-checking of low-field nuclear magnetic resonance equipment is crucial. In the prior art, most nuclear magnetic resonance equipment is not equipped with a real-time self-checking system and only performs detection when starting up or reaching a fixed cycle, and cannot provide component status data at each sampling; although some equipment is equipped with a self-checking system, its structure is complex, the cost is high, and the source of the fault cannot be accurately located, making it difficult to be widely applied.

[0004] Therefore, there is an urgent need to develop a real-time self-checking system for low-field nuclear magnetic resonance equipment that can monitor the status of core components in real time and accurately locate the source of faults. Summary of the Invention

[0005] In view of this, the present invention provides a real-time self-checking system applied to low-field nuclear magnetic resonance equipment to solve the problems that existing low-field nuclear magnetic resonance equipment lacks real-time monitoring ability, and some self-checking systems have complex structures, high costs, and cannot accurately locate the source of faults.

[0006] The present invention provides a real-time self-checking system applied to low-field nuclear magnetic resonance equipment, and the system includes: a nuclear magnetic resonance analysis structure, a first coupler, a second coupler, and three radio frequency switches; the nuclear magnetic resonance analysis structure includes a spectrometer unit, a radio frequency power amplifier, a pre-amplifier, and a probe; the spectrometer unit includes a field programmable gate array, a direct digital synthesizer, a first analog-to-digital converter, and a second analog-to-digital converter; The control ends of the field programmable gate array are respectively connected to the gate control end of the radio frequency power amplifier and the control ends of each radio frequency switch; The output end of the direct digital synthesizer is connected to the input end of the first coupler. The output end of the first coupler is sequentially connected to the signal interaction end of the probe through the radio frequency power amplifier and the second coupler. The coupling end of the first coupler is connected to the common end of the first radio frequency switch; the output end of the direct digital synthesizer is used as the starting end of the self-checking signal; The first RF terminal of the first RF switch is connected to the input terminal of the first analog-to-digital converter. The second RF terminal of the first RF switch is connected to the second RF terminal of the second RF switch. The first RF terminal of the second RF switch is connected to the output terminal of the RF power amplifier. The common terminal of the second RF switch is connected to the input terminal of the first analog-to-digital converter through the preamplifier. Both the forward terminal and the reverse terminal of the second coupler are connected to the input terminal of the second analog-to-digital converter through the third RF switch.

[0007] In an alternative embodiment, the first coupler is configured to couple out a split signal from the output signal of the direct digital synthesizer for spectrometer unit self-check and preamplifier self-check. The second coupler is configured to separate the forward signal output by the RF power amplifier from the reverse reflection signal of the probe for RF power amplifier self-check and probe self-check.

[0008] In an alternative embodiment, the first RF switch, the second RF switch, and the third RF switch are all single-pole double-throw RF switches. The single-pole double-throw RF switch is configured to switch the connection path between the common terminal and the RF terminal of the single-pole double-throw RF switch based on the control signal sent from the control terminal of the field programmable gate array to switch the signal flow direction.

[0009] In an alternative embodiment, the nuclear magnetic resonance analysis structure further includes a transmit / receive switch. The output terminal of the RF power amplifier is connected to the transmit end of the transmit / receive switch. The receive end of the transmit / receive switch is connected to the first RF terminal of the second RF switch. The common terminal of the transmit / receive switch is connected to the signal interaction terminal of the probe through the second coupler.

[0010] In an alternative embodiment, the forward terminal of the second coupler is connected to the first RF terminal of the third RF switch, and the reverse terminal of the second coupler is connected to the second RF terminal of the third RF switch. The common terminal of the third RF switch is connected to the input terminal of the second analog-to-digital converter.

[0011] In an alternative embodiment, during the spectrometer unit self-check, the field programmable gate array is configured to control the gate terminal of the RF power amplifier to be at a low level through the first control terminal, control the first RF switch to switch to the first RF terminal through the second control terminal, and control the second RF switch to switch to the second RF terminal through the third control terminal. The output terminal of the first analog-to-digital converter is configured to output the detection signal of the spectrometer unit self-check.

[0012] In an alternative embodiment, when the preamplifier performs self-check, the field programmable gate array is configured to control the gate terminal of the radio frequency power amplifier to be at a low level through the first control terminal, control the first radio frequency switch to switch to the second radio frequency terminal through the second control terminal, and control the second radio frequency switch to switch to the second radio frequency terminal through the third control terminal; the output terminal of the first analog-to-digital converter is configured to output a detection signal for the self-check of the preamplifier.

[0013] In an alternative embodiment, when the spectrometer unit performs self-check and the preamplifier performs self-check, the field programmable gate array is further configured to control the third radio frequency switch to switch to the first radio frequency terminal or the second radio frequency terminal through the fourth control terminal.

[0014] In an alternative embodiment, when the radio frequency power amplifier performs self-check, the field programmable gate array is configured to control the gate terminal of the radio frequency power amplifier to be at a high level through the first control terminal, control the first radio frequency switch to switch to the second radio frequency terminal through the second control terminal, control the second radio frequency switch to switch to the first radio frequency terminal through the third control terminal, and control the third radio frequency switch to switch to the first radio frequency terminal through the fourth control terminal; the output terminal of the second analog-to-digital converter is configured to output a detection signal for the self-check of the radio frequency power amplifier.

[0015] In an alternative embodiment, when the probe performs self-check, the field programmable gate array is configured to control the gate terminal of the radio frequency power amplifier to be at a high level through the first control terminal, control the first radio frequency switch to switch to the second radio frequency terminal through the second control terminal, control the second radio frequency switch to switch to the first radio frequency terminal through the third control terminal, and control the third radio frequency switch to switch to the second radio frequency terminal through the fourth control terminal; the output terminal of the second analog-to-digital converter is configured to output a detection signal for the self-check of the probe.

[0016] The technical solution provided by the present invention may include the following beneficial effects: Based on the original low-field nuclear magnetic resonance analysis instrument (i.e., nuclear magnetic resonance analysis structure), the present invention only needs to add a first coupler, a second coupler and three radio frequency switches, without reconstructing the original system architecture, and can build a full-link self-checking ability on the basis of the original equipment, realizing self-check of the spectrometer unit, radio frequency power amplifier, preamplifier and probe. The structure is simple and the hardware cost is reduced. Moreover, in terms of equipment status monitoring and fault location, the present invention realizes real-time self-check of different components of the low-field nuclear magnetic resonance equipment through precise control of each radio frequency switch by the field programmable gate array. Once a component fails, the fault source can be quickly located, reducing the equipment downtime and maintenance cost, and improving the reliability and availability of the equipment. Description of the Drawings

[0017] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for use in the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0018] Figure 1 is a schematic structural diagram of a real-time self-checking system applied to a low-field nuclear magnetic resonance device according to an embodiment of the present invention; Figure 2 is a schematic diagram of a spectrometer unit self-checking sequence according to an embodiment of the present invention; Figure 3 is a schematic diagram of a preamplifier self-checking sequence according to an embodiment of the present invention; Figure 4 is a schematic diagram of a radio frequency power amplifier self-checking sequence according to an embodiment of the present invention; Figure 5 is a schematic diagram of a probe self-checking sequence according to an embodiment of the present invention; Figure 6 is a schematic diagram of the relationship between the T2 peak area and the slice selection position before and after receiver gain correction according to an embodiment of the present invention. Specific Embodiments

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

[0020] According to an embodiment of the present invention, an embodiment of a real-time self-checking system applied to a low-field nuclear magnetic resonance device is provided. Figure 1 is a schematic structural diagram of a real-time self-checking system applied to a low-field nuclear magnetic resonance device according to an embodiment of the present invention, as Figure 1 shown. The system includes: a nuclear magnetic resonance analysis structure, a first coupler, a second coupler, and three radio frequency switches. The three radio frequency switches are respectively Figure 1 the first radio frequency switch in Figure 1 (i.e., SPDT1 in Figure 1 ), the second radio frequency switch (i.e., SPDT2 in Figure 1 ), and the third radio frequency switch (i.e., SPDT3 in Figure 1 ); the nuclear magnetic resonance analysis structure includes a spectrometer unit, a radio frequency power amplifier, a preamplifier, and a probe; the spectrometer unit includes a field programmable gate array (i.e., Figure 1the FPGA therein), the direct digital synthesizer (i.e., Figure 1 the DDS therein), the first analog-to-digital converter (i.e., Figure 1 the ADC1 therein), and the second analog-to-digital converter (i.e., Figure 1 the ADC2 therein); The control terminals of the field programmable gate array are respectively connected to the gate control terminal of the radio frequency power amplifier and the control terminals of each radio frequency switch; specifically: the first control terminal of the field programmable gate array (i.e., Figure 1 the GATE1 therein) is connected to the gate control terminal of the radio frequency power amplifier (i.e., Figure 1 the GATE therein), the second control terminal of the field programmable gate array (i.e., Figure 1 the GATE2 therein) is connected to the control terminal of the first radio frequency switch, the third control terminal of the field programmable gate array (i.e., Figure 1 the GATE3 therein) is connected to the control terminal of the second radio frequency switch, and the fourth control terminal of the field programmable gate array (i.e., Figure 1 the GATE4 therein) is connected to the control terminal of the third radio frequency switch.

[0021] The output terminal of the direct digital synthesizer (the output terminal of the direct digital synthesizer serves as the starting end of the self-check signal) is connected to the input terminal (IN) of the first coupler, and the output terminal (OUT) of the first coupler is sequentially connected to the signal interaction terminal of the probe through the radio frequency power amplifier and the second coupler; specifically: the output terminal (OUT) of the first coupler is connected to the input terminal (IN) of the radio frequency power amplifier, the output terminal (OUT) of the radio frequency power amplifier is connected to the input terminal (IN) of the second coupler, and the output terminal (OUT) of the second coupler is connected to the signal interaction terminal of the probe.

[0022] The coupling terminal (COUP) of the first coupler is connected to the common terminal of the first radio frequency switch; the first radio frequency terminal (port 0) of the first radio frequency switch is connected to the input terminal of the first analog-to-digital converter, the second radio frequency terminal (port 1) of the first radio frequency switch is connected to the second radio frequency terminal (port 1) of the second radio frequency switch, the first radio frequency terminal (port 0) of the second radio frequency switch is connected to the output terminal (OUT) of the radio frequency power amplifier, and the common terminal of the second radio frequency switch is connected to the input terminal of the first analog-to-digital converter through the preamplifier; specifically: the common terminal of the second radio frequency switch is connected to the input terminal of the preamplifier, and the output terminal of the preamplifier is connected to the input terminal of the first analog-to-digital converter.

[0023] Both the forward terminal (FOR) and the reverse terminal (REV) of the second coupler are connected to the input terminal of the second analog-to-digital converter through the third radio frequency switch.

[0024] Further, the field programmable gate array is the control center of the entire system, responsible for outputting control signals to control the switching state of the radio frequency power amplifier and the switching of each radio frequency switch. The direct digital synthesizer is used to generate radio frequency signals with high precision and high stability, serving as the excitation signal and the self-test signal source. The first analog-to-digital converter is used to collect the self-test signals of the spectrometer unit and the preamplifier, converting them into digital signals for analysis by the field programmable gate array; the second analog-to-digital converter is used to collect the self-test signals of the radio frequency power amplifier and the probe, and analyze the forward and reverse powers. The radio frequency power amplifier is used to amplify the radio frequency signals output by the direct digital synthesizer, driving the probe to generate nuclear magnetic resonance signals. The preamplifier is used to amplify the nuclear magnetic resonance signals returned by the probe and input them to the first analog-to-digital converter for digital processing. The probe is the part that directly contacts the sample, used to emit radio frequency signals to the sample and receive the response signals generated by the sample.

[0025] In an alternative embodiment, the first coupler can be a low-power coupler, and the second coupler can be a dual-channel directional coupler; The first coupler is used to couple out a split signal from the output signal of the direct digital synthesizer for self-testing of the spectrometer unit and the preamplifier; that is, to extract a small part of the power from the output signal of the direct digital synthesizer for self-testing of the spectrometer unit and the preamplifier, and the main signal continues to be transmitted to the power amplifier; The second coupler is used to separate the forward signal output by the radio frequency power amplifier from the reverse reflection signal of the probe for self-testing of the radio frequency power amplifier and the probe; that is, to separate the forward output signal of the radio frequency power amplifier from the reverse reflection signal of the probe, which are respectively used for self-testing of the radio frequency power amplifier and the probe.

[0026] In an alternative embodiment, the first radio frequency switch, the second radio frequency switch, and the third radio frequency switch are all single-pole double-throw radio frequency switches; The single-pole double-throw radio frequency switch is used to switch the connection path between the common terminal and the radio frequency terminal of the single-pole double-throw radio frequency switch based on the control signal sent from the control terminal of the field programmable gate array to switch the signal flow direction.

[0027] Further, by switching the connection between the common terminal and different radio frequency terminals, the first radio frequency switch can direct the coupled signal to different paths for self-testing of the spectrometer unit or the preamplifier. By switching the connection between the common terminal and different radio frequency terminals, the second radio frequency switch can control whether the signal passes through the preamplifier to achieve self-testing of the preamplifier. By switching the connection between the common terminal and different radio frequency terminals, the third radio frequency switch can collect the forward signal and the reverse signal respectively to achieve self-testing of the radio frequency power amplifier and the probe.

[0028] In an alternative embodiment, the nuclear magnetic resonance analysis structure further includes a transmit / receive switch (i.e., the Figure 1 T / X switch in The output terminal (OUT) of the RF power amplifier is connected to the transmit terminal (T) of the transmit / receive switch; the receive terminal (X) of the transmit / receive switch is connected to the first RF terminal (port 0) of the second RF switch; the common terminal (T / X) of the transmit / receive switch is connected to the signal interaction terminal of the probe through the second coupler. Specifically, the common terminal (T / X) of the transmit / receive switch is connected to the input terminal (IN) of the second coupler, and the output terminal (OUT) of the second coupler is connected to the signal interaction terminal of the probe.

[0029] Furthermore, the transmit / receive switch is used to switch between the signal transmission and signal reception modes; in the signal transmission mode, the transmit / receive switch transmits the RF signal output by the RF power amplifier to the probe so that the probe can transmit signals to the sample. In the signal reception mode, the transmit / receive switch transmits the nuclear magnetic resonance signal received by the probe to the second RF switch, and then it is amplified by the preamplifier and undergoes subsequent processing. In the transmit mode, the common terminal (T / X) of the transmit / receive switch is connected to the transmit terminal (T), and the signal output by the RF power amplifier sequentially passes through the transmit / receive switch and the second coupler, and finally is transmitted to the signal interaction terminal of the probe and emitted by the probe. In the receive mode, the signal received by the probe is transmitted to the common terminal (T / X) of the transmit / receive switch through the second coupler. At this time, the common terminal (T / X) of the transmit / receive switch is connected to the receive terminal (X), and the signal is output from the receive terminal (X), passes through the second RF switch and is transmitted to the preamplifier for amplification, and then is converted into a digital signal by the first analog-to-digital converter for subsequent processing and analysis.

[0030] In an alternative embodiment, the forward terminal (FOR) of the second coupler is connected to the first RF terminal (port 0) of the third RF switch, and the reverse terminal (REV) of the second coupler is connected to the second RF terminal (port 1) of the third RF switch; the common terminal of the third RF switch is connected to the input terminal of the second analog-to-digital converter.

[0031] In an alternative embodiment, during the self-check of the spectrometer unit, the field programmable gate array is used to control the gate terminal of the RF power amplifier to be at a low level through the first control terminal, control the first RF switch to switch to the first RF terminal through the second control terminal, and control the second RF switch to switch to the second RF terminal through the third control terminal; the output terminal of the first analog-to-digital converter is used to output the detection signal for the self-check of the spectrometer unit.

[0032] Furthermore, the principle of self-checking of the spectrometer unit is as follows: When the direct digital synthesizer and the analog-to-digital converter inside the spectrometer unit perform self-checking, the field programmable gate array outputs a control signal to control the first radio frequency switch to switch to the first radio frequency terminal (port 0), and the second radio frequency switch to switch to the second radio frequency terminal (port 1). The third radio frequency switch can switch to the second radio frequency terminal (port 1) or the first radio frequency terminal (port 0). At this time, the gate control of the radio frequency power amplifier is at a low level (0V), and the radio frequency power amplifier is turned off. A part of the power is coupled out by the first coupler from the signal sent by the direct digital synthesizer, enters the first analog-to-digital converter via the first radio frequency switch, and the detection signal (S1) for self-checking of the spectrometer unit is obtained, realizing spectrometer detection. Please refer to Figure 2 the schematic diagram of the self-checking sequence of the spectrometer unit shown in Figure 2 In Figure 2 , the direct digital synthesizer (DDS) sends out a radio frequency signal as the excitation signal and the self-checking signal source; GATE1 is set low (to turn off the radio frequency power amplifier); GATE2 is set low (to switch the first radio frequency switch to port 0); GATE3 is set high (to switch the second radio frequency switch to port 1); GATE4 is arbitrary (the state of the third radio frequency switch does not affect the spectrometer self-checking).

[0033] That is to say, during the self-checking process of the spectrometer unit of the low-field nuclear magnetic resonance device, the field programmable gate array makes the system enter a specific detection state through control signals: First, the gate control terminal of the radio frequency power amplifier is set to a low level to turn off the power amplifier and prevent the self-checking signal from entering the subsequent link; then control the first radio frequency switch to switch to the first radio frequency terminal (port 0) and the second radio frequency switch to switch to the second radio frequency terminal (port 1) to form an independent detection path from the direct digital synthesizer through the coupling terminal of the first coupler, the first radio frequency switch to the first analog-to-digital converter; at this time, the signal sent by the direct digital synthesizer directly enters the first analog-to-digital converter after coupling, and the detection signal (S1) output by the first analog-to-digital converter only reflects the output characteristics of the direct digital synthesizer (such as frequency accuracy, amplitude stability) and the sampling performance of the first analog-to-digital converter (such as noise level, linearity), realizing the pure internal loop detection of the core components of the spectrometer unit, excluding the interference of the back-end link, and ensuring the detection accuracy.

[0034] In an optional implementation manner, when the preamplifier performs self-checking, the field programmable gate array is used to control the gate control terminal of the radio frequency power amplifier to be at a low level through the first control terminal, control the first radio frequency switch to switch to the second radio frequency terminal through the second control terminal, and control the second radio frequency switch to switch to the second radio frequency terminal through the third control terminal; the output terminal of the first analog-to-digital converter is used to output the detection signal for self-checking of the preamplifier.

[0035] Further, the principle of the preamplifier self-test is as follows: When the preamplifier is self-tested, the first RF switch is switched to the second RF terminal (port 1), the second RF switch is switched to the second RF terminal (port 1), and the third RF switch can be switched to the second RF terminal (port 1) or the first RF terminal (port 0). At this time, the gate control of the RF power amplifier is at a low level (0V), and the RF power amplifier is turned off. A part of the power is coupled out by the first coupler from the signal emitted by the direct digital synthesizer, amplified by the preamplifier after passing through the first RF switch and the second RF switch, and then enters the first analog-to-digital converter to obtain the detection signal (S2) of the preamplifier self-test, realizing the preamplifier detection. Please refer to Figure 3 the schematic diagram of the preamplifier self-test sequence shown in Figure 3 In the figure, the direct digital synthesizer (DDS) emits an RF signal as the excitation signal and the self-test signal source; GATE1 is set low (turn off the RF power amplifier); GATE2 is set high (switch the first RF switch to port 1); GATE3 is set high (switch the second RF switch to port 1); GATE4 is arbitrary (the state of the third RF switch does not affect the preamplifier self-test).

[0036] That is to say, during the self-test of the preamplifier in the low-field nuclear magnetic resonance equipment, the field programmable gate array makes the system enter a specific detection state through control signals. First, the gate control terminal of the RF power amplifier is set to a low level to turn off the power amplifier and prevent the self-test signal from entering the subsequent link; then, it controls the first RF switch to switch to the second RF terminal (port 1) and the second RF switch to switch to the second RF terminal (port 1), forming a detection path from the direct digital synthesizer through the coupling terminal of the first coupler, the first RF switch, the second RF switch to the preamplifier, and then to the first analog-to-digital converter. At this time, the signal emitted by the direct digital synthesizer enters the preamplifier after being coupled and transmitted through the switch, and the amplified signal is sampled by the first analog-to-digital converter. The detection signal (S2) output by the first analog-to-digital converter reflects the performance indicators such as the gain and noise figure of the preamplifier, realizing the independent detection of the preamplifier. This self-test mechanism quickly verifies the performance of the preamplifier through hardware path reconstruction without affecting other components, providing a reliable guarantee for the high-precision detection of the low-field nuclear magnetic resonance equipment.

[0037] In an optional implementation manner, when the spectrometer unit is self-tested and the preamplifier is self-tested, the field programmable gate array is further configured to control the third RF switch to switch to the first RF terminal or the second RF terminal through the fourth control terminal.

[0038] In an alternative embodiment, during the self-test of the RF power amplifier, the field programmable gate array is used to control the gate terminal of the RF power amplifier to a high level through the first control terminal, control the first RF switch to switch to the second RF terminal through the second control terminal, control the second RF switch to switch to the first RF terminal through the third control terminal, and control the third RF switch to switch to the first RF terminal through the fourth control terminal; the output terminal of the second analog-to-digital converter is used to output the detection signal of the self-test of the RF power amplifier.

[0039] Furthermore, the principle of the self-test of the RF power amplifier is as follows: During the self-test of the RF power amplifier, the first RF switch switches to the second RF terminal (port 1), the second RF switch switches to the first RF terminal (port 0), and the third RF switch switches to the first RF terminal (port 0). At this time, the gate control of the RF power amplifier is at a high level (1V), and the RF power amplifier is turned on. The signal output by the RF power amplifier passes through the second coupler, and a part of the forward signal (S3) is separated and enters the second analog-to-digital converter to achieve the self-test of the RF power amplifier. Please refer to Figure 4 the schematic diagram of the self-test sequence of the RF power amplifier shown, Figure 4 in which, the direct digital synthesizer (DDS) emits an RF signal as the excitation signal and the self-test signal source; GATE1 is set high (turn on the RF power amplifier); GATE2 is set high (switch the first RF switch to port 1); GATE3 is set low (switch the second RF switch to port 0); GATE4 is arbitrary (the state of the third RF switch does not affect the self-test of the RF power amplifier).

[0040] That is to say, during the self-test process of the RF power amplifier of the low-field nuclear magnetic resonance equipment, the field programmable gate array enables the system to enter a specific detection state through control signals: first, set the gate terminal of the RF power amplifier to a high level to turn on the power amplifier and allow the signal output by the direct digital synthesizer to be amplified by the power amplifier; then control the first RF switch to switch to the second RF terminal (port 1) to direct the signal of the direct digital synthesizer to the input terminal of the power amplifier; control the second RF switch to switch to the first RF terminal (port 0) to connect the output signal of the power amplifier to the second coupler; control the third RF switch to switch to the first RF terminal (port 0) to direct the forward signal separated by the second coupler to the second analog-to-digital converter; at this time, the signal emitted by the direct digital synthesizer is amplified by the power amplifier, and the forward signal (S3) separated by the second coupler is sampled by the second analog-to-digital converter. The detection signal output by the second analog-to-digital converter reflects the performance indicators such as the output power, stability, and linearity of the power amplifier, realizing the independent detection of the power amplifier.

[0041] In an alternative embodiment, during the self-test of the probe, the field programmable gate array is used to control the gate terminal of the radio frequency power amplifier to a high level through the first control terminal, control the first radio frequency switch to switch to the second radio frequency terminal through the second control terminal, control the second radio frequency switch to switch to the first radio frequency terminal through the third control terminal, and control the third radio frequency switch to switch to the second radio frequency terminal through the fourth control terminal; the output terminal of the second analog-to-digital converter is used to output the detection signal of the probe self-test.

[0042] Further, the principle of the probe self-test is as follows: during the probe self-test, the first radio frequency switch switches to the second radio frequency terminal (port 1), the second radio frequency switch switches to the first radio frequency terminal (port 0), and the third radio frequency switch switches to the second radio frequency terminal (port 1). At this time, the gate control of the radio frequency power amplifier is at a high level (1V), and the radio frequency power amplifier is turned on. The signal output by the radio frequency power amplifier passes through the second coupler, and a part of the reverse signal (S4) is separated and enters the second analog-to-digital converter. By comparing the reverse signal (S4) with the forward signal (S3) detected during the self-test of the radio frequency power amplifier, the reflection coefficient of the probe is obtained, and the probe detection is realized. Please refer to Figure 5 the schematic diagram of the probe self-test sequence shown, Figure 5 in which the direct digital synthesizer (DDS) emits a radio frequency signal as the excitation signal and the self-test signal source; GATE1 is set high (turn on the radio frequency power amplifier); GATE2 is set low (switch the first radio frequency switch to port 0); GATE3 is set high (switch the second radio frequency switch to port 1); GATE4 is set high (switch the third radio frequency switch to port 1).

[0043] That is to say, during the self-check of the probe of the low-field nuclear magnetic resonance device, the field-programmable gate array enables the system to enter a specific detection state through control signals: First, the gate terminal of the radio frequency power amplifier is set to a high level to turn on the power amplifier, allowing the signal output by the direct digital synthesizer to be amplified by the power amplifier; then, the first radio frequency switch is controlled to switch to the second radio frequency terminal (port 1) to direct the signal of the direct digital synthesizer to the input terminal of the power amplifier; the second radio frequency switch is controlled to switch to the first radio frequency terminal (port 0) to connect the output signal of the power amplifier to the second coupler; the third radio frequency switch is controlled to switch to the second radio frequency terminal (port 1) to direct the reverse signal (from the probe reflection) separated by the second coupler to the second analog-to-digital converter; at this time, the signal emitted by the direct digital synthesizer is amplified by the power amplifier and then transmitted to the probe, the signal reflected by the probe is sampled by the second analog-to-digital converter after being separated by the second coupler, and the detection signal (S4) output by the second analog-to-digital converter is compared with the forward signal (S3) stored during the power amplifier self-check to obtain the reflection coefficient of the probe, and then the voltage standing wave ratio and the quality factor are calculated to realize the detection of the probe matching state; the field-programmable gate array evaluates the probe state by analyzing the difference between the reflection coefficient and the preset threshold, and triggers a compensation or alarm mechanism if the parameters are abnormal to ensure the radio frequency energy transmission efficiency and signal reception sensitivity of the device.

[0044] The following uses a simple example to explain the content disclosed in the above embodiments: In a low-field nuclear magnetic resonance device, when performing a spatial localization experiment based on one-dimensional frequency encoding (i.e., an experimental method that realizes spatial localization through frequency differences), a large gradient magnetic field will cause an increase in the signal bandwidth (for example, the bandwidth of a 100 mm sample reaches 600 kHz under a high gradient), while the gain flatness of the receiving system (preamplifier and analog-to-digital converter) is usually 0.2 - 0.5 dB, which causes an amplitude error of about 2% - 5.5% for signals at different positions due to frequency differences. After introducing the real-time self-check system in this embodiment, it is possible to detect the gain of the receiving system during each test, correct the signal differences between layers, improve the accuracy of the detection results, realize the real-time monitoring and signal correction of the low-field nuclear magnetic resonance device, and improve the performance and reliability of the device. Please refer to Figure 6 The schematic diagram showing the relationship between the T2 peak area and the selected layer position before and after the receiver gain correction is shown. The abscissa is the selected layer position (unit: millimeter), and the ordinate is the T2 peak area. Figure 6 The curve (circular marked curve) of the receiver before gain correction in shows the change of the T2 peak area with the selected layer position when the gain correction is not performed. From the trend of the curve, it can be seen that there are certain fluctuations and changes in the T2 peak areas corresponding to different selected layer positions, which reflects the signal error caused by the gain difference of the receiving system. Figure 6The corrected curve of the receiver gain (the curve with square markers) in shows the variation of the T2 peak area with the slice selection position after the gain is corrected by applying the real-time self-check system of this embodiment. It can be seen that the fluctuation of the corrected curve is significantly reduced, and the difference in the T2 peak area at different slice selection positions is significantly decreased, indicating that the gain correction effectively reduces the signal error at different positions and improves the accuracy and consistency of the detection results of the low-field nuclear magnetic resonance equipment.

[0045] In summary, based on the original low-field nuclear magnetic resonance analyzer (i.e., the nuclear magnetic resonance analysis structure), this embodiment only needs to add a first coupler, a second coupler and three RF switches. Without reconstructing the original system architecture, the full-link self-check capability can be built on the basis of the original equipment to realize the self-check of the spectrometer unit, the RF power amplifier, the preamplifier and the probe. The structure is simple and the hardware cost is reduced. Moreover, in terms of equipment status monitoring and fault location, this embodiment realizes the real-time self-check of different components of the low-field nuclear magnetic resonance equipment through the precise control of each RF switch by the field programmable gate array. Once a component fails, the fault source can be quickly located, reducing the equipment downtime and maintenance cost and improving the reliability and availability of the equipment.

[0046] Although the embodiments of the present invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the present invention, and such modifications and variations all fall within the defined scope.

Claims

1. A real-time self-checking system applied to a low-field nuclear magnetic resonance device, characterized in that, The system includes: a nuclear magnetic resonance analysis structure, a first coupler, a second coupler, and three radio frequency switches; the nuclear magnetic resonance analysis structure includes a spectrometer unit, a radio frequency power amplifier, a preamplifier, and a probe; the spectrometer unit includes a field programmable gate array, a direct digital synthesizer, a first analog-to-digital converter, and a second analog-to-digital converter; The control terminals of the field programmable gate array are respectively connected to the gating terminal of the radio frequency power amplifier and the control terminals of each radio frequency switch; The output terminal of the direct digital synthesizer is connected to the input terminal of the first coupler. The output terminal of the first coupler is sequentially connected to the signal interaction terminal of the probe through the radio frequency power amplifier and the second coupler. The coupling terminal of the first coupler is connected to the common terminal of the first radio frequency switch. The output terminal of the direct digital synthesizer serves as the starting end of the self-check signal; The first radio frequency terminal of the first radio frequency switch is connected to the input terminal of the first analog-to-digital converter. The second radio frequency terminal of the first radio frequency switch is connected to the second radio frequency terminal of the second radio frequency switch. The first radio frequency terminal of the second radio frequency switch is connected to the output terminal of the radio frequency power amplifier. The common terminal of the second radio frequency switch is connected to the input terminal of the first analog-to-digital converter through the preamplifier; Both the forward terminal and the reverse terminal of the second coupler are connected to the input terminal of the second analog-to-digital converter through the third radio frequency switch.

2. The system according to claim 1, wherein The first coupler is configured to couple out a split signal from the output signal of the direct digital synthesizer for self-check of the spectrometer unit and self-check of the preamplifier; The second coupler is configured to separate the forward signal output by the radio frequency power amplifier from the reverse reflection signal of the probe for self-check of the radio frequency power amplifier and self-check of the probe.

3. The system according to claim 1, characterized in that, The first radio frequency switch, the second radio frequency switch, and the third radio frequency switch are all single-pole double-throw radio frequency switches; The single-pole double-throw radio frequency switch is configured to switch the connection path between the common terminal and the radio frequency terminal of the single-pole double-throw radio frequency switch based on the control signal sent by the control terminal of the field programmable gate array to switch the signal flow direction.

4. The system according to claim 1, wherein The nuclear magnetic resonance analysis structure further includes a transmit / receive switch; The output terminal of the radio frequency power amplifier is connected to the transmit end of the transmit / receive switch; the receive end of the transmit / receive switch is connected to the first radio frequency terminal of the second radio frequency switch; the common terminal of the transmit / receive switch is connected to the signal interaction terminal of the probe through the second coupler.

5. The system according to claim 1, wherein The forward terminal of the second coupler is connected to the first radio frequency terminal of the third radio frequency switch, and the reverse terminal of the second coupler is connected to the second radio frequency terminal of the third radio frequency switch; the common terminal of the third radio frequency switch is connected to the input terminal of the second analog-to-digital converter.

6. The system according to claim 1, wherein When the spectrometer unit performs self-check, the field programmable gate array is used to control the gate terminal of the RF power amplifier to be at a low level through the first control terminal, control the first RF switch to switch to the first RF terminal through the second control terminal, and control the second RF switch to switch to the second RF terminal through the third control terminal; the output terminal of the first analog-to-digital converter is used to output the detection signal of the self-check of the spectrometer unit.

7. The system according to claim 1, characterized in that When the preamplifier performs self-check, the field programmable gate array is used to control the gate terminal of the RF power amplifier to be at a low level through the first control terminal, control the first RF switch to switch to the second RF terminal through the second control terminal, and control the second RF switch to switch to the second RF terminal through the third control terminal; the output terminal of the first analog-to-digital converter is used to output the detection signal of the self-check of the preamplifier.

8. The system according to claim 6 or 7, wherein When the spectrometer unit performs self-check and the preamplifier performs self-check, the field programmable gate array is further used to control the third RF switch to switch to the first RF terminal or the second RF terminal through the fourth control terminal.

9. The system according to any one of claims 1 to 5, characterized in that When the RF power amplifier performs self-check, the field programmable gate array is used to control the gate terminal of the RF power amplifier to be at a high level through the first control terminal, control the first RF switch to switch to the second RF terminal through the second control terminal, control the second RF switch to switch to the first RF terminal through the third control terminal, and control the third RF switch to switch to the first RF terminal through the fourth control terminal; The output terminal of the second analog-to-digital converter is used to output the detection signal of the self-check of the RF power amplifier.

10. The system according to any one of claims 1 to 5, characterized in that When the probe performs self-check, the field programmable gate array is used to control the gate terminal of the RF power amplifier to be at a high level through the first control terminal, control the first RF switch to switch to the second RF terminal through the second control terminal, control the second RF switch to switch to the first RF terminal through the third control terminal, and control the third RF switch to switch to the second RF terminal through the fourth control terminal; The output terminal of the second analog-to-digital converter is used to output the detection signal of the self-check of the probe.

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