A real-time self-test system for low-field nuclear magnetic resonance equipment

Abstract

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

Description

Technical Field

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

[0002] As a multidisciplinary cross-analysis tool, low-field nuclear magnetic resonance (LF-NMR) technology has demonstrated significant application value in biomedical testing, industrial materials characterization, and geological core pore structure analysis. Its non-destructive quantitative analysis capabilities provide key data support for quality control and scientific research.

[0003] However, when low-field NMR equipment is in operation for extended periods, the operating conditions of core components such as the RF power amplifier, preamplifier, RF coil, and magnet are susceptible to changes, which can reduce the reliability of test data and affect the accuracy of analysis results. Therefore, real-time self-testing of low-field NMR equipment is crucial. Currently, most NMR equipment lacks a real-time self-test system and only performs tests at startup or at a fixed interval, failing to provide component status data for each sampling period. While some equipment does have self-test systems, these systems are complex, costly, and unable to accurately locate the source of faults, hindering widespread adoption.

[0004] Therefore, there is an urgent need to develop a real-time self-test 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-test system for low-field nuclear magnetic resonance equipment to solve the problems that existing low-field nuclear magnetic resonance equipment lacks real-time monitoring capabilities, and some self-test systems have complex structures, high costs, and cannot accurately locate the source of faults.

[0006] The present invention provides a real-time self-test system for low-field nuclear magnetic resonance equipment, the system comprising: a nuclear magnetic resonance analysis structure, a first coupler, a second coupler, and three radio frequency switches; the nuclear magnetic resonance analysis structure comprises a spectrometer unit, a radio frequency power amplifier, a preamplifier, and a probe; the spectrometer unit comprises a field programmable gate array, a direct digital synthesizer, a first analog-to-digital converter, and a second analog-to-digital converter;

[0007] The control end of the field programmable gate array is connected to the gate end of the radio frequency power amplifier and the control end of each radio frequency switch respectively;

[0008] 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 connected to the signal interaction end of the probe through the RF power amplifier and the second coupler in sequence, and the coupling end of the first coupler is connected to the common end of the first RF switch; the output end of the direct digital synthesizer serves as the starting end of the self-test signal;

[0009] 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, and the common terminal of the second RF switch is connected to the input terminal of the first analog-to-digital converter through the preamplifier;

[0010] The forward end and the reverse end of the second coupler are both connected to the input end of the second analog-to-digital converter through a third radio frequency switch.

[0011] In an optional embodiment, the first coupler is used to couple a branch signal from the output signal of the direct digital synthesizer to perform a self-test of the spectrometer unit and a self-test of the preamplifier;

[0012] The second coupler is used to separate the forward signal output by the RF power amplifier and the reverse reflected signal of the probe, so as to perform self-test of the RF power amplifier and the probe.

[0013] In an optional embodiment, the first RF switch, the second RF switch and the third RF switch are all single-pole double-throw RF switches;

[0014] The single-pole double-throw radio frequency switch is used to switch the connection path between the common end and the radio frequency end of the single-pole double-throw radio frequency switch based on the control signal sent by the control end of the field programmable gate array, so as to switch the signal flow direction.

[0015] In an optional embodiment, the nuclear magnetic resonance analysis structure further includes a transmit / receive switch;

[0016] The output end of the RF power amplifier is connected to the transmitting end of the transmit / receive switch; the receiving end of the transmit / receive switch is connected to the first RF end of the second RF switch; and the common end of the transmit / receive switch is connected to the signal interaction end of the probe through the second coupler.

[0017] In an optional embodiment, the forward end of the second coupler is connected to the first RF end of the third RF switch, the reverse end of the second coupler is connected to the second RF end of the third RF switch; and the common end of the third RF switch is connected to the input end of the second analog-to-digital converter.

[0018] In an optional embodiment, when the spectrometer unit self-tests, the field programmable gate array is used to control the gate end of the RF power amplifier to a low level through the first control end, control the first RF switch to switch to the first RF end through the second control end, and control the second RF switch to switch to the second RF end through the third control end; the output end of the first analog-to-digital converter is used to output the detection signal of the spectrometer unit self-test.

[0019] In an optional embodiment, during the preamplifier self-test, the field programmable gate array is used to control the gate end of the RF power amplifier to a low level through the first control end, control the first RF switch to switch to the second RF end through the second control end, and control the second RF switch to switch to the second RF end through the third control end; the output end of the first analog-to-digital converter is used to output a detection signal of the preamplifier self-test.

[0020] In an optional embodiment, during the self-test of the spectrometer unit and the self-test of the preamplifier, the field programmable gate array is further configured to control the third radio frequency switch to switch to the first radio frequency end or the second radio frequency end through the fourth control end.

[0021] In an optional embodiment, when the RF power amplifier performs self-test, the field programmable gate array is used to control the gate end of the RF power amplifier to a high level through the first control end, control the first RF switch to switch to the second RF end through the second control end, control the second RF switch to switch to the first RF end through the third control end, and control the third RF switch to switch to the first RF end through the fourth control end; the output end of the second analog-to-digital converter is used to output a detection signal of the RF power amplifier self-test.

[0022] In an optional embodiment, when the probe self-tests, the field programmable gate array is used to control the gate end of the RF power amplifier to a high level through the first control end, control the first RF switch to switch to the second RF end through the second control end, control the second RF switch to switch to the first RF end through the third control end, and control the third RF switch to switch to the second RF end through the fourth control end; the output end of the second analog-to-digital converter is used to output the detection signal of the probe self-test.

[0023] The technical solution provided by the present invention can have the following beneficial effects:

[0024] The present invention only requires the addition of a first coupler, a second coupler, and three radio frequency switches to the original low-field nuclear magnetic resonance analyzer (i.e., the nuclear magnetic resonance analysis structure). Without reconstructing the original system architecture, full-link self-test capabilities can be built on the original equipment, enabling self-tests for the spectrometer unit, radio frequency power amplifier, preamplifier, and probe. This simple structure reduces hardware costs. Furthermore, regarding equipment status monitoring and fault location, the present invention precisely controls each radio frequency switch through a field programmable gate array, enabling real-time self-tests of the various components of the low-field nuclear magnetic resonance equipment. Once a component fails, the source of the fault can be quickly located, reducing equipment downtime and maintenance costs, and improving equipment reliability and availability. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0026] Figure 1 2 is a schematic structural diagram of a real-time self-test system for low-field nuclear magnetic resonance equipment according to an embodiment of the present invention;

[0027] Figure 2 is a schematic diagram of a self-test sequence of a spectrometer unit according to an embodiment of the present invention;

[0028] Figure 3 is a schematic diagram of a preamplifier self-test sequence according to an embodiment of the present invention;

[0029] Figure 4 is a schematic diagram of a self-test sequence of a radio frequency power amplifier according to an embodiment of the present invention;

[0030] Figure 5 is a schematic diagram of a probe self-test sequence according to an embodiment of the present invention;

[0031] Figure 6 3 is a schematic diagram of the relationship between the T2 peak area and the layer selection position before and after receiver gain correction according to an embodiment of the present invention. DETAILED DESCRIPTION

[0032] To make the purpose, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making creative efforts shall fall within the scope of protection of the present invention.

[0033] According to an embodiment of the present invention, a real-time self-test system embodiment for low-field nuclear magnetic resonance equipment is provided. Figure 1 is a structural diagram of a real-time self-test system for low-field nuclear magnetic resonance equipment according to an embodiment of the present invention. Figure 1 As 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 Figure 1 The first RF switch in Figure 1 SPDT1 in), the second RF switch (i.e. Figure 1 SPDT2 in) and the third RF switch (i.e. Figure 1 SPDT3 in the NMR 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 1 FPGA in), direct digital synthesizer (i.e. Figure 1 DDS in), the first analog-to-digital converter (i.e. Figure 1 ADC1 in the ADC) and the second analog-to-digital converter (i.e. Figure 1 ADC2 in );

[0034] The control end of the field programmable gate array is connected to the gate end of the radio frequency power amplifier and the control end of each radio frequency switch respectively; specifically: the first control end of the field programmable gate array (i.e. Figure 1 GATE1 in the figure) is connected to the gate terminal of the RF power amplifier (i.e. Figure 1 GATE in), the second control terminal of the field programmable gate array (i.e. Figure 1 The GATE2 in the field programmable gate array is connected to the control terminal of the first RF switch, and the third control terminal of the field programmable gate array (ie Figure 1 The GATE3 in the field programmable gate array is connected to the control terminal of the second RF switch, and the fourth control terminal of the field programmable gate array (ie Figure 1 The GATE4 in the embodiment is connected to the control end of the third RF switch.

[0035] The output end of the direct digital synthesizer (the output end of the direct digital synthesizer serves as the starting end of the self-test signal) is connected to the input end (IN) of the first coupler, and the output end (OUT) of the first coupler is connected to the signal interaction end of the probe through the RF power amplifier and the second coupler in sequence; specifically: the output end (OUT) of the first coupler is connected to the input end (IN) of the RF power amplifier, the output end (OUT) of the RF power amplifier is connected to the input end (IN) of the second coupler, and the output end (OUT) of the second coupler is connected to the signal interaction end of the probe.

[0036] The coupling end (COUP) of the first coupler is connected to the common end of the first RF switch; the first RF end (port 0) of the first RF switch is connected to the input end of the first analog-to-digital converter, the second RF end (port 1) of the first RF switch is connected to the second RF end (port 1) of the second RF switch, the first RF end (port 0) of the second RF switch is connected to the output end (OUT) of the RF power amplifier, and the common end of the second RF switch is connected to the input end of the first analog-to-digital converter through the preamplifier; specifically: the common end of the second RF switch is connected to the input end of the preamplifier, and the output end of the preamplifier is connected to the input end of the first analog-to-digital converter.

[0037] The forward end (FOR) and the reverse end (REV) of the second coupler are both connected to the input end of the second analog-to-digital converter through a third radio frequency switch.

[0038] Furthermore, the field programmable gate array is the control center of the entire system, responsible for outputting control signals, controlling the switching state of the RF power amplifier and the switching of each RF switch. The direct digital synthesizer is used to generate high-precision, high-stability RF signals as excitation signals and self-test signal sources. The first analog-to-digital converter is used to collect the self-test signals of the spectrometer unit and the preamplifier, and convert 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 RF power amplifier and the probe, and analyze the forward and reverse power. The RF power amplifier is used to amplify the RF signal output by the direct digital synthesizer and drive the probe to generate a nuclear magnetic resonance signal. The preamplifier is used to amplify the nuclear magnetic resonance signal returned by the probe and input it into the first analog-to-digital converter for digital processing. The probe is the part that is in direct contact with the sample, and is used to transmit RF signals to the sample and receive the response signal generated by the sample.

[0039] In an optional embodiment, the first coupler may be a low-power coupler, and the second coupler may be a dual-channel directional coupler;

[0040] The first coupler is used to couple a branch signal from the output signal of the direct digital synthesizer to perform a self-test of the spectrometer unit and the preamplifier; that is, a small portion of power is extracted from the output signal of the direct digital synthesizer for the self-test of the spectrometer unit and the preamplifier, and the main signal continues to be transmitted to the power amplifier;

[0041] The second coupler is used to separate the forward signal output by the RF power amplifier and the reverse reflected signal of the probe to perform RF power amplifier self-test and probe self-test; that is, to separate the forward output signal of the RF power amplifier and the reverse reflected signal of the probe, which are used for RF power amplifier self-test and probe self-test respectively.

[0042] In an optional embodiment, the first RF switch, the second RF switch and the third RF switch are all single-pole double-throw RF switches;

[0043] The single-pole double-throw radio frequency switch is used to switch the connection path between the common end and the radio frequency end of the single-pole double-throw radio frequency switch based on the control signal sent by the control end of the field programmable gate array, so as to switch the signal flow direction.

[0044] Furthermore, the first RF switch can direct the coupled signal to different paths by switching the connection between the common terminal and different RF terminals, which can be used for spectrometer unit self-test or preamplifier self-test. The second RF switch can control whether the signal passes through the preamplifier by switching the connection between the common terminal and different RF terminals, thereby realizing preamplifier self-test. The third RF switch can collect forward and reverse signals separately by switching the connection between the common terminal and different RF terminals, realizing RF power amplifier self-test and probe self-test.

[0045] In an optional embodiment, the NMR analysis structure further includes a transmit / receive switch (i.e. Figure 1 T / X switch in );

[0046] The output end (OUT) of the RF power amplifier is connected to the transmitting end (T) of the transmitting / receiving switch; the receiving end (X) of the transmitting / receiving switch is connected to the first RF end (port 0) of the second RF switch; the common end (T / X) of the transmitting / receiving switch is connected to the signal interaction end of the probe through the second coupler, specifically: the common end (T / X) of the transmitting / receiving switch is connected to the input end (IN) of the second coupler, and the output end (OUT) of the second coupler is connected to the signal interaction end of the probe.

[0047] Furthermore, the transmit / receive switch is used to switch between signal transmission and signal reception modes. In signal transmission mode, the transmit / receive switch transmits the RF signal output by the RF power amplifier to the probe, allowing the probe to transmit the signal to the sample. In signal reception mode, the transmit / receive switch transmits the nuclear magnetic resonance signal received by the probe to the second RF switch, where it is amplified and subsequently processed by the preamplifier. In transmission mode, the common terminal (T / X) of the transmit / receive switch is connected to the transmitting terminal (T). The signal output by the RF power amplifier passes through the transmit / receive switch, the second coupler, and finally to the signal exchange terminal of the probe, where it is transmitted by the probe. In reception mode, the signal received by the probe is transmitted through the second coupler to the common terminal (T / X) of the transmit / receive switch. At this point, the common terminal (T / X) of the transmit / receive switch is connected to the receiving terminal (X). The signal is output from the receiving terminal (X), transmitted through the second RF switch to the preamplifier for amplification, and then converted to a digital signal by the first analog-to-digital converter for subsequent processing and analysis.

[0048] In an optional embodiment, the forward end (FOR) of the second coupler is connected to the first RF end (port 0) of the third RF switch, and the reverse end (REV) of the second coupler is connected to the second RF end (port 1) of the third RF switch; the common end of the third RF switch is connected to the input end of the second analog-to-digital converter.

[0049] In an optional embodiment, when the spectrometer unit self-tests, the field programmable gate array is used to control the gate end of the RF power amplifier to a low level through the first control end, control the first RF switch to switch to the first RF end through the second control end, and control the second RF switch to switch to the second RF end through the third control end; the output end of the first analog-to-digital converter is used to output the detection signal of the spectrometer unit self-test.

[0050] Furthermore, the principle of the spectrometer unit self-test is as follows: When the direct digital synthesizer and analog-to-digital converter within the spectrometer unit self-test, the field programmable gate array outputs a control signal to control the first RF switch to switch to the first RF terminal (port 0), the second RF switch to switch to the second RF terminal (port 1), and the third RF switch to switch to either the second RF terminal (port 1) or the first RF terminal (port 0). At this time, the RF power amplifier is gated to a low level (0V), and the RF power amplifier is turned off. The signal emitted by the direct digital synthesizer is coupled out of a portion of its power through the first coupler, passes through the first RF switch, and enters the first analog-to-digital converter, obtaining the spectrometer unit self-test detection signal (S1), thereby implementing spectrometer detection. Please refer to the following for details: Figure 2 The schematic diagram of the self-test sequence of the spectrometer unit is shown in FIG. Figure 2 In the CMOS, the direct digital synthesizer (DDS) sends out an RF signal as the excitation signal and self-test signal source; GATE1 is set low (turning off the RF power amplifier); GATE2 is set low (switching the first RF switch to port 0); GATE3 is set high (switching the second RF switch to port 1); GATE4 is arbitrary (the state of the third RF switch does not affect the spectrometer self-test).

[0051] That is to say, during the self-test process of the spectrometer unit of the low-field nuclear magnetic equipment, the field programmable gate array uses a control signal to make the system enter a specific detection state: first, the gate end of the RF power amplifier is set to a low level to turn off the power amplifier to prevent the self-test signal from entering the subsequent link; then the first RF switch is controlled to switch to the first RF end (port 0), and the second RF switch is controlled to switch to the second RF end (port 1), forming an independent detection path from the direct digital synthesizer through the first coupler coupling end, the first RF switch to the first analog-to-digital converter; at this time, the signal emitted 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 pure internal loop detection of the core components of the spectrometer unit, eliminating interference from the back-end link, and ensuring detection accuracy.

[0052] In an optional embodiment, when the preamplifier performs self-test, the field programmable gate array is used to control the gate end of the RF power amplifier to a low level through the first control end, control the first RF switch to switch to the second RF end through the second control end, and control the second RF switch to switch to the second RF end through the third control end; the output end of the first analog-to-digital converter is used to output a detection signal of the preamplifier self-test.

[0053] Furthermore, the principle of the preamplifier self-test is as follows: During the preamplifier self-test, the first RF switch is switched to the second RF end (port 1), the second RF switch is switched to the second RF end (port 1), and the third RF switch is switched to either the second RF end (port 1) or the first RF end (port 0). At this time, the RF power amplifier is gated to a low level (0V), and the RF power amplifier is turned off. The signal emitted by the direct digital synthesizer is coupled out of a portion of its power through the first coupler, then amplified by the preamplifier after passing through the first and second RF switches, and then enters the first analog-to-digital converter to obtain the preamplifier self-test detection signal (S2), thus implementing the preamplifier detection. Please refer to the following for details: Figure 3 The schematic diagram of the preamplifier self-test sequence is shown in Figure 3 In the example, the direct digital synthesizer (DDS) sends out an RF signal as the excitation signal and self-test signal source; GATE1 is set low (turning off the RF power amplifier); GATE2 is set high (switching the first RF switch to port 1); GATE3 is set high (switching the second RF switch to port 1); GATE4 is arbitrary (the state of the third RF switch does not affect the preamplifier self-test).

[0054] That is to say, during the self-test process of the preamplifier of the low-field nuclear magnetic resonance equipment, the field programmable gate array uses a control signal to make the system enter a specific detection state. First, the gate end of the RF power amplifier is set to a low level to turn off the power amplifier to prevent the self-test signal from entering the subsequent link; then the first RF switch is controlled to switch to the second RF end (port 1), and the second RF switch is controlled to switch to the second RF end (port 1), forming a detection path from the direct digital synthesizer through the first coupler coupling end, 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 coupling and switching transmission, 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, thereby realizing independent detection of the preamplifier; this self-test mechanism is reconstructed through the hardware path to quickly verify the performance of the preamplifier without affecting other components, providing reliable protection for high-precision detection of low-field nuclear magnetic resonance equipment.

[0055] In an optional embodiment, during the self-test of the spectrometer unit and the preamplifier, the field programmable gate array is further configured to control the third radio frequency switch to switch to the first radio frequency end or the second radio frequency end via the fourth control end.

[0056] In an optional embodiment, when the RF power amplifier performs self-test, the field programmable gate array is used to control the gate end of the RF power amplifier to a high level through the first control end, control the first RF switch to switch to the second RF end through the second control end, control the second RF switch to switch to the first RF end through the third control end, and control the third RF switch to switch to the first RF end through the fourth control end; the output end of the second analog-to-digital converter is used to output a detection signal of the RF power amplifier self-test.

[0057] Furthermore, the RF power amplifier self-test principle is as follows: During the RF power amplifier self-test, 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 RF power amplifier gate is high (1V), and the RF power amplifier is turned on. The signal output by the RF power amplifier passes through the second coupler, and a portion of the forward signal (S3) is separated and enters the second analog-to-digital converter to realize the RF power amplifier self-test. See here. Figure 4 The schematic diagram of the RF power amplifier self-test sequence is shown. Figure 4In the example, the direct digital synthesizer (DDS) sends out an RF signal as the excitation signal and self-test signal source; GATE1 is set high (turning on the RF power amplifier); GATE2 is set high (switching the first RF switch to port 1); GATE3 is set low (switching the second RF switch to port 0); GATE4 is arbitrary (the state of the third RF switch does not affect the RF power amplifier self-test).

[0058] 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 uses a control signal to make the system enter a specific detection state: first, the gate end of the RF 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 RF switch is controlled to switch to the second RF end (port 1), and the signal of the direct digital synthesizer is directed to the power amplifier input end; the second RF switch is controlled to switch to the first RF end (port 0), and the power amplifier output signal is connected to the second coupler; the third RF switch is controlled to switch to the first RF end (port 0), and the forward signal separated by the second coupler is directed 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, thereby realizing independent detection of the power amplifier.

[0059] In an optional embodiment, when the probe self-tests, the field programmable gate array is used to control the gate end of the RF power amplifier to a high level through the first control end, control the first RF switch to switch to the second RF end through the second control end, control the second RF switch to switch to the first RF end through the third control end, and control the third RF switch to switch to the second RF end through the fourth control end; the output end of the second analog-to-digital converter is used to output the detection signal of the probe self-test.

[0060] Furthermore, the probe self-test principle is as follows: During the probe self-test, the first RF switch switches to the second RF port (port 1), the second RF switch switches to the first RF port (port 0), and the third RF switch switches to the second RF port (port 1). At this time, the RF power amplifier is gated to a high level (1V), turning on the RF power amplifier. The signal output by the RF power amplifier passes through the second coupler, separating a portion of the reverse signal (S4) that enters the second analog-to-digital converter. The reverse signal (S4) is compared with the forward signal (S3) detected during the RF power amplifier self-test to obtain the probe's reflection coefficient, thus achieving probe detection. See here. Figure 5 The schematic diagram of the probe self-test sequence is shown in Figure 5In the figure, the direct digital synthesizer (DDS) sends out an RF signal as the excitation signal and self-test signal source; GATE1 is set high (turning on the RF power amplifier); GATE2 is set low (switching the first RF switch to port 0); GATE3 is set high (switching the second RF switch to port 1); GATE4 is set high (switching the third RF switch to port 1).

[0061] That is to say, during the self-test process of the probe of the low-field nuclear magnetic resonance equipment, the field programmable gate array uses the control signal to make the system enter a specific detection state: first, the gate terminal of the RF 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 RF switch is controlled to switch to the second RF terminal (port 1), and the signal of the direct digital synthesizer is directed to the input terminal of the power amplifier; the second RF switch is controlled to switch to the first RF terminal (port 0), and the output signal of the power amplifier is connected to the second coupler; the third RF switch is controlled to switch to the second RF terminal (port 1), and the reverse signal separated by the second coupler (from the probe) is connected to the second coupler. The signal from the direct digital synthesizer is amplified by the power amplifier and then transmitted to the probe. The signal reflected by the probe is separated by the second coupler and sampled by the second analog-to-digital converter. The reverse signal (S4) output by the second analog-to-digital converter is compared with the forward signal (S3) stored during the power amplifier self-test to obtain the reflection coefficient of the probe, and then the voltage standing wave ratio and quality factor are calculated to detect the matching status of the probe. The field programmable gate array evaluates the probe status by analyzing the difference between the reflection coefficient and the preset threshold. If the parameter is abnormal, the compensation or alarm mechanism is triggered to ensure the RF energy transmission efficiency and signal reception sensitivity of the equipment.

[0062] The following is an explanation of the contents disclosed in the above embodiment through simple examples:

[0063] In low-field NMR equipment, when conducting spatial positioning experiments based on one-dimensional frequency encoding (i.e., experimental methods that achieve spatial positioning through frequency differences), larger gradient magnetic fields lead to increased signal bandwidth (e.g., a 100mm sample has a bandwidth of 600kHz under high gradients). However, the gain flatness of the receiving system (preamplifier and analog-to-digital converter) is typically 0.2-0.5dB, resulting in amplitude errors of approximately 2%-5.5% in signals at different locations due to frequency differences. The introduction of the real-time self-test system in this embodiment enables the gain of the receiving system to be checked during each test, correcting for inter-layer signal differences. This improves the accuracy of the test results, enables real-time monitoring and signal correction of low-field NMR equipment, and enhances the performance and reliability of the equipment. (See [1] for details.) Figure 6 The figure shows the relationship between the T2 peak area and the layer selection position before and after the receiver gain correction. The horizontal axis is the layer selection position (unit: millimeter) and the vertical axis is the T2 peak area. Figure 6The receiver gain correction curve (circled curve) in Figure 3 shows how the T2 peak area varies with layer selection position without gain correction. The curve shows fluctuations and variations in the T2 peak area at different layer selection positions, reflecting signal errors caused by differences in receiving system gain. Figure 6 The receiver gain correction curve (square-marked curve) in Figure 3 shows how the T2 peak area changes with the selected layer position after gain correction using the real-time self-test system of this embodiment. As can be seen, the curve fluctuations are significantly reduced after correction, and the difference in T2 peak area at different selected layer positions is significantly reduced, indicating that gain correction effectively reduces signal errors at different positions and improves the accuracy and consistency of test results from low-field NMR equipment.

[0064] In summary, this embodiment only requires the addition of a first coupler, a second coupler, and three RF switches to the original low-field nuclear magnetic resonance analyzer (i.e., the nuclear magnetic resonance analysis structure). Without reconstructing the original system architecture, this embodiment can build a full-link self-test capability based on the original equipment, enabling self-tests for the spectrometer unit, RF power amplifier, preamplifier, and probe. This simplifies the structure and reduces hardware costs. Furthermore, regarding equipment status monitoring and fault location, this embodiment achieves real-time self-testing of the various components of the low-field nuclear magnetic resonance equipment through precise control of each RF switch using a field programmable gate array. Once a component fails, the source of the fault can be quickly located, reducing equipment downtime and repair costs, and improving equipment reliability and availability.

[0065] Although the embodiments of the present invention have been described with reference to the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the present invention, and such modifications and variations are all within the defined scope.

Claims

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

2. The system according to claim 1, wherein: The first coupler is used to couple a branch signal from the output signal of the direct digital synthesizer to perform a self-test of the spectrometer unit and a self-test of the preamplifier; The second coupler is used to separate the forward signal output by the RF power amplifier and the reverse reflected signal of the probe, so as to perform self-test of the RF power amplifier and the probe.

3. The system according to claim 1, wherein: 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 radio frequency switch is used to switch the connection path between the common end and the radio frequency end of the single-pole double-throw radio frequency switch based on the control signal sent by the control end of the field programmable gate array, so as to switch the signal flow direction.

4. The system according to claim 1, wherein: The nuclear magnetic resonance analysis structure also includes a transmit / receive switch; The output end of the RF power amplifier is connected to the transmitting end of the transmit / receive switch; the receiving end of the transmit / receive switch is connected to the first RF end of the second RF switch; and the common end of the transmit / receive switch is connected to the signal interaction end of the probe through the second coupler.

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

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

7. The system according to claim 1, wherein: During the preamplifier self-test, the field programmable gate array is used to control the gate end of the RF power amplifier to a low level through the first control end, control the first RF switch to switch to the second RF end through the second control end, and control the second RF switch to switch to the second RF end through the third control end; the output end of the first analog-to-digital converter is used to output a detection signal of the preamplifier self-test.

8. The system according to claim 6 or 7, characterized in that During the self-test of the spectrometer unit and the preamplifier, the field programmable gate array is further configured to control the third radio frequency switch to switch to the first radio frequency end or the second radio frequency end through the fourth control end.

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

10. The system according to any one of claims 1 to 5, characterized in that During the self-test of the probe, the field programmable gate array is used to control the gate end of the radio frequency power amplifier to be high through the first control end, control the first radio frequency switch to switch to the second radio frequency end through the second control end, control the second radio frequency switch to switch to the first radio frequency end through the third control end, and control the third radio frequency switch to switch to the second radio frequency end through the fourth control end; The output end of the second analog-to-digital converter is used to output a detection signal of the probe self-test.

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