A constant current reference source based on nuclear magnetic resonance and its construction method

Abstract

The present invention provides a constant current reference source based on nuclear magnetic resonance and a construction method thereof, comprising a magnetic resonance unit, a signal measurement unit, a frequency measurement unit and a current control module; the current control module uses the radio frequency transmission frequency, the magnetic resonance signal frequency and the difference between the two as inputs, and adjusts the output current of the current driving module based on a neural network algorithm. The present invention converts current information into frequency information through the magnetic resonance unit, the signal measurement unit and the frequency measurement unit, and uses the high stability of magnetic resonance to control the current driving module, thereby avoiding the influence of temperature factors in the method of converting a constant voltage source into a constant current source; the frequency measurement based on the phase comparison method has a high measurement accuracy, which improves the reliability of the measurement; at the same time, the neural network algorithm is introduced to enhance the self-regulation capability of the constant current reference source, and enhance the ability of the constant current reference source to resist external interference.

Description

Technical Field

[0001] The invention relates to the technical field of constant current reference source construction, and in particular to a constant current reference source based on nuclear magnetic resonance and a construction method thereof. Background Art

[0002] Constant current reference sources are of great value in both scientific research and engineering fields. Their importance stems from the growing demand and application of stable current in electronic power. For example, they provide a high-stability reference voltage to the measurement circuit, which is used to measure the basic characteristic parameters of electronic components, generate a high-stability magnetic field for semiconductor manufacturing, sensor calibration, scientific research, medical instruments and other high-precision applications. Modern constant current reference sources mostly use bandgap reference voltage sources and high-precision current mirror circuits. This design of converting voltage sources into current sources is easily affected by temperature, and the voltage drift of the conversion circuit will also introduce errors, affecting the stability of the constant current source. The constant current reference source designed in this paper is based on the principle of magnetic resonance. It converts the current information generated by the current drive module into the frequency information of the receiving coil. The current drive module is controlled and adjusted using the high stability of magnetic resonance, and a constant current reference source with PPB-level stability can be obtained. Summary of the invention

[0003] The object of the present invention is to provide a constant current reference source based on nuclear magnetic resonance and a construction method thereof, so as to solve the above-mentioned deficiencies of the prior art.

[0004] To achieve the above object, the present invention adopts the following technical solution:

[0005] A constant current reference source based on nuclear magnetic resonance comprises a magnetic resonance unit, a signal measuring unit, a frequency measuring unit and a current control module; the magnetic resonance unit comprises a current driving module, a sensor coil connected to the current driving module via a load and capable of generating a uniform induced magnetic field, and a nuclear magnetic resonance sample placed in the center of the uniform induced magnetic field; the signal measuring unit comprises a radio frequency signal generator, a power amplifier, a radio frequency transmitting coil acting on the nuclear magnetic resonance sample to generate a magnetic resonance signal, and a radio frequency receiving coil for collecting the magnetic resonance signal, which are sequentially connected in signal.

[0006] The frequency measurement unit includes a signal conditioning circuit and a frequency measurement unit which are sequentially connected to the RF receiving coil signal, and the frequency measurement unit is also connected to a clock reference source; the current control module takes the RF transmission frequency, the magnetic resonance signal frequency and the difference between the two as inputs, and adjusts the voltage of the current driving module based on a neural network algorithm.

[0007] Furthermore, the sensor coil adopts a Helmholtz coil, a solenoid coil or other coil structures capable of generating a uniform induced magnetic field, and the nuclear magnetic resonance sample is placed in the exact center of the uniform induced magnetic field.

[0008] Furthermore, the radio frequency transmitting coil and the radio frequency receiving coil are arranged around the nuclear magnetic resonance sample, and the axial direction of the radio frequency transmitting coil is perpendicular to the axial direction of the radio frequency receiving coil, and is perpendicular to the axial direction of the sensor coil.

[0009] Furthermore, the current control module includes an input vector, a neural network, a PID vector and a PID calculation unit to synthesize a current intensity control signal, and a voltage-controlled voltage source. The input vector includes a target transmission frequency of a radio frequency signal generator, a magnetic resonance signal frequency, and a difference between the two. The neural network is a classic BP or CNN. The PID vector is composed of a proportional parameter, an integral parameter, and a differential parameter, respectively, and the calculation unit is composed of P, I, and D operators to synthesize a current intensity control signal.

[0010] A method for constructing a constant current reference source based on nuclear magnetic resonance, the method is implemented based on any of the above-mentioned constant current reference sources, and specifically comprises the following steps:

[0011] S1, setting the target output current of the current driving module, and generating a uniform induced magnetic field through the sensor coil to act on the nuclear magnetic resonance sample;

[0012] S2. setting the target transmission frequency of the radio frequency signal generator according to the uniform induced magnetic field, amplifying the radio frequency signal through the radio frequency transmitting coil and acting on the nuclear magnetic resonance sample to generate an excitation magnetic field, and searching for the magnetic resonance signal of the nuclear magnetic resonance sample;

[0013] S3, collecting the magnetic resonance signal of the nuclear magnetic resonance sample through the radio frequency receiving coil, inputting it into the frequency measurement unit after being processed by the signal conditioning circuit, and collecting the radio frequency receiving coil signal;

[0014] S4, setting the frequency sweep interval of the radio frequency signal generator and increasing it step by step, repeating S1 to S3 until a valid nuclear magnetic resonance signal is searched and the magnetic resonance frequency of the nuclear magnetic resonance sample is calculated;

[0015] S5, calculating the frequency difference based on the magnetic resonance frequency of the nuclear magnetic resonance sample obtained in step S4;

[0016] This step can be expressed by the following formulas (1) and (2):

[0017] W1=W A +nΔW (1)

[0018] ΔW1=W 01 -W 00 (2)

[0019] In formula (1) and (2): W Arepresents the frequency of the exciting magnetic field; ΔW represents the frequency sweep interval; n represents the number of levels of the frequency sweep interval increase; W1 represents the frequency of the exciting magnetic field based on the frequency sweep interval ΔW; W 00 Indicates the target transmission frequency of the RF signal generator; W 01 represents the magnetic resonance frequency of the NMR sample calculated in step S4; ΔW1 represents the frequency difference;

[0020] S6. Adjust the target transmission frequency of the RF signal generator based on the frequency difference, and repeat the above steps until the frequency difference is zero;

[0021] This step can be expressed by the following formulas (3) and (4):

[0022] W i =W i-1 -ΔW i-1 (3)

[0023] ΔW i =W 0i -W 0i-1 (4)

[0024] In formula (3) and (4): i ≥ 2; W i represents the output frequency of the RF signal generator after the i-th adjustment; ΔW i represents the frequency difference calculated after adjusting the output frequency of the RF signal generator for the i-th time; W 0i represents the magnetic resonance frequency of the nuclear magnetic resonance sample calculated after adjusting the output frequency of the radio frequency signal generator for the i-th time;

[0025] S7, based on the magnetic resonance frequency of the nuclear magnetic resonance sample when the frequency difference is zero, the locked magnetic resonance signal frequency of the nuclear magnetic resonance sample is calculated by a phase contrast method and under the premise that a clock reference source is used as a high-precision reference;

[0026] S8, using the target transmission frequency of the RF signal generator, the locked magnetic resonance signal frequency and the difference between the two as inputs of the current control module, calculating the PID control value through the neural network, and calculating the control voltage signal, outputting the driving voltage through the voltage-controlled voltage module, and adjusting the output current of the current driving module;

[0027] S9, repeat the above steps S4 to S8 until the output current of the output current driving module is stable.

[0028] Furthermore, the setting of the target transmission frequency of the radio frequency signal generator according to the uniform induced magnetic field is specifically achieved by the following method:

[0029] S21, calculating the magnitude of the magnetic field generated by the sensor coil according to the target output current value of the current driving module;

[0030] S22, calculating the target transmission frequency of the RF signal generator according to the magnitude of the magnetic field generated by the sensor coil. This step can be expressed by the following formula (5):

[0031] ω0=γB0 (5)

[0032] In formula (5), ω0 is the target transmission frequency of the RF signal generator; B0 is the magnetic field generated by the sensor coil; γ is the magnetic gyrometry constant of the particle.

[0033] It can be seen from the above technical solutions that the present invention converts current information into frequency information through a magnetic resonance unit, a signal measurement unit and a frequency measurement unit, and uses the high stability of magnetic resonance to control the current driving module, thereby avoiding the influence of temperature factors in the traditional method of converting a constant voltage source into a constant current source; the frequency measurement based on the phase comparison method has high measurement accuracy and improves the reliability of the measurement; at the same time, the neural network algorithm is introduced to enhance the autonomous adjustment capability of the constant current reference source and improve the ability of the constant current reference source to resist external interference. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a structural schematic diagram of the constant current reference source of the present invention;

[0035] Figure 2 A schematic flow chart of the steps for constructing a constant current reference source of the present invention;

[0036] Figure 3 It is a schematic diagram of the method for measuring magnetic resonance frequency of the present invention;

[0037] In the figure: 1. Current driving module; 2. Sensor coil; 3. Nuclear magnetic resonance sample; 4. RF signal generator; 5. Power amplifier; 6. RF transmitting coil; 7. RF receiving coil; 8. Signal conditioning circuit; 9. Frequency measurement unit; 10. Clock reference source; 11. Current control module; 12. Voltage-controlled voltage source. DETAILED DESCRIPTION

[0038] A preferred embodiment of the present invention is described in detail below with reference to the accompanying drawings.

[0039] like Figure 1The constant current reference source based on nuclear magnetic resonance shown in the figure includes a magnetic resonance unit, a signal measurement unit, a frequency measurement unit and a current control module 11; the magnetic resonance unit includes a current driving module 1, a sensor coil 2 connected to the current driving module 1 through a load and capable of generating a uniform induced magnetic field, and a nuclear magnetic resonance sample 3 placed in the center of the uniform induced magnetic field; the signal measurement unit includes a radio frequency signal generator 4, a power amplifier 5, a radio frequency transmitting coil 6 acting on the nuclear magnetic resonance sample 3 to generate a magnetic resonance signal, and a radio frequency receiving coil 7 for collecting magnetic resonance signals, which are sequentially connected in signal. The frequency measurement unit includes a signal conditioning circuit 8 and a frequency measurement unit 9 which are sequentially connected in signal to the radio frequency receiving coil 7, and the frequency measurement unit 9 is also connected to a clock reference source 10; the current control module 11 uses the difference between the radio frequency transmission frequency and the magnetic resonance signal frequency as input, and adjusts the voltage of the current driving module 1 based on a neural network algorithm.

[0040] In specific use, the sensor coil 2 adopts a Helmholtz coil, a solenoid coil or other coil structure capable of generating a uniform induced magnetic field, and the nuclear magnetic resonance sample 3 is placed in the center of the uniform induced magnetic field. The radio frequency transmitting coil 6 and the radio frequency receiving coil 7 are arranged around the nuclear magnetic resonance sample 3, and the axial direction of the radio frequency transmitting coil 6 and the axial direction of the radio frequency receiving coil 7 are perpendicular to each other and are both perpendicular to the axial direction of the current conversion coil 2; specifically, the radio frequency transmitting coil 6 adopts a solenoid coil, which is placed in front of the nuclear magnetic resonance sample 3, and can generate a radio frequency excitation magnetic field, and excite the nuclear spin resonance in the nuclear magnetic resonance sample 3, so as to achieve phase synchronization of the nuclear spin precession.

[0041] The current control module 11 described in this preferred embodiment includes an input vector, a neural network, a PID vector and a PID calculation unit to synthesize a current intensity control signal, and a voltage-controlled voltage source 12. The input vector includes the target transmission frequency of the RF signal generator, the magnetic resonance signal frequency and the difference between the two; the neural network is a classic BP, CNN or other model algorithm; the PID vector is composed of a proportional parameter, an integral parameter and a differential parameter, respectively, and the calculation unit or other weighted synthesized current intensity control signal is composed of P, I, D operators.

[0042] A method for constructing a constant current reference source based on nuclear magnetic resonance, the method is implemented based on the above-mentioned constant current reference source, and specifically comprises the following steps:

[0043] S1. Set the target output current of the current driving module, and generate a uniform induced magnetic field through the sensor coil to act on the nuclear magnetic resonance sample.

[0044] Specifically, the current generated by the current driving module generates a uniform induced magnetic field through the sensor coil, which can magnetize the nuclear magnetic resonance sample.

[0045] S2. The target transmission frequency of the radio frequency signal generator is set according to the uniform induced magnetic field. The radio frequency signal transmitted by the radio frequency transmitting coil after being amplified by the power amplifier acts on the nuclear magnetic resonance sample to generate an excitation magnetic field, and the magnetic resonance signal of the nuclear magnetic resonance sample is searched.

[0046] Specifically, the setting of the target transmission frequency of the radio frequency signal generator according to the uniform induced magnetic field is specifically achieved by the following method:

[0047] S21, calculating the magnitude of the magnetic field generated by the sensor coil according to the target output current value of the current driving module, and specifically calculating according to the target output current value combined with the property parameters of the sensor coil;

[0048] S22, calculating the target transmission frequency of the RF signal generator according to the magnitude of the magnetic field generated by the sensor coil. This step can be expressed by the following formula (5):

[0049] ω0=γB0 (5)

[0050] In formula (5), ω0 is the target transmission frequency of the RF signal generator; B0 is the magnetic field generated by the sensor coil; γ is the magnetic gyrometry constant of the particle.

[0051] S3, collecting the magnetic resonance signal of the nuclear magnetic resonance sample through the radio frequency receiving coil, and inputting it into the frequency measurement unit after being processed by the signal conditioning circuit to collect the radio frequency receiving coil signal.

[0052] S4, setting the frequency sweep interval of the radio frequency signal generator and increasing it step by step, repeating S1 to S3 until a valid nuclear magnetic resonance signal is searched and the magnetic resonance frequency of the nuclear magnetic resonance sample is calculated.

[0053] S5, calculating the frequency difference based on the magnetic resonance frequency of the nuclear magnetic resonance sample obtained in step S4;

[0054] This step can be expressed by the following formulas (1) and (2):

[0055] W1=W A +nΔW (1)

[0056] ΔW1=W 01 -W 00 (2)

[0057] In formula (1) and (2): W A represents the frequency of the exciting magnetic field; ΔW represents the frequency sweep interval; n represents the number of levels of the frequency sweep interval increase; W1 represents the frequency of the exciting magnetic field based on the frequency sweep interval ΔW; W 00 Indicates the target transmission frequency of the RF signal generator; W 01represents the magnetic resonance frequency of the NMR sample calculated in step S4; ΔW1 represents the frequency difference;

[0058] S6. Adjust the target transmission frequency of the RF signal generator based on the frequency difference, and repeat the above steps until the frequency difference is zero;

[0059] This step can be expressed by the following formulas (3) and (4):

[0060] W i =W i-1 -ΔW i-1 (3)

[0061] ΔW i =W 0i -W 0i-1 (4)

[0062] In formula (3) and (4): i ≥ 2; W i represents the output frequency of the RF signal generator after the i-th adjustment; ΔW i represents the frequency difference calculated after adjusting the output frequency of the RF signal generator for the i-th time; W 0i It represents the magnetic resonance frequency of the nuclear magnetic resonance sample calculated after adjusting the output frequency of the radio frequency signal generator for the i-th time.

[0063] S7. Based on the magnetic resonance frequency of the nuclear magnetic resonance sample when the frequency difference is zero, the locked magnetic resonance signal frequency of the nuclear magnetic resonance sample is calculated by a phase contrast method and under the premise that a clock reference source is used as a high-precision reference.

[0064] The locked magnetic resonance signal frequency described in this preferred embodiment is obtained by the following method: when the RF receiving coil collects the magnetic resonance signal and transmits it to the frequency measurement unit through the signal conditioning circuit, the clock reference signal is transmitted to the frequency measurement unit; as shown in the attached figure Figure 3 As shown, when the two signals are both rising edges, counting starts, and when they are both falling edges, counting stops. Specifically, the number of magnetic resonance signal pulse counts is N X , the number of clock reference signal pulse counts is N r , the clock reference frequency is known to be f r , assuming the frequency of the magnetic resonance signal is f X , use contrast measurement to select two phase coincidences at the rising or falling edge, start counting, and calculate the frequency f of the nuclear magnetic resonance signal X This phase comparison method is only used as an example, and other phase comparison methods are obviously within the scope of the rights protection.

[0065] S8. The target transmission frequency of the RF signal generator, the locked magnetic resonance signal frequency and the difference between the two are used as inputs of the current control module, the PID control value and the control voltage signal are calculated through the neural network, the driving voltage is output through the voltage-controlled voltage module, and the output current of the current driving module is adjusted.

[0066] S9, repeat the above steps S4 to S8 until the output current of the output current driving module is stable.

[0067] The entire constant current reference source control loop described in this preferred embodiment includes two loop processes, one is a control loop, and the other is a measurement loop. The control loop first sets the theoretical output value, then uses the measurement loop to measure, obtains the deviation value, and then obtains the new output value by the neural network, and then repeats the process to obtain the final stable value. In specific operations, the allowable error range of the output current can be set as needed, and when the output current value reaches the allowable error range, the output current can be considered stable.

[0068] The above-described embodiments are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A constant current reference source based on nuclear magnetic resonance, characterized in that: It includes a magnetic resonance unit, a signal measurement unit, a frequency measurement unit and a current control module; The magnetic resonance unit comprises a current driving module, a sensor coil connected to the current driving module via a load and capable of generating a uniform induced magnetic field, and a nuclear magnetic resonance sample placed in the exact center of the uniform induced magnetic field; The signal measuring unit comprises a radio frequency signal generator, a power amplifier, a radio frequency transmitting coil for acting on a nuclear magnetic resonance sample to generate a magnetic resonance signal, and a radio frequency receiving coil for collecting the magnetic resonance signal, which are sequentially connected in signal. The frequency measurement unit comprises a signal conditioning circuit and a frequency measurement unit which are sequentially connected to the radio frequency receiving coil signal, and the frequency measurement unit is also connected to a clock reference source; The current control module takes the radio frequency transmission frequency, the magnetic resonance signal frequency and the difference between the two as inputs, and adjusts the output current of the current driving module based on a neural network algorithm.

2. A constant current reference source based on nuclear magnetic resonance according to claim 1, characterized in that: The sensor coil adopts a Helmholtz coil, a solenoid coil or other coil structures capable of generating a uniform induced magnetic field, and the nuclear magnetic resonance sample is placed in the exact center of the uniform induced magnetic field.

3. A constant current reference source based on nuclear magnetic resonance according to claim 2, characterized in that: The radio frequency transmitting coil and the radio frequency receiving coil are arranged around the nuclear magnetic resonance sample, and the axial direction of the radio frequency transmitting coil is perpendicular to the axial direction of the radio frequency receiving coil, and is also perpendicular to the axial direction of the sensor coil.

4. A constant current reference source based on nuclear magnetic resonance according to claim 1, characterized in that: The current control module includes an input vector, a neural network, a PID vector and a PID calculation unit to synthesize a current intensity control signal, and a voltage-controlled voltage source. The input vector includes a target transmission frequency of a radio frequency signal generator, a magnetic resonance signal frequency, and a difference between the two. The neural network is a classic BP or CNN. The PID vector is composed of a proportional parameter, an integral parameter, and a differential parameter, respectively, and the calculation unit is composed of P, I, and D operators to synthesize a current intensity control signal.

5. A method for constructing a constant current reference source based on nuclear magnetic resonance, the method being implemented based on the constant current reference source described in any one of claims 1 to 4, characterized in that: The specific steps include: S1, setting the target output current of the current driving module, and generating a uniform induced magnetic field through the sensor coil to act on the nuclear magnetic resonance sample; S2. Setting the target transmission frequency of the radio frequency signal generator according to the uniform induced magnetic field, amplifying the radio frequency signal through the radio frequency transmitting coil and acting on the nuclear magnetic resonance sample to generate an excitation magnetic field, and searching for the magnetic resonance signal of the nuclear magnetic resonance sample; S3, collecting the magnetic resonance signal of the nuclear magnetic resonance sample through the radio frequency receiving coil, inputting it into the frequency measurement unit after being processed by the signal conditioning circuit, and collecting the radio frequency receiving coil signal; S4, setting the frequency sweep interval of the radio frequency signal generator and increasing it step by step, repeating S1 to S3 until a valid nuclear magnetic resonance signal is searched and the magnetic resonance frequency of the nuclear magnetic resonance sample is calculated; S5, calculating the frequency difference based on the magnetic resonance frequency of the nuclear magnetic resonance sample obtained in step S4; This step can be expressed by the following formulas (1) and (2): W1=W A +nΔW (1) ΔW1=W 01 -IN 00 (2) In formula (1) and (2): W A represents the frequency of the exciting magnetic field; ΔW represents the frequency sweep interval; n represents the number of levels of the frequency sweep interval increase; W1 represents the frequency of the exciting magnetic field based on the frequency sweep interval ΔW; W 00 Indicates the target transmission frequency of the RF signal generator; W 01 represents the magnetic resonance frequency of the NMR sample calculated in step S4; ΔW1 represents the frequency difference; S6. Adjust the target transmission frequency of the radio frequency signal generator based on the frequency difference, and repeat the above steps until the frequency difference is zero; This step can be expressed by the following formulas (3) and (4): IN i =In i-1 -ΔW i-1 (3) ΔW i =In 0i -IN 0i-1 (4) In formula (3) and (4): i ≥ 2; W i represents the output frequency of the RF signal generator after the i-th adjustment; ΔW i represents the frequency difference calculated after adjusting the output frequency of the RF signal generator for the i-th time; W 0i represents the magnetic resonance frequency of the nuclear magnetic resonance sample calculated after adjusting the output frequency of the radio frequency signal generator for the i-th time; S7, based on the magnetic resonance frequency of the nuclear magnetic resonance sample when the frequency difference is zero, the locked magnetic resonance signal frequency of the nuclear magnetic resonance sample is calculated by a phase contrast method and under the premise that a clock reference source is used as a high-precision reference; S8, using the target transmission frequency of the RF signal generator, the locked magnetic resonance signal frequency and the difference between the two as inputs of the current control module, calculating the PID control value through the neural network, and calculating the control voltage signal, outputting the driving voltage through the voltage-controlled voltage module, and adjusting the output current of the current driving module; S9, repeat the above steps S4 to S8 until the output current of the current driving module is stable.

6. The method for constructing a constant current reference source based on nuclear magnetic resonance according to claim 5, characterized in that: The setting of the target transmission frequency of the radio frequency signal generator according to the uniform induced magnetic field is specifically achieved by the following method: S21, calculating the magnitude of the magnetic field generated by the sensor coil according to the target output current value of the current driving module; S22, calculating the target transmission frequency of the RF signal generator according to the magnitude of the magnetic field generated by the sensor coil. This step can be expressed by the following formula (5): ω0=γB0 (5) In formula (5), ω0 is the target transmission frequency of the RF signal generator; B0 is the magnetic field generated by the sensor coil; γ is the magnetic gyrometry constant of the particle.

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