Low-power, high-precision magnetic resonance signal phase closed-loop control method and system

Abstract

The application provides a low-power-consumption and high-precision magnetic resonance signal phase closed-loop control method and system, which comprises the following steps: first, a magnetic field excitation signal is generated by a DDS chip to excite alkali metal atoms in an atomic cell to generate two orthogonal reference signals for extracting phase information of a magnetic resonance signal; then, the magnetic resonance signal and the reference signal are simultaneously sent into an analog multiplier, and low-pass filtering is performed to extract the phase information of the magnetic resonance signal; then, phase compensation is performed to suppress phase lag and drift in the system; finally, PID control is performed to change the output frequency of the DDS chip to realize closed-loop control of the phase. The technical scheme of the application is used to solve the technical problem that the overall power consumption of the prior art is large and it is difficult to meet the application requirement of the atomic magnetometer in a low-power-consumption engineering environment.

Description

Technical Field

[0001] This invention relates to the field of quantum sensing technology, and in particular to a low-power, high-precision closed-loop control method and system for magnetic resonance signal phase. Background Technology

[0002] Alkali metal atomic magnetometers measure magnetic fields by utilizing the precession of electron spin or nuclear spin in a magnetic field. They have advantages such as high accuracy and small size, and are mainly used for measuring the Earth's magnetic field, measuring weak magnetic fields in organisms such as brain magnetocardiography and heart magnetocardiography, as well as underwater, surface and airborne target detection. They are of great significance in national economic construction and national defense.

[0003] When the atoms within the atomic chamber operate in a resonant state, the phase difference between the magnetic resonance signal and the reference excitation signal remains constant, resulting in the highest sensitivity and stability for the atomic magnetometer. Therefore, to ensure the accuracy of the atomic magnetometer's magnetic field measurement and improve its magnetic field manipulation performance, high-precision phase closed-loop control of the magnetic resonance signal is essential. Furthermore, given the increasing demands for endurance and other self-sufficiency requirements in small unmanned platforms such as anchor mine magnetic fuses, magnetic buoys, and underwater vehicles, the atomic magnetometer faces the challenge of achieving high accuracy with low power consumption.

[0004] Traditional magnetic resonance phase closed-loop control methods (such as CN114460506 B, magnetic resonance signal phase closed-loop control method and system based on variable parameter control) are implemented through digital demodulation methods using high-power devices such as high-speed ADCs, high-speed DACs and FPGAs. The overall power consumption of the system is relatively large, which makes it difficult to meet the application requirements of low-power engineering environments for atomic magnetometers. Summary of the Invention

[0005] This invention provides a low-power, high-precision closed-loop control method and system for the phase of magnetic resonance signals, which can solve the technical problem that the overall power consumption of existing systems is large and it is difficult to meet the application requirements of low-power engineering environments for atomic magnetometers.

[0006] According to one aspect of the present invention, a low-power, high-precision phase closed-loop control method for magnetic resonance signals is provided. The method includes: generating a magnetic field excitation signal and two reference signals with a phase difference of 90° using a DDS chip; multiplying the magnetic resonance signal with the two reference signals using an analog multiplier to obtain the output of the analog multiplier; performing low-pass filtering on the output to obtain two filtered outputs; acquiring the two filtered outputs using a low-power ADC chip; dividing and simplifying the two filtered outputs to obtain the phase difference between the magnetic resonance signal and the reference signal; and controlling the phase difference based on the magnetic resonance signal and the reference signals. The phase difference between the magnetic resonance signal and the magnetic field excitation signal is calculated. Phase compensation is performed on the phase difference between the magnetic resonance signal and the magnetic field excitation signal. The phase difference between the phase-compensated magnetic resonance signal and the magnetic field excitation signal is compared with the desired phase difference. The difference between the phase difference between the phase-compensated magnetic resonance signal and the magnetic field excitation signal and the desired phase difference is substituted into the PID closed-loop control algorithm to obtain the change in the frequency of the excitation signal. The output frequency of the DDS chip is changed until the phase difference between the phase-compensated magnetic resonance signal and the magnetic field excitation signal equals the desired phase difference, thus completing the phase closed-loop control of the magnetic resonance signal.

[0007] Furthermore, the magnetic field excitation signal x A The expression is x A =Asin(ωt+θ) A ), reference signal x B ,x C The expression is Where A is the amplitude of the magnetic field excitation signal, ω is the signal frequency, t is time, and θ is... A Let B be the phase of the magnetic field excitation signal, B be the signal amplitude, and θ be the... B θ C The phases of the two reference signals are 90° apart.

[0008] Furthermore, the expression for the magnetic resonance signal after atomic resonance within the atomic chamber is x. D =Dsin(ωt+θ) D ), where D is the magnetic resonance signal amplitude, ω is the signal frequency, t is time, and θ is... D This represents the phase of the magnetic resonance signal.

[0009] Furthermore, the output of the simulated multiplier is Y B Y C It is the output of the analog multiplier, which is the superposition of DC component and high-frequency AC component.

[0010] Furthermore, the two-channel filtered output result Y′ B 、Y′ CThe expression is

[0011] Furthermore, the phase difference between the magnetic resonance signal and the reference signal is θ. D -θ B =acot(Y).

[0012] Furthermore, the phase difference between the magnetic resonance signal and the magnetic field excitation signal is... Where, θ A-B The phase difference between the reference signal and the analog excitation signal can be determined by actual measurement and is a constant.

[0013] Furthermore, the phase difference between the phase-compensated magnetic resonance signal and the magnetic field excitation signal is θ = Φ(θ D-A ,T).

[0014] According to another aspect of the present invention, a low-power, high-precision magnetic resonance signal phase closed-loop control system is provided, which uses the low-power, high-precision magnetic resonance signal phase closed-loop control method described above to perform magnetic resonance signal phase closed-loop control.

[0015] Furthermore, the low-power, high-precision magnetic resonance signal phase closed-loop control system includes a DDS chip, an atomic gas cell, an analog multiplier, a low-pass filter, a low-power ADC chip, and a low-power ARM processor. The DDS chip generates the magnetic field excitation signal and two reference signals with a 90° phase difference. The analog multiplier multiplies the magnetic resonance signal output from the atomic gas cell with the two reference signals to obtain the output of the analog multiplier. The low-pass filter performs low-pass filtering on the output to obtain two filtered outputs. The low-power ADC chip acquires the two filtered outputs. The low-power ARM processor divides and simplifies the two filtered outputs to obtain the magnetic resonance signal and the reference signals. The phase difference between the magnetic resonance signal and the magnetic field excitation signal is calculated based on the phase difference between the magnetic resonance signal and the reference signal. Phase compensation is performed on the phase difference between the magnetic resonance signal and the magnetic field excitation signal. The phase difference between the phase-compensated magnetic resonance signal and the magnetic field excitation signal is compared with the desired phase difference. The difference between the phase difference between the phase-compensated magnetic resonance signal and the magnetic field excitation signal and the desired phase difference is substituted into the PID closed-loop control algorithm to obtain the change in the excitation signal frequency. The output frequency of the DDS chip is changed until the phase difference between the phase-compensated magnetic resonance signal and the magnetic field excitation signal equals the desired phase difference, thus completing the phase closed-loop control of the magnetic resonance signal.

[0016] The present invention provides a low-power, high-precision closed-loop phase control method for magnetic resonance signals. This method uses a low-power DDS chip to generate a magnetic field excitation signal, which excites alkali metal atoms in the atomic chamber, generating two orthogonal reference signals for extracting the phase information of the magnetic resonance signal. Then, the magnetic resonance signal and the reference signals are simultaneously fed into an analog multiplier and low-pass filtered to extract the phase information of the magnetic resonance signal. Phase compensation is then used to suppress phase hysteresis and drift within the system. Finally, PID control is used to change the output frequency of the DDS chip, achieving closed-loop phase control. Therefore, compared with existing technologies, the low-power, high-precision magnetic resonance signal phase closed-loop control method provided by this invention is based on analog multipliers, low-power DDS chips, ADC chips, and ARM processors. It builds and designs the hardware and software for magnetic resonance signal closed-loop control, significantly reducing system power consumption while ensuring high-precision phase control. Furthermore, it performs temperature compensation, suppressing temperature drift in analog demodulation, thereby improving the system's environmental adaptability, meeting the requirements of low-power engineering applications, realizing magnetic resonance signal phase closed-loop control, significantly reducing system power consumption, suppressing phase temperature drift, improving magnetic field measurement stability, and ensuring the system's environmental adaptability. Attached Figure Description

[0017] The accompanying drawings, which form part of this specification, are provided to further illustrate embodiments of the invention and, together with the textual description, explain the principles of the invention. It is obvious that the drawings described below are merely some embodiments of the invention, and those skilled in the art can obtain other drawings based on these drawings without any creative effort.

[0018] Figure 1 A schematic diagram of a low-power, high-precision magnetic resonance signal phase closed-loop control system according to a specific embodiment of the present invention is shown. Detailed Implementation

[0019] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0021] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the invention. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0022] like Figure 1 As shown, a low-power, high-precision phase closed-loop control method for magnetic resonance signals is provided according to a specific embodiment of the present invention. This method includes: generating a magnetic field excitation signal and two reference signals with a phase difference of 90° using a DDS chip; multiplying the magnetic resonance signal with the two reference signals using an analog multiplier to obtain the output of the analog multiplier; performing low-pass filtering on the output to obtain two filtered outputs; acquiring the two filtered outputs using a low-power ADC chip; dividing and simplifying the two filtered outputs to obtain the phase difference between the magnetic resonance signal and the reference signal; and controlling the phase difference based on the magnetic resonance signal... The phase difference between the magnetic resonance signal and the magnetic field excitation signal is calculated by measuring the phase difference between the signal and the reference signal. Phase compensation is then performed on the phase difference between the magnetic resonance signal and the magnetic field excitation signal. The phase difference between the phase-compensated magnetic resonance signal and the magnetic field excitation signal is compared with the desired phase difference. The difference between the phase difference between the phase-compensated magnetic resonance signal and the magnetic field excitation signal and the desired phase difference is substituted into the PID closed-loop control algorithm to obtain the change in the frequency of the excitation signal. The output frequency of the DDS chip is then changed until the phase difference between the phase-compensated magnetic resonance signal and the magnetic field excitation signal equals the desired phase difference, thus completing the phase closed-loop control of the magnetic resonance signal.

[0023] This configuration provides a low-power, high-precision closed-loop phase control method for magnetic resonance signals. The method involves a low-power DDS chip generating a magnetic field excitation signal to excite alkali metal atoms in the atomic chamber, producing two orthogonal reference signals for extracting the phase information of the magnetic resonance signal. The magnetic resonance signal and reference signals are then simultaneously fed into an analog multiplier and low-pass filtered to extract the phase information. Phase compensation is then used to suppress phase hysteresis and drift within the system. Finally, PID control is employed to change the output frequency of the DDS chip, achieving closed-loop phase control. Therefore, compared with existing technologies, the low-power, high-precision magnetic resonance signal phase closed-loop control method provided by this invention is based on analog multipliers, low-power DDS chips, ADC chips, and ARM processors. It builds and designs the hardware and software for magnetic resonance signal closed-loop control, significantly reducing system power consumption while ensuring high-precision phase control. Furthermore, it performs temperature compensation, suppressing temperature drift in analog demodulation, thereby improving the system's environmental adaptability, meeting the requirements of low-power engineering applications, realizing magnetic resonance signal phase closed-loop control, significantly reducing system power consumption, suppressing phase temperature drift, improving magnetic field measurement stability, and ensuring the system's environmental adaptability.

[0024] Specifically, this invention proposes a low-power, high-precision magnetic resonance signal phase closed-loop control method and device, including the construction of the hardware system and the implementation of the software algorithm, etc.

[0025] First, the DDS chip generates a magnetic field excitation signal to excite the alkali metal atoms in the atomic chamber, generating two orthogonal reference signals used to extract the phase information of the magnetic resonance signal. Then, the magnetic resonance signal and the reference signals are simultaneously fed into an analog multiplier and low-pass filtered to extract the phase information of the magnetic resonance signal. Next, phase compensation is used to suppress phase hysteresis and drift in the system. Finally, PID control is used to change the output frequency of the DDS chip to achieve closed-loop phase control.

[0026] The technical solution of this invention:

[0027] A low-power, high-precision magnetic resonance signal phase closed-loop control method and device, comprising at least analog demodulation and phase compensation.

[0028] (1) Generation of magnetic field excitation signal and reference signal

[0029] The magnetic field excitation signal and reference signal are generated by a DDS chip. DDS technology is relatively mature and will not be discussed further in this invention. The expression for the excitation signal is as follows:

[0030] x A =Asin(ωt+θ) A (1)

[0031] Where A is the signal amplitude, ω is the signal frequency, t is time, and θ is... A For phase.

[0032] The expression for the reference signal is as follows:

[0033]

[0034] Where B is the signal amplitude, ω is the signal frequency, t is time, and θ is... B θ C The phase is 90°.

[0035] (2) Phase simulation demodulation

[0036] The expression for the magnetic resonance signal after atomic resonance within the atomic gas chamber is as follows:

[0037] x D =Dsin(ωt+θ) D (3)

[0038] Where D is the signal amplitude, ω is the signal frequency, t is time, and θ is... D For phase.

[0039] By using an analog multiplier, multiplying the magnetic resonance signal equation (3) by the two reference signals equation (2) respectively, we can obtain:

[0040]

[0041] Among them, Y B Y C It is the output of the analog multiplier, which is the superposition of DC component and high-frequency AC component.

[0042] By low-pass filtering the output of the analog multiplier, we can obtain:

[0043]

[0044] The filtered result Y′ is acquired using a low-power ADC chip. B 、Y′ C And divide the two:

[0045]

[0046] From equation (2), we can see that θ B θ C Since the phase difference is 90°, the above equation can be simplified to:

[0047]

[0048] The phase difference between the magnetic resonance signal and the reference signal can be expressed as:

[0049] θ D -θ B =arccot(Y)(8)

[0050] The system needs to solve for the phase difference θ between the magnetic resonance signal equation (3) and the simulated excitation signal equation (1). D-A However, the reference signal and the analog excitation signal have different phases, i.e., θ A ≠θ B However, since the difference is constant, the final phase can be expressed as:

[0051]

[0052] Where, θ A-B The phase difference between the reference signal and the analog excitation signal can be determined by actual measurement and is a constant.

[0053] (3) Phase compensation

[0054] Because the analog multiplier output has a constant bias, and the bias drifts with changes in operating temperature, affecting the accuracy of phase calculation, compensation is required.

[0055] Phase drift is related to temperature T:

[0056] θ=Φ(θ D-A ,T) (10)

[0057] Where Φ is the relationship function between temperature and phase obtained through experimental calibration.

[0058] (4) PID closed-loop control

[0059] Compare the phase difference in equation (10) with the desired phase difference, substitute the difference into the PID closed-loop control algorithm to obtain the change in the frequency of the excitation signal, and change the output frequency of the DDS until the phase difference equals the desired phase difference, thereby realizing the phase closed-loop control of the system.

[0060] The advantages of this system compared to existing technologies are:

[0061] Phase closed-loop control of magnetic resonance signals was achieved, which significantly reduced system power consumption, suppressed phase temperature drift, improved the stability of magnetic field measurement, and ensured the system's environmental adaptability.

[0062] According to another aspect of the present invention, a low-power, high-precision magnetic resonance signal phase closed-loop control system is provided, which uses the low-power, high-precision magnetic resonance signal phase closed-loop control method described above to perform magnetic resonance signal phase closed-loop control.

[0063] This configuration provides a low-power, high-precision closed-loop control system for magnetic resonance signal phase. Based on an analog multiplier, a low-power DDS chip, an ADC chip, and an ARM processor, the system builds and designs the hardware and software for closed-loop control of the magnetic resonance signal. While ensuring high precision in phase control, it significantly reduces system power consumption and incorporates temperature compensation to suppress temperature drift in analog demodulation, thereby improving the system's environmental adaptability and meeting the requirements of low-power engineering applications. This achieves closed-loop phase control of the magnetic resonance signal, significantly reduces system power consumption, suppresses phase temperature drift, improves magnetic field measurement stability, and ensures the system's environmental adaptability.

[0064] Furthermore, in this invention, the low-power, high-precision magnetic resonance signal phase closed-loop control system includes a DDS chip, an atomic gas cell, an analog multiplier, a low-pass filter, a low-power ADC chip, and a low-power ARM processor. The DDS chip generates a magnetic field excitation signal and two reference signals with a phase difference of 90°. The analog multiplier multiplies the magnetic resonance signal output from the atomic gas cell with the two reference signals to obtain the output of the analog multiplier. The low-pass filter performs low-pass filtering on the output to obtain two filtered outputs. The low-power ADC chip acquires the two filtered outputs. The low-power ARM processor divides and simplifies the two filtered outputs to obtain the magnetic resonance signal. The phase difference between the magnetic resonance signal and the reference signal is used to calculate the phase difference between the magnetic resonance signal and the magnetic field excitation signal. Phase compensation is performed on the phase difference between the magnetic resonance signal and the magnetic field excitation signal. The phase difference between the phase-compensated magnetic resonance signal and the magnetic field excitation signal is compared with the desired phase difference. The difference between the phase difference between the phase-compensated magnetic resonance signal and the magnetic field excitation signal and the desired phase difference is substituted into the PID closed-loop control algorithm to obtain the change in the excitation signal frequency. The output frequency of the DDS chip is changed until the phase difference between the phase-compensated magnetic resonance signal and the magnetic field excitation signal equals the desired phase difference, thus completing the phase closed-loop control of the magnetic resonance signal.

[0065] In summary, this invention provides a low-power, high-precision closed-loop phase control method and system for magnetic resonance signals. First, a low-power DDS chip generates a magnetic field excitation signal to excite alkali metal atoms in the atomic chamber, generating two orthogonal reference signals used to extract the phase information of the magnetic resonance signal. Then, the magnetic resonance signal and the reference signals are simultaneously fed into an analog multiplier and low-pass filtered to extract the phase information of the magnetic resonance signal. Next, phase compensation is used to suppress phase hysteresis and drift within the system. Finally, PID control is used to change the output frequency of the DDS chip, achieving closed-loop phase control. This invention achieves closed-loop phase control of magnetic resonance signals, significantly reducing system power consumption, suppressing phase temperature drift, improving magnetic field measurement stability, and ensuring the system's environmental adaptability.

[0066] For ease of description, spatial relative terms such as "above," "on top of," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation beyond the orientation of the device as described in the figures. For example, if the device in the figures were inverted, a device described as "above" or "on top of" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0067] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore should not be construed as limiting the scope of protection of this invention.

[0068] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A low-power, high-precision phase closed-loop control method for magnetic resonance signals, characterized in that, The low-power, high-precision magnetic resonance signal phase closed-loop control method includes: The DDS chip generates a magnetic field excitation signal and two reference signals with a phase difference of 90°. The magnetic resonance signal is multiplied by two reference signals using an analog multiplier to obtain the output of the analog multiplier. The output is then low-pass filtered to obtain two filtered outputs. Two filtered outputs are acquired by a low-power ADC chip. The two filtered outputs are then divided and simplified to obtain the phase difference between the magnetic resonance signal and the reference signal. The phase difference between the magnetic resonance signal and the magnetic field excitation signal is calculated based on the phase difference between the magnetic resonance signal and the reference signal. Phase compensation is performed on the phase difference between the magnetic resonance signal and the magnetic field excitation signal; The phase difference between the phase-compensated magnetic resonance signal and the magnetic field excitation signal is compared with the desired phase difference. The difference between the phase difference between the phase-compensated magnetic resonance signal and the magnetic field excitation signal and the desired phase difference is substituted into the PID closed-loop control algorithm to obtain the change in the frequency of the excitation signal. The output frequency of the DDS chip is changed until the phase difference between the phase-compensated magnetic resonance signal and the magnetic field excitation signal is equal to the desired phase difference, thus completing the phase closed-loop control of the magnetic resonance signal.

2. The low-power, high-precision magnetic resonance signal phase closed-loop control method according to claim 1, characterized in that, The magnetic field excitation signal x A The expression is x A =Asin(ωt+θ) A The reference signal x B ,x C The expression is Where A is the amplitude of the magnetic field excitation signal, ω is the signal frequency, t is time, and θ is... A Let B be the phase of the magnetic field excitation signal, B be the signal amplitude, and θ be the... B θ C The phases of the two reference signals are 90° apart.

3. The low-power, high-precision magnetic resonance signal phase closed-loop control method according to claim 2, characterized in that, The expression for the magnetic resonance signal after atomic resonance in the atomic chamber is x. D =Dsin(ωt+θ) D ), where D is the magnetic resonance signal amplitude, ω is the signal frequency, t is time, and θ is... D This represents the phase of the magnetic resonance signal.

4. The low-power, high-precision magnetic resonance signal phase closed-loop control method according to claim 3, characterized in that, The output of the analog multiplier is: Y B Y C The output of the analog multiplier is the superposition of the DC component and the high-frequency AC component.

5. The low-power, high-precision magnetic resonance signal phase closed-loop control method according to claim 4, characterized in that, The two-channel filtered output result Y′ B 、Y′ C The expression is 6. The low-power, high-precision magnetic resonance signal phase closed-loop control method according to claim 5, characterized in that, The phase difference between the magnetic resonance signal and the reference signal is θ. D -θ B =acot(Y), where Y is the output of the two-channel filtering, Y′ B and Y′ C The ratio of .

7. The low-power, high-precision magnetic resonance signal phase closed-loop control method according to claim 6, characterized in that, The phase difference between the magnetic resonance signal and the magnetic field excitation signal is Where, θ A-B The phase difference between the reference signal and the analog excitation signal can be determined by actual measurement and is a constant.

8. The low-power, high-precision magnetic resonance signal phase closed-loop control method according to claim 7, characterized in that, The phase difference between the phase-compensated magnetic resonance signal and the magnetic field excitation signal is θ = Φ(θ D-A ,T), where T is the temperature.

9. A low-power, high-precision magnetic resonance signal phase closed-loop control system, characterized in that, The low-power, high-precision magnetic resonance signal phase closed-loop control system uses the low-power, high-precision magnetic resonance signal phase closed-loop control method as described in any one of claims 1 to 8 to perform magnetic resonance signal phase closed-loop control.

10. The low-power, high-precision magnetic resonance signal phase closed-loop control system according to claim 9, characterized in that, The low-power, high-precision magnetic resonance signal phase closed-loop control system includes a DDS chip, an atomic gas cell, an analog multiplier, a low-pass filter, a low-power ADC chip, and a low-power ARM processor. The DDS chip is used to generate a magnetic field excitation signal and two reference signals with a phase difference of 90°. The analog multiplier is used to multiply the magnetic resonance signal output from the atomic gas cell with the two reference signals to obtain the output result of the analog multiplier. The low-pass filter is used to perform low-pass filtering on the output result to obtain two filtered output results. The low-power ADC chip is used to acquire the two filtered output results. The low-power ARM processor is used to divide and simplify the two filtered outputs to obtain the phase difference between the magnetic resonance signal and the reference signal. Based on the phase difference between the magnetic resonance signal and the reference signal, the phase difference between the magnetic resonance signal and the magnetic field excitation signal is calculated. Phase compensation is performed on the phase difference between the magnetic resonance signal and the magnetic field excitation signal. The phase difference between the phase-compensated magnetic resonance signal and the magnetic field excitation signal is compared with the desired phase difference. The difference between the phase difference between the phase-compensated magnetic resonance signal and the magnetic field excitation signal and the desired phase difference is substituted into the PID closed-loop control algorithm to obtain the change in the excitation signal frequency. The output frequency of the DDS chip is changed until the phase difference between the phase-compensated magnetic resonance signal and the magnetic field excitation signal equals the desired phase difference, thus completing the phase closed-loop control of the magnetic resonance signal.

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