Calibration system and method of CPT atomic clock magnetic field coil constant

Abstract

The invention provides a CPT atomic clock magnetic field coil constant calibration system and method.The CPT atomic clock magnetic field coil constant calibration system comprises a CPT atomic clock, a frequency measurement module and an upper computer, the upper computer is used for setting the number of times of measurement, calculating a third analog signal in each time of measurement according to a first digital signal in each time of measurement, and sending the third analog signal to the CPT atomic clock; calculating the actual clock transition frequency during each measurement according to the frequency division number of the phase-locked loop circuit and the frequency of the clock signal during each measurement, calculating the external magnetic field during each measurement according to the actual clock transition frequency during each measurement, and finally performing linear fitting according to the external magnetic field during multiple measurements and the third analog signal to obtain a third analog signal; and obtaining a magnetic field coil constant. The invention provides a CPT atomic clock magnetic field coil constant calibration system and method. The system and method are used for solving the problems that a magnetic field coil in a CPT atomic clock is small and cannot be measured, current distribution calculation is complex due to the fact that magnetic shielding is applied, and the actual winding condition of the coil cannot be accurately simulated during simulation.

Description

Technical Field

[0001] The present invention relates to the field of quantum precision measurement, and in particular to a calibration system and method for a CPT atomic clock magnetic field coil constant. Background Art

[0002] In the field of quantum precision measurement, many measurement schemes and equipment require the use of magnetic field coils to apply magnetic fields, such as atomic magnetometers, atomic clocks, gyroscopes, etc. In atomic clocks, the transition frequency of the ground state Zeeman sublevel of atoms is used as a reference. The magnetic field provides a quantized axis for the interaction between light and atoms and separates the ground state magnetic sublevels of atoms, so it plays an important role. Therefore, it is very important to accurately control the size of the magnetic field, which can be achieved by calibrating the magnetic field coil constant.

[0003] There are currently two main methods for calibrating the magnetic field coil constant: direct measurement using a magnetometer and simulation calculation based on the current distribution of the coil. Although direct measurement using a magnetometer is simple and convenient, the magnetic field coil used in the miniaturized CPT atomic clock is too small to be inserted into the magnetometer for measurement. Since the CPT atomic clock applies magnetic shielding, the magnetic field generated by the coil will be distorted, so the calculation based on the current distribution is more complicated; at the same time, the actual winding condition of the coil cannot be accurately simulated during simulation. Summary of the invention

[0004] The present invention provides a calibration system and method for the magnetic field coil constant of a CPT atomic clock, so as to solve the problems that the magnetic field coil in the CPT atomic clock is too small to be measured, the current distribution calculation is relatively complicated due to the application of magnetic shielding, and the actual winding condition of the coil cannot be accurately simulated during simulation.

[0005] On the one hand, the present invention provides a calibration system for a CPT atomic clock magnetic field coil constant, comprising a CPT atomic clock, a frequency measurement module and a host computer, wherein the CPT atomic clock comprises a main control chip, a digital-to-analog conversion circuit, a physical system, an analog-to-digital conversion circuit, a crystal oscillator, a phase-locked loop circuit and a voltage-controlled oscillator, wherein:

[0006] The main control chip is used to output a first digital signal, and the size of the first digital signal is set by the host computer;

[0007] The digital-to-analog conversion circuit is used to convert the first digital signal into a first analog signal;

[0008] The physical system is used to output an electrical signal under the action of the first analog signal and the microwave signal, the first analog signal acts on the magnetic field coil in the physical system to generate a magnetic field, and the microwave signal is generated by the voltage-controlled oscillator;

[0009] The analog-to-digital conversion circuit is used to convert the electrical signal into a second digital signal;

[0010] The main control chip is used to obtain a third digital signal by performing negative feedback regulation on the second digital signal;

[0011] The digital-to-analog conversion circuit is used to convert the third digital signal into a second analog signal;

[0012] The crystal oscillator is used to generate a clock signal according to the second analog signal;

[0013] The phase-locked loop circuit is used to lock the frequency of the clock signal and the frequency of the microwave signal, and the frequency division number of the phase-locked loop circuit is set and read by the main control chip;

[0014] The frequency measurement module is used to measure the frequency of the clock signal;

[0015] The host computer is used to set the number of measurements, calculate the size of the first analog signal in each measurement according to the size of the first digital signal in each measurement, calculate the actual clock transition frequency in each measurement according to the frequency division number of the phase-locked loop circuit and the frequency of the clock signal measured each time, and calculate the external magnetic field in each measurement according to the actual clock transition frequency in each measurement, and finally perform linear fitting according to the external magnetic field and the size of the first analog signal during multiple measurements to obtain the magnetic field coil constant.

[0016] Optionally, the physical system includes a laser, an atomic gas chamber, the magnetic field coil and a photodetector, wherein:

[0017] The laser is used to emit laser light under the action of the microwave signal;

[0018] The atomic gas chamber is used to realize the CPT effect between atoms and the laser under the action of the magnetic field and output an optical signal;

[0019] The magnetic field coil is used to apply the magnetic field to the atomic gas chamber under the action of the first analog signal;

[0020] The photodetector is used to convert the optical signal into the electrical signal.

[0021] Optionally, the physical system further includes a heating element and a temperature measuring element, and the heating element and the temperature measuring element are used to control the temperature of the atomic gas chamber.

[0022] Optionally, the calculating the actual clock transition frequency in each measurement according to the frequency division number of the phase-locked loop circuit and the frequency of the clock signal measured each time includes:

[0023] The actual clock transition frequency at each measurement is calculated according to the following formula:

[0024]

[0025] Among them, f i is the actual clock transition frequency at the time of the ith measurement, N is the integer part of the frequency division number of the microwave signal, FN is the numerator of the fractional part of the frequency division number of the microwave signal, FD is the denominator of the fractional part of the frequency division number of the microwave signal, and f XO，i is the frequency of the clock signal measured for the i-th time, R is the frequency division number of the clock signal, and N, FN, FD and R constitute the frequency division number of the phase-locked loop circuit.

[0026] Optionally, calculating the external magnetic field at each measurement according to the actual clock transition frequency at each measurement includes:

[0027] The external magnetic field during each measurement is calculated according to the following formula:

[0028] f i =f0+K0B i 2

[0029] Where f0 is the ideal clock transition frequency, K0 is the coefficient related to the alkali metal atoms used in the CPT atomic clock, and B i is the external magnetic field during the i-th measurement.

[0030] Optionally, performing linear fitting according to the magnitude of the external magnetic field and the first analog signal during multiple measurements to obtain the magnetic field coil constant includes:

[0031] The linear fitting is performed according to the following formula to obtain the magnetic field coil constant:

[0032] B i =aV i +b

[0033] Among them, V i is the magnitude of the first analog signal during the i-th measurement, a is the magnetic field coil constant, and b is other influencing factors.

[0034] On the other hand, the present invention provides a method for calibrating the magnetic field coil constant of a CPT atomic clock, which is applied to any of the above systems and is characterized by comprising:

[0035] Use the host computer to set the number of measurements;

[0036] Using the host computer to calculate the size of the first analog signal at each measurement according to the size of the first digital signal at each measurement;

[0037] The host computer is used to calculate the actual clock transition frequency at each measurement according to the frequency division number of the phase-locked loop circuit and the frequency of the clock signal measured each time, wherein the frequency division number of the phase-locked loop circuit is obtained by the host computer from the main control chip at any measurement, and the frequency of the clock signal measured each time is obtained by the host computer from the frequency measurement module when the CPT atomic clock operates normally;

[0038] Using the host computer to calculate the external magnetic field at each measurement according to the actual clock transition frequency at each measurement;

[0039] The host computer is used to perform linear fitting according to the magnitude of the external magnetic field and the first analog signal during multiple measurements to obtain the magnetic field coil constant.

[0040] Optionally, the using the host computer to calculate the actual clock transition frequency in each measurement according to the frequency division number of the phase-locked loop circuit and the frequency of the clock signal measured each time includes:

[0041] The host computer is used to calculate the actual clock transition frequency during each measurement according to the following formula:

[0042]

[0043] Among them, f i is the actual clock transition frequency at the time of the ith measurement, N is the integer part of the frequency division number of the microwave signal, FN is the numerator of the decimal part of the frequency division number of the microwave signal, FD is the denominator of the decimal part of the frequency division number of the microwave signal, and f XO，i is the frequency of the clock signal measured for the i-th time, R is the frequency division number of the clock signal, and N, FN, FD and R constitute the frequency division number of the phase-locked loop circuit.

[0044] Optionally, the using the host computer to calculate the external magnetic field at each measurement according to the actual clock transition frequency at each measurement includes:

[0045] The host computer is used to calculate the external magnetic field during each measurement according to the following formula:

[0046] f i =f0+K0B i 2

[0047] Where f0 is the ideal clock transition frequency, K0 is the coefficient related to the alkali metal atoms used in the CPT atomic clock, and B i is the external magnetic field during the i-th measurement.

[0048] Optionally, the use of the host computer to perform linear fitting according to the magnitude of the external magnetic field and the first analog signal during multiple measurements to obtain the magnetic field coil constant includes:

[0049] The host computer is used to perform the linear fitting according to the following formula to obtain the magnetic field coil constant:

[0050] B i =aV i +b

[0051] Among them, V i is the magnitude of the first analog signal during the i-th measurement, a is the magnetic field coil constant, and b is other influencing factors.

[0052] The present invention proposes to in-situ calibrate the magnetic field coil constant of a CPT atomic clock based on the principle of the CPT atomic clock itself, and to reversely infer the magnetic field through the change in the output frequency of the atomic clock caused by the magnetic field, so as to obtain the coil constant in the CPT atomic clock. The scheme is reasonable and easy to operate, and effectively solves the problems that the magnetic field coil in the CPT atomic clock is too small to be measured, the current distribution calculation is relatively complicated due to the application of magnetic shielding, and the actual winding condition of the coil cannot be accurately simulated during simulation. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0054] Figure 1 A schematic diagram of a framework of a calibration system for a CPT atomic clock magnetic field coil constant provided in an embodiment of the present invention;

[0055] Figure 2 A schematic flow chart of a method for calibrating a CPT atomic clock magnetic field coil constant provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0056] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0057] Figure 1 The framework of a calibration system for the magnetic field coil constant of a CPT atomic clock provided by an embodiment of the present invention is shown in detail, including a CPT atomic clock, a frequency measurement module and a host computer. The CPT atomic clock includes a main control chip, a digital-to-analog conversion circuit, a physical system, an analog-to-digital conversion circuit, a crystal oscillator, a phase-locked loop circuit and a voltage-controlled oscillator.

[0058] The main control chip is used to output a first digital signal, and the size of the first digital signal is set by the host computer.

[0059] The digital-to-analog conversion circuit is used for converting the first digital signal into a first analog signal.

[0060] The physical system is used to output an electrical signal under the action of a first analog signal and a microwave signal. The first analog signal acts on a magnetic field coil in the physical system to generate a magnetic field, and the microwave signal is generated by a voltage-controlled oscillator.

[0061] In one example, a physical system includes a laser, an atomic gas cell, a magnetic field coil, and a photodetector, wherein:

[0062] The laser is used to emit laser light under the action of microwave signals;

[0063] The atomic gas chamber is used to realize the CPT effect between atoms and lasers under the action of a magnetic field and output optical signals;

[0064] The magnetic field coil is used to apply a magnetic field to the atomic gas chamber under the action of a first analog signal;

[0065] The photodetector is used to convert the optical signal into an electrical signal, which is the error between the atomic energy level transition frequency and the microwave signal frequency.

[0066] The microwave signal is loaded onto the control current of the laser to control the laser output.

[0067] Furthermore, the physical system also includes a heating element and a temperature measuring element, and the heating element and the temperature measuring element are used to control the temperature of the atomic gas chamber.

[0068] The analog-to-digital conversion circuit is used to convert the electrical signal into a second digital signal.

[0069] The main control chip is used to obtain a third digital signal by performing negative feedback regulation on the second digital signal. Negative feedback regulation can be achieved through algorithms such as PID control.

[0070] The digital-to-analog conversion circuit is used for converting the third digital signal into a second analog signal.

[0071] The crystal oscillator is used to generate a clock signal according to the second analog signal.

[0072] The phase-locked loop circuit is used to lock the frequency of the clock signal and the frequency of the microwave signal. The frequency division number of the phase-locked loop circuit is set and read by the main control chip.

[0073] The phase-locked loop circuit locks the frequency of the clock signal and the frequency of the microwave signal through the frequency division number.

[0074] In one example, the main control chip sets and reads the frequency division number of the phase-locked loop circuit through serial port communication.

[0075] The CPT atomic clock multiplies the clock signal generated by a crystal oscillator into a microwave signal through a phase-locked loop circuit, then compares the error between the microwave signal frequency and the atomic energy level transition frequency, and feeds this error back as a voltage control signal of the crystal oscillator through the main control chip to achieve locking of the clock signal frequency.

[0076] The frequency measurement module is used to measure the frequency of the clock signal.

[0077] The host computer is used to set the number of measurements, calculate the size of the first analog signal in each measurement according to the size of the first digital signal in each measurement, calculate the actual clock transition frequency in each measurement according to the frequency division number of the phase-locked loop circuit and the frequency of the clock signal in each measurement, and calculate the external magnetic field in each measurement according to the actual clock transition frequency in each measurement. Finally, linear fitting is performed based on the external magnetic field and the size of the first analog signal during multiple measurements to obtain the magnetic field coil constant.

[0078] Typically, the host computer calculates the size of the first analog signal based on the size of the first digital signal in combination with a reference voltage of the digital-to-analog conversion chip and the number of bits of the chip.

[0079] In one example, calculating the actual clock transition frequency in each measurement according to the frequency division number of the phase-locked loop circuit and the frequency of the clock signal measured each time includes:

[0080] The actual clock transition frequency at each measurement is calculated according to the following formula:

[0081]

[0082] Among them, f i is the actual clock transition frequency at the time of the ith measurement, N is the integer part of the frequency division number of the microwave signal, FN is the numerator of the decimal part of the frequency division number of the microwave signal, FD is the denominator of the decimal part of the frequency division number of the microwave signal, and f XO，i is the frequency of the clock signal measured for the i-th time, R is the frequency division factor of the clock signal, and N, FN, FD and R constitute the frequency division factor of the phase-locked loop circuit.

[0083] Further, calculating the external magnetic field at each measurement according to the actual clock transition frequency at each measurement includes:

[0084] The external magnetic field at each measurement is calculated according to the following formula:

[0085] f i =f0+K0B i 2

[0086] Where f0 is the ideal clock transition frequency, K0 is the coefficient related to the alkali metal atoms used in the CPT atomic clock. For example, when the alkali metal atoms are 87 When Rb, K0=5.73×10 10 Hz / T 2 , B i is the external magnetic field during the i-th measurement.

[0087] Furthermore, a linear fit is performed based on the magnitude of the external magnetic field and the first analog signal during multiple measurements to obtain the magnetic field coil constants including:

[0088] Perform linear fitting according to the following formula to obtain the magnetic field coil constant:

[0089] B i =aV i +b

[0090] Among them, V i is the magnitude of the first analog signal during the i-th measurement, a is the magnetic field coil constant, and b is other influencing factors, including the residual magnetism in the CPT atomic clock and other influencing factors.

[0091] Based on the same inventive concept, Figure 2 The flow chart of a method for calibrating a magnetic field coil constant of a CPT atomic clock provided by an embodiment of the present invention is shown, and is applied to the above-mentioned system, including:

[0092] Use the host computer to set the number of measurements;

[0093] Using a host computer to calculate the size of the first analog signal at each measurement according to the size of the first digital signal at each measurement;

[0094] The host computer is used to calculate the actual clock transition frequency at each measurement based on the frequency division number of the phase-locked loop circuit and the frequency of the clock signal measured each time. The frequency division number of the phase-locked loop circuit is obtained by the host computer from the main control chip at any measurement, and the frequency of the clock signal measured each time is obtained by the host computer from the frequency measurement module when the CPT atomic clock is operating normally;

[0095] Use the host computer to calculate the external magnetic field at each measurement based on the actual clock transition frequency at each measurement;

[0096] A host computer is used to perform linear fitting according to the magnitude of the external magnetic field and the first analog signal during multiple measurements to obtain the magnetic field coil constant.

[0097] A pin in the main control chip of the CPT atomic clock is used as the lock indication level. When the CPT atomic clock is locked and running normally, the indication level will change.

[0098] In one example, using a host computer to calculate the actual clock transition frequency in each measurement according to the frequency division number of the phase-locked loop circuit and the frequency of the clock signal measured each time includes:

[0099] Use the host computer to calculate the actual clock transition frequency for each measurement according to the following formula:

[0100]

[0101] Among them, f i is the actual clock transition frequency at the time of the ith measurement, N is the integer part of the frequency division number of the microwave signal, FN is the numerator of the decimal part of the frequency division number of the microwave signal, FD is the denominator of the decimal part of the frequency division number of the microwave signal, and f XO，i is the frequency of the clock signal measured for the i-th time, R is the frequency division factor of the clock signal, and N, FN, FD and R constitute the frequency division factor of the phase-locked loop circuit.

[0102] Further, using the host computer to calculate the external magnetic field at each measurement according to the actual clock transition frequency at each measurement includes:

[0103] Use the host computer to calculate the external magnetic field at each measurement according to the following formula:

[0104] f i =f0+K0B i 2

[0105] Where f0 is the ideal clock transition frequency, K0 is the coefficient related to the alkali metal atoms used in the CPT atomic clock, and B i is the external magnetic field during the i-th measurement.

[0106] Furthermore, the host computer is used to perform linear fitting according to the magnitude of the external magnetic field and the first analog signal during multiple measurements, and the magnetic field coil constants are obtained, including:

[0107] Use the host computer to perform linear fitting according to the following formula to obtain the magnetic field coil constant:

[0108] B i =aV i +b

[0109] Among them, V i is the magnitude of the first analog signal during the i-th measurement, a is the magnetic field coil constant, and b is other influencing factors.

[0110] Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0111] Obviously, those skilled in the art can make various changes and modifications to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is also intended to include these modifications and variations.

Claims

1. A calibration system for the magnetic field coil constant of a CPT atomic clock, characterized in that: It includes a CPT atomic clock, a frequency measurement module and a host computer. The CPT atomic clock includes a main control chip, a digital-to-analog conversion circuit, a physical system, an analog-to-digital conversion circuit, a crystal oscillator, a phase-locked loop circuit and a voltage-controlled oscillator, among which: The main control chip is used to output a first digital signal, and the size of the first digital signal is set by the host computer; The digital-to-analog conversion circuit is used to convert the first digital signal into a first analog signal; The physical system is used to output an electrical signal under the action of the first analog signal and the microwave signal, the first analog signal acts on the magnetic field coil in the physical system to generate a magnetic field, and the microwave signal is generated by the voltage-controlled oscillator; The analog-to-digital conversion circuit is used to convert the electrical signal into a second digital signal; The main control chip is used to obtain a third digital signal by performing negative feedback regulation on the second digital signal; The digital-to-analog conversion circuit is used to convert the third digital signal into a second analog signal; The crystal oscillator is used to generate a clock signal according to the second analog signal; The phase-locked loop circuit is used to lock the frequency of the clock signal and the frequency of the microwave signal, and the frequency division number of the phase-locked loop circuit is set and read by the main control chip; The frequency measurement module is used to measure the frequency of the clock signal; The host computer is used to set the number of measurements, calculate the size of the first analog signal in each measurement according to the size of the first digital signal in each measurement, calculate the actual clock transition frequency in each measurement according to the frequency division number of the phase-locked loop circuit and the frequency of the clock signal measured each time, and calculate the external magnetic field in each measurement according to the actual clock transition frequency in each measurement, and finally perform linear fitting according to the external magnetic field and the size of the first analog signal during multiple measurements to obtain the magnetic field coil constant.

2. The system according to claim 1, characterized in that: The physical system comprises a laser, an atomic gas chamber, the magnetic field coil and a photodetector, wherein: The laser is used to emit laser light under the action of the microwave signal; The atomic gas chamber is used to realize the CPT effect between atoms and the laser under the action of the magnetic field and output an optical signal; The magnetic field coil is used to apply the magnetic field to the atomic gas chamber under the action of the first analog signal; The photodetector is used to convert the optical signal into the electrical signal.

3. The system according to claim 2, characterized in that: The physical system also includes a heating element and a temperature measuring element, and the heating element and the temperature measuring element are used to control the temperature of the atomic gas chamber.

4. The system according to claim 1, characterized in that: The step of calculating the actual clock transition frequency in each measurement according to the frequency division number of the phase-locked loop circuit and the frequency of the clock signal measured each time comprises: The actual clock transition frequency at each measurement is calculated according to the following formula: Among them, f i is the actual clock transition frequency at the time of the ith measurement, N is the integer part of the frequency division number of the microwave signal, FN is the numerator of the fractional part of the frequency division number of the microwave signal, FD is the denominator of the fractional part of the frequency division number of the microwave signal, and f XO,i is the frequency of the clock signal measured for the i-th time, R is the frequency division number of the clock signal, and N, FN, FD and R constitute the frequency division number of the phase-locked loop circuit.

5. The system according to claim 4, characterized in that: Calculating the external magnetic field at each measurement according to the actual clock transition frequency at each measurement comprises: The external magnetic field during each measurement is calculated according to the following formula: f i =f0+K0B i 2 Where f0 is the ideal clock transition frequency, K0 is the coefficient related to the alkali metal atoms used in the CPT atomic clock, and B i is the external magnetic field during the i-th measurement.

6. The system according to claim 5, characterized in that: The linear fitting is performed according to the magnitude of the external magnetic field and the first analog signal during multiple measurements to obtain the magnetic field coil constant, which includes: The linear fitting is performed according to the following formula to obtain the magnetic field coil constant: B i =aV i +b Among them, V i is the magnitude of the first analog signal during the i-th measurement, a is the magnetic field coil constant, and b is other influencing factors.

7. A method for calibrating the magnetic field coil constant of a CPT atomic clock, applied to the system described in any one of claims 1 to 6, characterized in that: include: Use the host computer to set the number of measurements; Using the host computer to calculate the size of the first analog signal at each measurement according to the size of the first digital signal at each measurement; The host computer is used to calculate the actual clock transition frequency at each measurement according to the frequency division number of the phase-locked loop circuit and the frequency of the clock signal measured each time, wherein the frequency division number of the phase-locked loop circuit is obtained by the host computer from the main control chip at any measurement, and the frequency of the clock signal measured each time is obtained by the host computer from the frequency measurement module when the CPT atomic clock operates normally; Using the host computer to calculate the external magnetic field at each measurement according to the actual clock transition frequency at each measurement; The host computer is used to perform linear fitting according to the magnitude of the external magnetic field and the first analog signal during multiple measurements to obtain the magnetic field coil constant.

8. The method according to claim 7, characterized in that: The method of using the host computer to calculate the actual clock transition frequency in each measurement according to the frequency division number of the phase-locked loop circuit and the frequency of the clock signal measured each time comprises: The host computer is used to calculate the actual clock transition frequency during each measurement according to the following formula: Among them, f i is the actual clock transition frequency at the time of the ith measurement, N is the integer part of the frequency division number of the microwave signal, FN is the numerator of the fractional part of the frequency division number of the microwave signal, FD is the denominator of the fractional part of the frequency division number of the microwave signal, and f XO,i is the frequency of the clock signal measured for the i-th time, R is the frequency division number of the clock signal, and N, FN, FD and R constitute the frequency division number of the phase-locked loop circuit.

9. The method according to claim 8, characterized in that: The using the host computer to calculate the external magnetic field at each measurement according to the actual clock transition frequency at each measurement comprises: The host computer is used to calculate the external magnetic field during each measurement according to the following formula: f i =f0+K0B i 2 Where f0 is the ideal clock transition frequency, K0 is the coefficient related to the alkali metal atoms used in the CPT atomic clock, and B i is the external magnetic field during the i-th measurement.

10. The method according to claim 9, characterized in that: The use of the host computer to perform linear fitting according to the magnitude of the external magnetic field and the first analog signal during multiple measurements to obtain the magnetic field coil constant includes: The host computer is used to perform the linear fitting according to the following formula to obtain the magnetic field coil constant: B i =aV i +b Among them, V i is the magnitude of the first analog signal during the i-th measurement, a is the magnetic field coil constant, and b is other influencing factors.

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