Closed-loop tracking measurement system and method for magnetic field intensity

Abstract

The invention provides a closed-loop tracking measurement system and method for magnetic field intensity, and relates to the technical field of atom magnetometer measurement, and the system comprises a dispersion signal acquisition module, a PID controller, a calculation module, a superposition module, a signal generator and a radio frequency source with a frequency modulation function. The dispersion signal acquisition module acquires a dispersion signal and sends the dispersion signal to the PID controller; the PID controller generates a PID output signal according to the dispersion signal with the purpose of driving the amplitude of the dispersion signal to return to zero, and sends the PID output signal to the superposition module; the signal generator sends a reference scanning signal to the superposition module; the superposition module superposes the reference scanning signal and the PID output signal to obtain a sum signal and sends the sum signal to the radio frequency source; and the radio frequency source modulates the frequency of the radio frequency signal output to the dispersion signal acquisition module according to the sum signal. The measuring range of the magnetic field intensity can be expanded, the measuring precision and the long-term stability are improved, and meanwhile the hardware circuit complexity and the power consumption of the measuring system are considered.

Description

Technical Field

[0001] This invention relates to the field of atomic magnetometer measurement technology, specifically to a closed-loop tracking measurement system and method for magnetic field strength. Background Technology

[0002] Coherent Population Trapping (CPT) magnetometer closed-loop tracking measurement technology is a highly sensitive magnetic field measurement method based on the interaction between atomic hyperfine structures and magnetic fields. It is widely used in precision navigation, geomagnetic surveying, and fundamental physics research. This technology utilizes the CPT effect: when the frequency difference of two coherent laser beams precisely matches the splitting point of the hyperfine level of an atom's ground state, the atom is prepared into a "dark state" that does not absorb light, thus minimizing laser absorption. An external magnetic field alters the splitting point of the energy levels through the Zeeman effect, causing a shift in the CPT resonant frequency. The error signal is extracted by frequency modulation of the radio frequency source, and this signal is used to construct a closed-loop control, thereby dynamically locking the CPT resonant frequency and ultimately converting it into magnetic field strength.

[0003] Existing technology employs a VCO (Voltage-Controlled Oscillator) + PID (Proportional-Integral-Derivative) to achieve closed-loop tracking measurement of magnetic field strength. Specifically, the PID controller processes the atomic resonance spectral line error signal and outputs a control voltage to the VCO, dynamically adjusting its radio frequency output frequency to accurately track the zero-crossing position of the CPT dispersion signal. When the radio frequency is locked at this zero-crossing point, its frequency value has a linear relationship with the magnetic field strength, thereby achieving continuous tracking and measurement of the magnetic field.

[0004] However, because VCOs typically have a narrow frequency adjustment range, and the linear relationship between frequency and input voltage is poor within this range, the VCO cannot provide sufficient frequency compensation when the external magnetic field changes significantly, leading to system lockout and severely limiting the dynamic measurement range of the magnetometer. Secondly, the VCO's output frequency is sensitive to environmental factors such as temperature changes, mechanical vibration, and device aging, easily causing frequency drift. This drift directly leads to inaccurate CPT resonance point locking, reducing the accuracy and long-term stability of magnetic field strength measurement. Furthermore, to overcome the shortcomings of VCOs, some solutions attempt to use more complex direct digital frequency synthesis circuits or phase-locked loop circuits, but this significantly increases the complexity and power consumption of the hardware system, hindering the miniaturization of the magnetometer and its application in low-power scenarios.

[0005] Therefore, how to expand the measurement range of magnetic field strength, improve measurement accuracy and long-term stability, while taking into account the complexity and power consumption of the measurement system's hardware circuits, has become an urgent technical problem to be solved. Summary of the Invention

[0006] In view of this, in order to solve the above-mentioned technical problems, the present invention provides a closed-loop tracking measurement system and method for magnetic field strength.

[0007] The present invention adopts the following technical solution: In a first aspect, the present invention provides a closed-loop tracking measurement system for magnetic field strength, comprising: a dispersive signal acquisition module, a PID controller, a calculation module, a superposition module, a signal generator, and a radio frequency source with frequency modulation function; The dispersion signal acquisition module is used to acquire the dispersion signal and send the dispersion signal to the PID controller; the dispersion signal is used to reflect the CPT resonant frequency shift caused by the influence of the magnetic field strength of the magnetic field environment under test. The PID controller generates a PID output signal based on the dispersion signal, with the aim of driving the amplitude of the dispersion signal to zero, and sends the PID output signal to the superposition module and the calculation module. The calculation module is used to calculate the magnetic field strength of the magnetic field environment to be measured based on the PID output signal; The signal generator is used to send a reference scan signal to the overlay module; The superposition module is used to superimpose the reference scan signal and the PID output signal to obtain a sum signal, and send the sum signal to the radio frequency source; The radio frequency source is used to modulate the frequency of the radio frequency signal it outputs to the dispersive signal acquisition module according to the sum signal, so that the amplitude of the dispersive signal is reduced to zero.

[0008] Optionally, the dispersive signal acquisition module includes: a laser, an electro-optical tuner, an alkali metal gas cell, a photoelectric receiving module, and a lock-in amplifier; the alkali metal gas cell is placed in the magnetic field environment to be measured. The laser is used to emit laser light of a specific wavelength to the electro-optical debugger; The electro-optic debugger receives the radio frequency signal output by the radio frequency source and uses the radio frequency signal to debug the laser it receives, generating double-sideband multicolor light; The double-sideband multicolor light passes through the alkali metal gas cell and strikes the photoelectric receiving module; wherein, the transmittance of the alkali metal gas cell is maximized when the frequency difference between the two sidebands of the double-sideband multicolor light matches the CPT resonant frequency of the alkali metal gas cell. The photoelectric receiving module is used to convert the received double-sideband multicolor light into a voltage signal and output the voltage signal to the lock-in amplifier; The lock-in amplifier uses the reference signal sent by the signal generator to demodulate the voltage signal to obtain a dispersion signal, and then sends the dispersion signal to the PID controller.

[0009] Optionally, the photoelectric receiving module includes a photodetector and a transimpedance amplifier; The photodetector is used to receive the double-sideband multicolor light, convert the double-sideband multicolor light into a current signal, and send the current signal to the transimpedance amplifier; The transimpedance amplifier is used to convert the current signal into the voltage signal.

[0010] Optionally, the photodetector is a photodiode.

[0011] Optionally, the superposition module is an analog adder constructed using an operational amplifier.

[0012] Optionally, the overlay module includes an analog-to-digital converter, a digital adder, and a digital-to-analog converter; The analog-to-digital converter is used to convert the reference scan signal into a first digital signal and the PID output signal into a second digital signal; The digital adder is used to superimpose the first digital signal and the second digital signal to obtain a third digital signal; The digital-to-analog converter is used to perform digital-to-analog conversion on the third digital signal to obtain the sum signal.

[0013] Secondly, the present invention provides a closed-loop tracking measurement method for magnetic field strength, applied to the closed-loop tracking measurement system for magnetic field strength as described above, the closed-loop tracking measurement method for magnetic field strength comprising: The dispersion signal acquisition module acquires the dispersion signal and sends the dispersion signal to the PID controller; the dispersion signal is used to reflect the CPT resonant frequency shift caused by the influence of the magnetic field strength of the magnetic field environment under test; The PID controller generates a PID output signal based on the dispersion signal, with the aim of driving the amplitude of the dispersion signal to zero, and sends the PID output signal to the superposition module and the calculation module. The calculation module calculates the magnetic field strength of the magnetic field environment to be measured based on the PID output signal; The signal generator sends a reference scan signal to the superposition module; The superposition module superimposes the reference scan signal and the PID output signal to obtain a sum signal, and sends the sum signal to the radio frequency source; The radio frequency source modulates the frequency of the radio frequency signal it outputs to the dispersive signal acquisition module according to the sum signal, so that the amplitude of the dispersive signal is reduced to zero.

[0014] Optionally, the dispersive signal acquisition module includes: a laser, an electro-optical tuner, an alkali metal gas cell, a photoelectric receiving module, and a lock-in amplifier; the alkali metal gas cell is placed in the magnetic field environment to be measured. The dispersive signal acquisition module acquires the dispersive signal, specifically including: The laser emits a laser of a specific wavelength to the electro-optical tuner; The electro-optic debugger receives the radio frequency signal output by the radio frequency source and uses the radio frequency signal to debug the laser it receives, generating double-sideband multicolor light; The double-sideband multicolor light passes through the alkali metal gas cell and strikes the photoelectric receiving module; wherein, the transmittance of the alkali metal gas cell is maximized when the frequency difference between the two sidebands of the double-sideband multicolor light matches the CPT resonant frequency of the alkali metal gas cell. The photoelectric receiving module converts the received double-sideband multicolor light into a voltage signal and outputs the voltage signal to the lock-in amplifier; The lock-in amplifier uses the reference signal sent by the signal generator to demodulate the voltage signal to obtain a dispersive signal.

[0015] This invention employs the above technical solutions. First, by combining the frequency modulation function of the superposition module and the RF source, the traditional VCO is replaced, eliminating the inherent narrow frequency adjustment range limitation of the VCO. The frequency offset compensation range can be flexibly set by configuring the frequency modulation offset parameters of the RF source through software, thereby covering and tracking a wider range of magnetic field changes and greatly expanding the magnetic field strength measurement range. Second, by eliminating the VCO, the frequency drift problem caused by environmental factors such as temperature changes, mechanical vibration, and device aging is fundamentally avoided, thus improving measurement accuracy and long-term stability. Finally, due to the simple structure of the superposition module and the RF source, this invention can balance the hardware circuit complexity and power consumption of the measurement system. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1This is a schematic diagram of the structure of a closed-loop tracking measurement system for magnetic field strength provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of the tracking curve for the zero-crossing point in a crystal oscillator closed-loop scheme provided in an embodiment of the present invention; Figure 3 This is a schematic diagram of the tracking curve for zero crossings in an adder closed-loop scheme provided by an embodiment of the present invention; Figure 4 This is a schematic flowchart of a closed-loop tracking measurement method for magnetic field strength provided in an embodiment of the present invention. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0019] Figure 1 This is a schematic diagram of a closed-loop tracking measurement system for magnetic field strength provided in an embodiment of the present invention. Figure 1 As shown, the closed-loop tracking measurement system for this magnetic field strength includes: a dispersion signal acquisition module, a PID controller 11, and a calculation module ( Figure 1 (Not shown in the image), superposition module 12, signal generator 13, and radio frequency source 14 with frequency modulation function.

[0020] The dispersion signal acquisition module is used to acquire the dispersion signal and send the dispersion signal to the PID controller 11; the dispersion signal is used to reflect the CPT resonance frequency shift caused by the influence of the magnetic field strength of the magnetic field environment under test.

[0021] Specifically, the dispersive signal acquisition module may include: a laser 15, an electro-optical debugger 16, an alkali metal gas cell 17, a photoelectric receiving module, and a lock-in amplifier 110. The alkali metal gas cell is placed in the magnetic field environment to be measured.

[0022] Laser 15 is used to emit laser light of a specific wavelength to electro-optic tuner 16. Laser 15 can be a distributed Bragg reflector laser or a vertical cavity surface emitter laser, the output wavelength of which is precisely tuned to the D1 or D2 absorption line of alkali metal atoms (such as rubidium or cesium atoms).

[0023] The laser emitted by laser 15 passes through an optical fiber and an optical fiber coupler ( Figure 1(Using two fiber optic couplers as an example) The laser enters the electro-optical debugger 16. The electro-optical debugger 16 receives the radio frequency signal output from the radio frequency source 14 and uses the radio frequency signal to debug the received laser, generating double-sideband multicolor light.

[0024] After passing through the alkali metal gas cell 17, the double-sideband multicolor light strikes the photoelectric receiving module. When the frequency difference between the two sidebands of the double-sideband multicolor light matches the CPT resonance frequency of the alkali metal gas cell (i.e., the Raman transition frequency between the two ground hyperfine energy levels of the alkali metal atom splitting under the action of a magnetic field), the atom is pumped into a coherent population trapped state, and the transmittance of the alkali metal gas cell is maximized.

[0025] The photoelectric receiving module converts the received double-sideband multicolor light into a voltage signal and outputs the voltage signal to the lock-in amplifier 110. Specifically, the photoelectric receiving module may include a photodetector 18 and a transimpedance amplifier 19. The photodetector 18 may be a photodiode. The photodetector 18 receives the double-sideband multicolor light, converts it into a current signal, and sends the current signal to the transimpedance amplifier 19. The transimpedance amplifier 19 converts the current signal into a voltage signal.

[0026] To perform phase-locked demodulation, signal generator 13 generates a low-frequency sinusoidal modulation signal (e.g., 10kHz). This signal is split into two paths: one path is sent as a reference signal to lock-in amplifier 110, and the other path is sent as a reference scan signal to superposition module 12. Lock-in amplifier 110 uses the reference signal sent by signal generator 13 to demodulate the voltage signal, obtaining a dispersive signal, and sends the dispersive signal to PID controller 11. The amplitude of the dispersive signal reflects the offset between the CPT resonance peak center and the sideband frequency difference of the double-sideband polychromatic light, and the polarity of the dispersive signal reflects the offset direction between the CPT resonance peak center and the sideband frequency difference of the double-sideband polychromatic light. When the sideband frequency difference is exactly equal to the CPT resonance frequency, the amplitude of the dispersive signal is zero; when the sideband frequency difference deviates from the CPT resonance frequency, the amplitude of the dispersive signal is non-zero.

[0027] The PID controller 11 generates a PID output signal based on the dispersion signal, aiming to drive the amplitude of the dispersion signal to zero, and sends the PID output signal to the superposition module 12 and the calculation module. Specifically, the PID controller 11 has a preset operating point internally. In closed-loop tracking applications, the preset operating point is usually set to zero voltage, corresponding to the zero-crossing point of the dispersion signal, i.e., the CPT resonance center. The PID controller 11 compares the deviation between the input dispersion signal and the preset operating point in real time, and performs proportional, integral, and derivative operations based on this deviation to generate the PID output signal.

[0028] The calculation module is used to calculate the magnetic field strength of the environment under test based on the PID output signal. Specifically, in a stable closed-loop locked state, the change in the external magnetic field is proportional to the offset of the CPT resonant frequency. Correspondingly, to compensate for this frequency offset, the amplitude of the output signal of the PID controller 11 must also correspond to it. Therefore, by using a pre-calibrated proportional coefficient, the real-time change in magnetic field strength can be accurately calculated based on the value of the PID output signal monitored and recorded in real time.

[0029] The superposition module 12 is used to superimpose the reference scan signal and the PID output signal to obtain the sum signal, and then send the sum signal to the RF source 14.

[0030] The radio frequency source 14 is used to modulate the frequency of the radio frequency signal output to the dispersion signal acquisition module according to the signal. The adjusted radio frequency signal then acts on the electro-optic debugger 16 to change the frequency interval of the laser sideband, thereby pulling the CPT resonance point back to the locked position, so that the amplitude of the dispersion signal is always kept near zero, thus forming a stable and accurate CPT resonance frequency closed-loop tracking circuit.

[0031] It should be noted that some preparatory steps are required before closed-loop measurement: First, the system is calibrated to determine optimal operating parameters. Specifically, a magnetic field along the laser direction is applied around the alkali metal chamber 17, and the PID controller 11 is temporarily set to open-loop mode. A sinusoidal modulation signal (reference signal) is input to the lock-in amplifier 110, and a specific scanning signal, such as a periodic triangular scanning voltage, is input to the superposition module 12. This triangular wave signal is directly fed into the RF source through the superposition module, causing the frequency of the RF signal output by the RF source to linearly reciprocate around a center frequency. As the frequency scans, the lock-in amplifier outputs a complete, periodic CPT dispersion signal. The operator observes the waveform of this dispersion signal using an oscilloscope and adjusts the center frequency of the RF source and the maximum frequency modulation offset to ensure that the zero-crossing point of a selected, magnetically sensitive CPT dispersion signal is precisely located at the center of the triangular wave scanning period T (peak / valley value). This step ensures that the center point of the closed-loop lock is perfectly aligned with the center of the resonance peak.

[0032] After calibration, the locking phase begins. The signal sent from the signal generator to the superposition module is switched from a triangular wave to a sinusoidal modulation signal for phase-locked demodulation (i.e., the reference scan signal, consistent with the sinusoidal modulation signal input to the lock-in amplifier 110). At this time, since the frequency of the RF signal is set near the CPT resonant point, the output (dispersion signal) of the lock-in amplifier will have a DC value close to zero. This DC voltage value is accurately recorded and set as the preset operating point of the PID controller.

[0033] This invention employs the above technical solutions. First, by combining a superposition module with the frequency modulation function of an RF source, it replaces the traditional VCO, eliminating the inherent narrow frequency adjustment range limitation of the VCO. The frequency offset compensation range can be flexibly set through software configuration of the RF source's frequency modulation offset parameters, supporting rapid compensation on the MHz scale. This allows for the coverage and tracking of a wider range of magnetic field changes, significantly expanding the magnetic field strength measurement range. Second, by eliminating the VCO, the frequency drift problem caused by environmental factors such as temperature changes, mechanical vibration, and device aging is fundamentally avoided, thereby improving measurement accuracy and long-term stability. Finally, the simple structure of the superposition module and RF source allows this invention to balance the complexity of the measurement system's hardware circuitry and power consumption.

[0034] In a specific example, the superposition module 12 can be an analog adder constructed using a zero-temperature-drift, high-precision operational amplifier. Because analog adders have extremely high response speeds and extremely low signal processing delays, the delay of the entire feedback loop is very small, making them particularly suitable for applications requiring high bandwidth and real-time tracking of rapidly changing magnetic fields. At the same time, analog adders are simple in structure and low in cost, and by selecting high-precision components, they can ensure excellent linearity and accuracy in signal superposition, thus maintaining the aforementioned advantages of wide measurement range and high stability.

[0035] In another specific example, the overlay module 12 may also include an analog-to-digital converter, a digital adder, and a digital-to-analog converter.

[0036] An analog-to-digital converter is used to convert a reference scan signal into a first digital signal and a PID output signal into a second digital signal.

[0037] A digital adder is used to superimpose a first digital signal and a second digital signal to obtain a third digital signal.

[0038] A digital-to-analog converter is used to convert a third digital signal into an analog signal, resulting in a sum signal.

[0039] To further illustrate the advantages of the adder's closed-loop design, the inventors built two closed-loop measurement systems: one using a crystal oscillator-based closed-loop scheme (referencing patent application CN117890834A), and the other using an adder-based closed-loop scheme. A coil capable of generating a specific magnetic field was also fabricated. After calibration, the rate of change of the magnetic field strength generated by the coil with current was measured to be 120 nT / mA.

[0040] Figure 2 This is a schematic diagram of the zero-crossing tracking curve in a crystal oscillator closed-loop scheme provided in an embodiment of the present invention. Figure 2As shown, this illustrates the change in the demodulated output value of the lock-in amplifier in a closed-loop crystal oscillator scheme (i.e., in the existing technology) when the magnetic field changes. Each transition in the demodulated output value corresponds to a 0.1mA increase in coil current, which is equivalent to a 12nT increase in magnetic field strength. The entire closed-loop test process adds a total of 0.6mA of current (corresponding to 6 transitions). From Figure 2 As can be seen, when the coil current increases by 0.5mA (corresponding to a 60T magnetic field increment), the PID closed loop can still pull the demodulated output value back to the lock point. However, when the coil current increases by 0.6mA, the demodulated output value cannot return to the lock point, and the system loses lock. In other words, the measurable magnetic field change range of the system is only 120nT.

[0041] Figure 3 This is a schematic diagram of the tracking curve for zero-crossing points in an adder closed-loop scheme provided by an embodiment of the present invention. Figure 3 As shown, this illustrates the change in the demodulated output value of the lock-in amplifier when the magnetic field changes in the closed-loop scheme of the adder (i.e., the technical solution of this application). Each transition corresponds to a 10mA increase in coil current, which is equivalent to a 1200nT increase in magnetic field strength. The entire closed-loop test process adds a total of 100mA of current (corresponding to 10 transitions). From Figure 3 As can be seen, when the coil current increases by 90mA (corresponding to a magnetic field increment of 10800nT, the 9th transition), the PID closed-loop can still pull the demodulated output value back to the lock point. However, when the coil current increases by 100mA (corresponding to the 10th transition), the demodulated output value cannot return to the lock point, and the system loses lock. This means the system can measure magnetic field changes within a range of 21600nT. However, in this adder closed-loop measurement, the maximum frequency deviation of the RF source was set to 100kHz, and the PID output was limited to between -1 and +1V. If the maximum frequency deviation is set to 200kHz or higher, and the PID output is limited to between -2 and +2V, the magnetic field measurement range of the system will double.

[0042] Based on a general inventive concept, the present invention also provides a closed-loop tracking measurement method for magnetic field strength. Figure 4 This is a schematic flowchart of a closed-loop tracking measurement method for magnetic field strength provided in an embodiment of the present invention. This closed-loop tracking measurement method for magnetic field strength is applied to the closed-loop tracking measurement system for magnetic field strength as described above. Figure 4 As shown, the closed-loop tracking measurement method for this magnetic field strength includes: Step 401: The dispersion signal acquisition module acquires the dispersion signal and sends it to the PID controller; the dispersion signal is used to reflect the CPT resonant frequency shift caused by the influence of the magnetic field strength of the magnetic field environment under test.

[0043] Step 402: The PID controller generates a PID output signal based on the dispersion signal, with the aim of driving the amplitude of the dispersion signal to zero, and sends the PID output signal to the superposition module and the calculation module.

[0044] Step 403: The calculation module calculates the magnetic field strength of the magnetic field environment to be measured based on the PID output signal.

[0045] Step 404: The signal generator sends a reference scan signal to the overlay module.

[0046] Step 405: The superposition module superimposes the reference scan signal and the PID output signal to obtain the sum signal, and sends the sum signal to the RF source.

[0047] Step 406: The RF source modulates the frequency of the RF signal it outputs to the dispersive signal acquisition module according to the signal, so that the amplitude of the dispersive signal is reduced to zero.

[0048] Optionally, the dispersive signal acquisition module includes: a laser, an electro-optical debugger, an alkali metal gas cell, a photoelectric receiving module, and a lock-in amplifier; the alkali metal gas cell is placed in the magnetic field environment to be measured.

[0049] The dispersive signal acquisition module acquires the dispersive signal, and may specifically include: (1) The laser emits a laser of a specific wavelength to the electro-optical tuner.

[0050] (2) The electro-optical debugger receives the radio frequency signal output by the radio frequency source and uses the radio frequency signal to debug the laser it receives, thereby generating double-sideband multicolor light.

[0051] (3) After passing through the alkali metal gas cell, the double-sideband multicolor light hits the photoelectric receiving module; among them, the transmittance of the alkali metal gas cell is the largest when the frequency difference between the two sidebands of the double-sideband multicolor light matches the CPT resonant frequency of the alkali metal gas cell.

[0052] (4) The photoelectric receiving module converts the double-sideband multicolor light it receives into a voltage signal and outputs the voltage signal to the lock-in amplifier.

[0053] (5) The lock-in amplifier uses the reference signal sent by the signal generator to demodulate the voltage signal and obtain the dispersive signal.

[0054] It is understood that the same or similar parts in the above embodiments can be referred to each other, and the contents not described in detail in some embodiments can be referred to the same or similar contents in other embodiments.

[0055] It should be noted that in the description of this invention, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance. Furthermore, in the description of this invention, unless otherwise stated, "a plurality of" means at least two.

[0056] Any process or method described in the flowchart or otherwise herein can be understood as representing a module, segment, or portion of code comprising one or more executable instructions for implementing a particular logical function or process, and the scope of preferred embodiments of the invention includes additional implementations in which functions may be performed not in the order shown or discussed, including substantially simultaneously or in reverse order depending on the functions involved, as will be understood by those skilled in the art to which embodiments of the invention pertain.

[0057] It should be understood that various parts of the present invention can be implemented in hardware, software, firmware, or a combination thereof. In the above embodiments, multiple steps or methods can be implemented in software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, it can be implemented using any one or a combination of the following techniques known in the art: discrete logic circuits having logic gates for implementing logical functions on data signals, application-specific integrated circuits (ASICs) having suitable combinational logic gates, programmable gate arrays (PGAs), field-programmable gate arrays (FPGAs), etc.

[0058] Those skilled in the art will understand that all or part of the steps of the methods in the above embodiments can be implemented by a program instructing related hardware. The program can be stored in a computer-readable storage medium, and when executed, the program includes one or a combination of the steps of the method embodiments.

[0059] Furthermore, the functional units in the various embodiments of the present invention can be integrated into a processing module, or each unit can exist physically separately, or two or more units can be integrated into a module. The integrated module can be implemented in hardware or as a software functional module. If the integrated module is implemented as a software functional module and sold or used as an independent product, it can also be stored in a computer-readable storage medium.

[0060] The storage media mentioned above can be read-only memory, disk, or optical disk, etc.

[0061] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0062] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A closed-loop tracking measurement system for magnetic field strength, characterized in that, include: The system includes a dispersive signal acquisition module, a PID controller, a calculation module, a superposition module, a signal generator, and an RF source with frequency modulation function. The dispersion signal acquisition module is used to acquire the dispersion signal and send the dispersion signal to the PID controller; the dispersion signal is used to reflect the CPT resonance frequency shift caused by the influence of the magnetic field strength of the magnetic field environment under test. The PID controller generates a PID output signal based on the dispersion signal, with the aim of driving the amplitude of the dispersion signal to zero, and sends the PID output signal to the superposition module and the calculation module. The calculation module is used to calculate the magnetic field strength of the magnetic field environment to be measured based on the PID output signal; The signal generator is used to send a reference scan signal to the overlay module; The superposition module is used to superimpose the reference scan signal and the PID output signal to obtain a sum signal, and send the sum signal to the radio frequency source; The radio frequency source is used to modulate the frequency of the radio frequency signal it outputs to the dispersive signal acquisition module according to the sum signal, so that the amplitude of the dispersive signal is reduced to zero.

2. The closed-loop tracking measurement system for magnetic field strength according to claim 1, characterized in that, The dispersive signal acquisition module includes: a laser, an electro-optical tuner, an alkali metal gas cell, a photoelectric receiving module, and a lock-in amplifier; the alkali metal gas cell is placed in the magnetic field environment to be measured. The laser is used to emit laser light of a specific wavelength to the electro-optical debugger; The electro-optic debugger receives the radio frequency signal output by the radio frequency source and uses the radio frequency signal to debug the laser it receives, generating double-sideband multicolor light; The double-sideband multicolor light passes through the alkali metal gas cell and strikes the photoelectric receiving module; wherein, the transmittance of the alkali metal gas cell is maximized when the frequency difference between the two sidebands of the double-sideband multicolor light matches the CPT resonant frequency of the alkali metal gas cell. The photoelectric receiving module is used to convert the received double-sideband multicolor light into a voltage signal and output the voltage signal to the lock-in amplifier; The lock-in amplifier uses the reference signal sent by the signal generator to demodulate the voltage signal to obtain a dispersion signal, and then sends the dispersion signal to the PID controller.

3. The closed-loop tracking measurement system for magnetic field strength according to claim 2, characterized in that, The photoelectric receiving module includes a photodetector and a transimpedance amplifier; The photodetector is used to receive the double-sideband multicolor light, convert the double-sideband multicolor light into a current signal, and send the current signal to the transimpedance amplifier; The transimpedance amplifier is used to convert the current signal into the voltage signal.

4. The closed-loop tracking measurement system for magnetic field strength according to claim 3, characterized in that, The photodetector is a photodiode.

5. The closed-loop tracking measurement system for magnetic field strength according to claim 1, characterized in that, The superposition module is an analog adder constructed using an operational amplifier.

6. The closed-loop tracking measurement system for magnetic field strength according to claim 1, characterized in that, The overlay module includes an analog-to-digital converter, a digital adder, and a digital-to-analog converter; The analog-to-digital converter is used to convert the reference scan signal into a first digital signal and the PID output signal into a second digital signal; The digital adder is used to superimpose the first digital signal and the second digital signal to obtain a third digital signal; The digital-to-analog converter is used to perform digital-to-analog conversion on the third digital signal to obtain the sum signal.

7. A closed-loop tracking measurement method for magnetic field strength, characterized in that, A closed-loop tracking measurement system for magnetic field strength as described in any one of claims 1 to 6, wherein the closed-loop tracking measurement method for magnetic field strength comprises: The dispersion signal acquisition module acquires the dispersion signal and sends the dispersion signal to the PID controller; the dispersion signal is used to reflect the CPT resonant frequency shift caused by the influence of the magnetic field strength of the magnetic field environment under test; The PID controller generates a PID output signal based on the dispersion signal, with the aim of driving the amplitude of the dispersion signal to zero, and sends the PID output signal to the superposition module and the calculation module. The calculation module calculates the magnetic field strength of the magnetic field environment to be measured based on the PID output signal; The signal generator sends a reference scan signal to the superposition module; The superposition module superimposes the reference scan signal and the PID output signal to obtain a sum signal, and sends the sum signal to the radio frequency source; The radio frequency source modulates the frequency of the radio frequency signal it outputs to the dispersive signal acquisition module according to the sum signal, so that the amplitude of the dispersive signal is reduced to zero.

8. The closed-loop tracking measurement method for magnetic field strength according to claim 7, characterized in that, The dispersive signal acquisition module includes: a laser, an electro-optical tuner, an alkali metal gas cell, a photoelectric receiving module, and a lock-in amplifier; the alkali metal gas cell is placed in the magnetic field environment to be measured. The dispersive signal acquisition module acquires the dispersive signal, specifically including: The laser emits a laser of a specific wavelength to the electro-optical tuner; The electro-optic debugger receives the radio frequency signal output by the radio frequency source and uses the radio frequency signal to debug the laser it receives, generating double-sideband multicolor light; The double-sideband multicolor light passes through the alkali metal gas cell and strikes the photoelectric receiving module; wherein, the transmittance of the alkali metal gas cell is maximized when the frequency difference between the two sidebands of the double-sideband multicolor light matches the CPT resonant frequency of the alkali metal gas cell. The photoelectric receiving module converts the received double-sideband multicolor light into a voltage signal and outputs the voltage signal to the lock-in amplifier; The lock-in amplifier uses the reference signal sent by the signal generator to demodulate the voltage signal to obtain a dispersive signal.

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