Free precession type vector atom magnetometer excitation measurement system based on FPGA

Abstract

The invention discloses a free precession type vector atom magnetometer excitation measurement system based on an FPGA (Field Programmable Gate Array), which belongs to the technical field of magnetic field measurement and comprises a laser unit, the laser unit is connected with an atom magnetometer probe and an optical pulse excitation unit, and a three-axis magnetic modulation excitation unit is connected with the atom magnetometer probe through a three-axis magnetic field coil. The three-axis modulation coils are installed in the X direction, the Y direction and the Z direction of the atomic magnetometer probe respectively. The magnetic pulse excitation unit is connected with an atom magnetometer probe through an excitation coil, and the atom magnetometer probe is connected with the triaxial vector free precession signal acquisition and processing unit; the three-axis magnetic modulation excitation unit, the magnetic pulse excitation unit, the optical pulse excitation unit and the three-axis vector free precession signal acquisition and processing unit are all in interactive connection with the upper computer; the free precession type vector atom magnetometer excitation measurement system based on the FPGA has the advantages of being good in real-time performance, simple in hardware structure, easy to integrate and low in cost.

Description

Technical Field

[0001] The present invention relates to the technical field of magnetic field measurement, and in particular to an FPGA-based free precession vector atomic magnetometer excitation measurement system. Background Art

[0002] Vector measurement of magnetic fields can obtain a lot of useful information and is of great significance for promoting scientific and technological progress and improving production efficiency. With the development of quantum precision measurement, atomic magnetometers have emerged. Their widespread application in the field of magnetic field vector measurement has spawned the development direction of high performance, miniaturization, and low cost. The free-precession vector atomic magnetometer is a new type of high-performance magnetometer. Since it can directly extract the Larmor precession frequency from the time-domain signal, there is no need for closed-loop frequency tracking. It is simpler and more reliable in hardware implementation and frequency extraction, and has better miniaturization potential. Since the pump light, radio frequency magnetic field and detection light are applied separately, the effects of photo-induced broadening and radio frequency broadening on the resonance linewidth are eliminated. During detection, the polarized atoms freely precess at the Larmor frequency without being affected by the pump light. Compared with the continuous pumping mode, the system optical frequency shift is suppressed, improving the accuracy of magnetic field measurement. The magnetometer structure of the free-precession vector atomic magnetometer can rely on traditional atomic magnetometers, but the effective coordination of excitation timing design and three-axis vector solution timing design, as well as the real-time display function, are difficult to achieve with existing instruments and equipment. Currently, there are many vector measurement methods based on atomic magnetometers, but the requirements for circuit design are very complex and real-time magnetic field measurement cannot be performed. Summary of the Invention

[0003] The purpose of the present invention is to provide an FPGA-based free precession vector atomic magnetometer excitation and measurement system, which can effectively excite the atomic magnetometer to generate a scalar free precession signal and a free precession signal under X, Y, and Z three-axis modulation, and according to the excitation timing, the four collected Larmor precession frequencies are vector-processed to display the magnitude and direction of the vector magnetic field amplitude in real time. The system has the advantages of good real-time performance, simple hardware structure, and convenient integration.

[0004] To achieve the above objectives, the present invention provides an FPGA-based free precession vector atomic magnetometer excitation measurement system, comprising a laser unit, an atomic magnetometer probe, a host computer, an optical pulse excitation unit, a magnetic pulse excitation unit, a three-axis vector magnetic modulation excitation unit, and a three-axis vector free precession signal acquisition and processing unit; the laser unit is connected to the atomic magnetometer probe and the optical pulse excitation unit, respectively; the three-axis vector magnetic modulation excitation unit is connected to the atomic magnetometer probe via a three-axis modulation coil, and the three-axis modulation coil is respectively installed in the X, Y, and Z directions of the atomic magnetometer probe; the magnetic pulse excitation unit is connected to the atomic magnetometer probe via an excitation coil, and the atomic magnetometer probe is connected to the three-axis vector free precession signal acquisition and processing unit; the three-axis magnetic modulation excitation unit, the magnetic pulse excitation unit, the optical pulse excitation unit, and the three-axis vector free precession signal acquisition and processing unit are interactively connected to the host computer via the FPGA.

[0005] Preferably, the laser unit includes a laser 1 and a laser 2, the laser 1 outputs detection light to the atomic magnetometer probe, and the laser 2 outputs pumping light, which is input to the atomic magnetometer probe through an AOM light intensity modulator.

[0006] Preferably, the magnetic pulse excitation unit includes an FPGA and a DAC1, and the FPGA controls the DAC1 to generate a magnetic pulse excitation signal to supply to the excitation coil.

[0007] Preferably, the optical pulse excitation unit includes an FPGA and a DAC2, and the FPGA controls the DAC2 to generate an optical pulse excitation signal to supply to the AOM optical intensity modulator.

[0008] Preferably, the three-axis vector magnetic modulation excitation unit includes FPGA, DAC3, DAC4 and DAC5, and the FPGA controls the DAC3, DAC4 and DAC5 to generate X-axis, Y-axis and Z-axis vector magnetic modulation signals, which are correspondingly transmitted to the X-axis, Y-axis and Z-axis modulation coils of the three-axis modulation coil. The DAC3 is connected to the Z-axis modulation coil, the DAC4 is connected to the X-axis modulation coil, and the DAC5 is connected to the Y-axis modulation coil.

[0009] Preferably, the three-axis vector free precession signal acquisition and processing unit includes an FPGA, a comparator and a transimpedance amplifier. The free precession signals of four different frequencies generated by the atomic magnetometer probe are first amplified by the transimpedance amplifier, and then shaped by the comparator and transmitted to the FPGA.

[0010] Preferably, the FPGA includes a three-axis vector magnetic field solution module and a high-precision multi-channel digital phase-shift frequency meter module. The high-precision multi-channel digital phase-shift frequency meter module extracts the Larmor precession frequency of the four free precession signals, and processes them in the three-axis vector magnetic field solution module to obtain three-axis vector magnetic field information.

[0011] Preferably, the host computer sends instructions to the FPGA, and the FPGA uploads three-axis vector magnetic field information to the host computer.

[0012] Preferably, the optical pulse excitation signal is a square wave signal with adjustable duty cycle, the magnetic excitation signal is a high-frequency sinusoidal wave signal, and the signal waveforms of the X-axis, Y-axis, and Z-axis vector magnetic modulation signals are square wave synchronous pulse signals.

[0013] Preferably, the high-precision multi-channel digital phase-shift frequency meter calls the PLL phase-locked loop inside the FPGA to convert the 50MHZ basic clock into a 1.5GHZ clock, thereby increasing the number of clocks to be measured.

[0014] Therefore, the present invention adopts the above-mentioned FPGA-based free precession vector atomic magnetometer excitation measurement system, which has the following beneficial effects:

[0015] (1) Compared with traditional excitation systems, the excitation system of the present invention effectively improves the bandwidth of the free precession atomic magnetometer. The measurement system uses FPGA to design a multi-channel phase-shifting frequency meter to improve the sensitivity index of the free precession optically pumped atomic magnetometer, and simplifies the circuit structure and reduces the circuit volume. The three-axis vector solution system designed based on FPGA fully utilizes the high-speed processing characteristics of FPGA to achieve the magnitude of the vector magnetic field solved once at the nanosecond level.

[0016] (2) The present invention can effectively stimulate atoms to generate free precession signals, designs a detection sequence, and realizes real-time measurement of the amplitude and direction of the three-axis vector magnetic field according to the detection sequence;

[0017] (3) Compared with the existing technology, the present invention has the advantages of good real-time performance, simple hardware structure, easy integration and low cost.

[0018] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 A schematic diagram of an FPGA-based free precession vector atomic magnetometer excitation and measurement system according to the present invention;

[0020] Figure 2 This is a three-axis vector excitation timing diagram of a free precession vector atomic magnetometer excitation measurement system based on FPGA of the present invention;

[0021] Figure 3 This is a three-axis vector measurement timing diagram of a FPGA-based free precession vector atomic magnetometer excitation measurement system of the present invention;

[0022] Figure 4 This is a working principle diagram of a high-precision multi-channel digital phase-shift frequency meter in an FPGA-based free-precession vector atomic magnetometer excitation measurement system according to the present invention. DETAILED DESCRIPTION

[0023] The following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but rather merely represents selected embodiments of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort shall fall within the scope of protection of the present invention.

[0024] Example

[0025] like Figure 1 As shown, the present invention provides an FPGA-based free precession vector atomic magnetometer excitation measurement system, comprising a laser unit, an atomic magnetometer probe, a host computer, an optical pulse excitation unit, a magnetic pulse excitation unit, a three-axis vector magnetic modulation excitation unit, and a three-axis vector free precession signal acquisition and processing unit. The laser unit is connected to the atomic magnetometer probe and the optical pulse excitation unit, respectively. The laser unit comprises a laser 1 and a laser 2. Laser 1 outputs detection light to the atomic magnetometer probe, and laser 2 outputs pumping light, which is modulated by an AOM optical intensity modulator and then input into the atomic magnetometer probe. The magnetic pulse excitation unit is connected to the atomic magnetometer probe via an excitation coil. The magnetic pulse excitation unit comprises an FPGA and a DAC1. The FPGA controls the DAC1 to generate a magnetic pulse excitation signal that is supplied to the excitation coil to form a pulse, thereby applying magnetic excitation to atoms and causing the atoms in the atomic magnetometer probe to enter a free precession state. The optical pulse excitation unit comprises an FPGA and a DAC2. The FPGA controls the DAC2 to generate an optical pulse excitation signal that is supplied to the AOM optical intensity modulator, thereby controlling the pumping light emitted by the laser 2 to apply optical excitation to the atoms.

[0026] The three-axis vector magnetic modulation excitation unit is connected to the atomic magnetometer probe through a three-axis modulation coil. The three-axis modulation coil is installed in the X, Y, and Z directions of the atomic magnetometer probe respectively; the atomic magnetometer probe is connected to the three-axis vector free precession signal acquisition and processing unit; the three-axis magnetic modulation excitation unit, magnetic pulse excitation unit, optical pulse excitation unit, and three-axis vector free precession signal acquisition and processing unit are interactively connected to the host computer through FPGA. The three-axis vector magnetic modulation excitation unit includes FPGA, DAC3, DAC4 and DAC5. FPGA controls DAC3, DAC4 and DAC5 to generate X-axis, Y-axis and Z-axis vector magnetic modulation signals, which are correspondingly transmitted to the X-axis, Y-axis and Z-axis modulation coils of the three-axis modulation coil. DAC3 is connected to the Z-axis modulation coil to apply a magnetic modulation signal in the Z-axis direction to the atoms so that the atoms in the atomic magnetometer probe enter a free precession state containing Z-axis vector information; DAC4 is connected to the X-axis modulation coil to apply a magnetic modulation signal in the X-axis direction to the atoms so that the atoms in the atomic magnetometer probe enter a free precession state containing X-axis vector information; DAC5 is connected to the Y-axis modulation coil to apply a magnetic modulation signal in the Y-axis direction to the atoms so that the atoms in the atomic magnetometer probe enter a free precession state containing Y-axis vector information; Figure 2 As shown, the magnetic modulation period is 4ms, and 1ms of magnetic excitation is applied in each process, causing the atoms to generate four different free precession signals to achieve three-axis vector solution.

[0027] For the free-precession vector atomic magnetometer, the difference between it and the traditional vector atomic magnetometer lies in the different application methods of light-excitation second pulses, magnetic excitation pulses and three-axis vector magnetic field modulation signals and the form of the final output signal. Take the simultaneous application of light and magnetic pulse excitation and the sequential application of three-axis vector magnetic modulation signals as an example.

[0028] A cycle can be divided into four parts: applying optical pulse excitation, RF magnetic field pulse excitation, three-axis vector magnetic modulation signal and signal detection. The first is the measurement method of the scalar field of the free precession atomic magnetometer, which is set to be carried out along the Z, Y, and X axes respectively. The magnetic field to be measured B0 is also along the Z axis. In the pumping phase, the atoms are polarized by the pump light, and the macroscopic magnetic moment M will be along the Z axis in the steady state. This process can be described by the Bloch equation:

[0029]

[0030] After the atoms are polarized to a steady state, M x =M y =0,M z =M0, then turn off the pump light, turn on the radio frequency magnetic field RF, and apply a radio frequency signal of 2B1cos (ω0t) along the Y axis. Since the action time of the radio frequency signal is very short, relaxation can be ignored. In this process, B1 and t2 need to be adjusted so that M zis 0, forming a π / 2 pulse to maximize the signal. This process is solved in the rotating coordinate system, and we can get:

[0031] M x = -M0sin(γB1t);

[0032] M y =0;

[0033] M z =M0cos(γB1t);

[0034] When the RF field is applied and reaches steady state, M y =M z =0,M x =M0, and use this as the initial value of the detection phase for solution. At this time, remove the RF pulse and enter the detection phase. Consider the relaxation term and return to the laboratory coordinate system, and we can get:

[0035]

[0036] M z =0;

[0037] Final M x or M y The expression of is the expression of the free precession signal.

[0038] Based on the scalar field measurement achieved by the free precession atomic magnetometer, three-axis vector measurement in the geomagnetic environment is achieved by sequentially applying three-axis vector magnetic modulation signals. The excitation timing design in the excitation system is based on the principle of the free precession vector atomic magnetometer. The excitation principle of this embodiment is as follows:

[0039] like Figure 3 As shown, the three-axis vector magnetic modulation signal can effectively extract the magnetic field vector information. First, solve x When obtaining the magnetic field information in the axial direction, according to the timing relationship of the three-axis vector magnetic modulation signal, when the x-axis magnetic modulation signal is in the rising edge stage, the measurement system stores ω0, and when the x-axis solution signal has a falling edge, it stores ω1. Finally, the magnetic field information of the x-axis is obtained by the three-axis vector free precession signal acquisition and processing unit. Secondly, when the y-axis solution signal has a falling edge, it stores ω2. Finally, the magnetic field information of the y-axis is obtained by the three-axis vector free precession signal acquisition and processing unit. Finally, when the z-axis solution signal has a falling edge, it stores ω3. Finally, the magnetic field information of the z-axis is obtained by the three-axis vector free precession signal acquisition and processing unit. Finally, this process is repeated periodically to obtain the three-axis vector magnetic field information.

[0040] When only RF magnetic field pulse excitation is applied without applying three-axis vector magnetic modulation signal, the magnetic field magnitude B0 is:

[0041]

[0042] At this time, the Larmor precession frequency ω0 collected from the free precession signal is:

[0043]

[0044] When the RF magnetic field pulse excitation and the X-axis magnetic modulation signal are applied simultaneously, B1 is:

[0045]

[0046] At this time, the Larmor precession frequency in the collected free precession signal is ω1;

[0047]

[0048] Combining the equations ω0 and ω1, we can get the magnitude of the magnetic field in the X direction as B. x ;

[0049]

[0050] Similarly, when applying RF magnetic field pulse excitation and Y-axis magnetic modulation signal at the same time, B can be calculated. y

[0051]

[0052] Similarly, when applying RF magnetic field pulse excitation and Z-axis magnetic modulation signal at the same time, B can be calculated. z

[0053]

[0054] The three-axis vector free precession signal acquisition and processing unit includes an FPGA, a comparator, and a transimpedance amplifier. After the excitation phase, the detection phase begins. Detection light from laser 1 enters the atomic magnetometer probe. Atoms in the gas chamber are sensitive to the detection light, generating four free precession signals of varying frequencies. After passing through the transimpedance amplifier, the comparator converts the free precession attenuation signal into a square wave before entering the FPGA. The FPGA includes a three-axis vector magnetic field solver module and a high-precision multi-channel digital phase-shift frequency counter module. The high-precision multi-channel digital phase-shift frequency counter module extracts the Larmor precession frequencies of the four free precession signals. The three-axis vector magnetic field solver module processes the signals to generate three-axis vector magnetic field information. The host computer issues instructions to the FPGA, which then uploads the three-axis vector magnetic field information to the host computer.

[0055] The optical pulse excitation signal is a square wave signal with adjustable duty cycle, the magnetic excitation signal is a high-frequency sine wave signal, and the signal waveforms of the X-axis, Y-axis, and Z-axis vector magnetic modulation signals are square wave synchronous pulse signals.

[0056] The excitation stage and the detection stage are divided into four times in total and are cycled periodically. The first is the detection stage after the excitation stage of the scalar field is completed. The detection light from laser 1 enters the atomic magnetometer probe, and the atoms in the gas chamber are sensitive to the detection light and generate an oscillating and attenuated free precession signal. The second is the detection stage after the excitation stage carrying the X-axis magnetic field information is completed. The detection light from laser 1 enters the atomic magnetometer probe, and the atoms in the gas chamber are sensitive to the detection light and generate an oscillating and attenuated free precession signal carrying the X-axis magnetic field information. The third is the detection stage after the excitation stage carrying the Y-axis magnetic field information is completed. The detection stage is entered. The detection light from laser 1 enters the atomic magnetometer probe, and the atoms in the gas chamber are sensitive to the detection light and generate an oscillating and attenuated free precession signal carrying the Y-axis magnetic field information. The fourth is the detection stage after the excitation stage carrying the Z-axis magnetic field information is completed. The detection light of laser 1 enters the atomic magnetometer probe. The atoms in the gas chamber are sensitive to the detection light and generate a free precession signal with oscillation and attenuation of Z-axis magnetic field information. Then, the free precession voltage signal is output through the transimpedance amplifier respectively. After preprocessing by the comparator module, a square wave signal of scalar field Larmor precession frequency information, a square wave signal carrying Larmor precession frequency information for solving the X-axis magnetic field direction, a square wave signal carrying Larmor precession frequency information for solving the Y-axis magnetic field direction, and a square wave signal carrying Larmor precession frequency information for solving the Z-axis magnetic field direction are obtained respectively. Finally, the signal enters the FPGA, and a gate is set inside the FPGA as the detection stage. The FPGA makes a unified timing distribution, and the end of each π / 2 pulse is used as the gate opening mark. The high-precision multi-channel digital phase-shift frequency meter calls the PLL phase-locked loop inside the FPGA to convert the 50MHZ base clock into a 1.5GHZ clock. Figure 4 As shown, the clock signal to be measured input by the high-precision comparator module is counted within the gate time to obtain cnt_c, and the high-frequency standard clock signal obtained by multiplying the FPGA system clock is counted to obtain cnt_l. For a known high-frequency standard clock signal frequency f s , then the clock frequency to be measured is f t It can be expressed as:

[0057]

[0058] The high-precision multi-channel digital phase-shift frequency meter based on FPGA design increases the number of clocks to be measured, improves the basic clock frequency, and thus improves the frequency measurement accuracy. Finally, four clock frequencies f to be measured are obtained. tThese are the scalar field Larmor precession frequency ω0, the X-axis magnetic field Larmor precession frequency ω1, the Y-axis magnetic field Larmor precession frequency ω2, and the Z-axis magnetic field Larmor precession frequency ω3. Finally, these four frequencies enter the FPGA's three-axis vector calculation module, where the four different frequencies are converted into three-axis vector magnetic field information based on the vector calculation principle. This information can be uploaded to a host computer for real-time display of the three-axis vector magnetic field information, and the exported data can be saved for subsequent processing and analysis. The host computer can also issue commands to the FPGA to interact with parameters such as the optical magnetic excitation signal and the three-axis vector magnetic modulation signal waveform, frequency, phase, and duty cycle. The FPGA also receives the three-axis vector magnetic field amplitude and magnitude uploaded by the FPGA for real-time display, and has the function of saving and exporting magnetic field amplitude data for subsequent processing and analysis.

[0059] Therefore, the present invention utilizes the aforementioned FPGA-based free-precession vector atomic magnetometer excitation and measurement system, effectively stimulating the atomic magnetometer to generate a scalar field free-precession signal and free-precession signals for the X, Y, and Z three-axis vector solution fields. Based on the timing requirements of the three-axis vector modulation signal, the system extracts four different Larmor free-precession frequencies in real time and then performs vector measurement-based solution, ultimately achieving real-time measurement of the three-axis vector magnetic field amplitude. Existing instruments and equipment struggle to meet the timing requirements of free-precession vector mode excitation, detection, and three-axis vector magnetic modulation due to inconsistent clocks. Currently, numerous atomic magnetometer-based vector measurement methods exist, but these methods require complex circuit design and are unable to perform real-time magnetic field measurements. The present invention offers advantages such as good real-time performance, simple hardware structure, ease of integration, low cost, and high bandwidth.

[0060] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the same. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solutions of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A free-precession vector atomic magnetometer excitation and measurement system based on FPGA, characterized by: The invention comprises a laser unit, an atomic magnetometer probe, a host computer, an optical pulse excitation unit, a magnetic pulse excitation unit, a three-axis vector magnetic modulation excitation unit and a three-axis vector free precession signal acquisition and processing unit; the laser unit is connected to the atomic magnetometer probe and the optical pulse excitation unit respectively; the three-axis vector magnetic modulation excitation unit is connected to the atomic magnetometer probe via a three-axis modulation coil, and the three-axis modulation coil is respectively installed in the X, Y and Z directions of the atomic magnetometer probe; the magnetic pulse excitation unit is connected to the atomic magnetometer probe via an excitation coil, and the atomic magnetometer probe is connected to the three-axis vector free precession signal acquisition and processing unit; the three-axis magnetic modulation excitation unit, the magnetic pulse excitation unit, the optical pulse excitation unit and the three-axis vector free precession signal acquisition and processing unit are interactively connected to the host computer via FPGA.

2. The FPGA-based free precession vector atomic magnetometer excitation measurement system according to claim 1, characterized in that: The laser unit includes a laser 1 and a laser 2. The laser 1 outputs detection light to the atomic magnetometer probe, and the laser 2 outputs pumping light, which is input to the atomic magnetometer probe through an AOM light intensity modulator.

3. The FPGA-based free precession vector atomic magnetometer excitation measurement system according to claim 1, characterized in that: The magnetic pulse excitation unit includes an FPGA and a DAC1. The FPGA controls the DAC1 to generate a magnetic pulse excitation signal to supply to the excitation coil.

4. The FPGA-based free precession vector atomic magnetometer excitation measurement system according to claim 1, characterized in that: The optical pulse excitation unit includes an FPGA and a DAC2. The FPGA controls the DAC2 to generate an optical pulse excitation signal to supply to the AOM optical intensity modulator.

5. The FPGA-based free precession vector atomic magnetometer excitation measurement system according to claim 1, characterized in that: The three-axis vector magnetic modulation excitation unit includes FPGA, DAC3, DAC4 and DAC5. The FPGA controls the DAC3, DAC4 and DAC5 to generate X-axis, Y-axis and Z-axis vector magnetic modulation signals, which are correspondingly transmitted to the X-axis, Y-axis and Z-axis modulation coils of the three-axis modulation coil. The DAC3 is connected to the Z-axis modulation coil, the DAC4 is connected to the X-axis modulation coil, and the DAC5 is connected to the Y-axis modulation coil.

6. The FPGA-based free precession vector atomic magnetometer excitation measurement system according to claim 1, characterized in that: The three-axis vector free precession signal acquisition and processing unit includes an FPGA, a comparator, and a transimpedance amplifier. The free precession signals of four different frequencies generated by the atomic magnetometer probe are first amplified by the transimpedance amplifier, then shaped by the comparator, and then transmitted to the FPGA.

7. The FPGA-based free precession vector atomic magnetometer excitation and measurement system according to claim 6, characterized in that: The FPGA includes a three-axis vector magnetic field solution module and a high-precision multi-channel digital phase-shift frequency meter module. The high-precision multi-channel digital phase-shift frequency meter module extracts the Larmor precession frequency of four free precession signals and processes them in the three-axis vector magnetic field solution module to obtain three-axis vector magnetic field information.

8. The FPGA-based free precession vector atomic magnetometer excitation and measurement system according to claim 1, characterized in that: The host computer sends instructions to the FPGA, and the FPGA uploads three-axis vector magnetic field information to the host computer.

9. The FPGA-based free precession vector atomic magnetometer excitation and measurement system according to claim 5, characterized in that: The optical pulse excitation signal is a square wave signal with adjustable duty cycle, the magnetic excitation signal is a high-frequency sine wave signal, and the signal waveforms of the X-axis, Y-axis, and Z-axis vector magnetic modulation signals are square wave synchronous pulse signals.

10. The FPGA-based free precession vector atomic magnetometer excitation and measurement system according to claim 7, characterized in that: The high-precision multi-channel digital phase-shift frequency meter calls the PLL phase-locked loop inside the FPGA to convert the 50MHZ basic clock into a 1.5GHZ clock, thereby increasing the number of clocks to be measured.

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