CN-121995723-A - CPT atomic clock control circuit and method for inhibiting magnetic field frequency shift

CN121995723ACN 121995723 ACN121995723 ACN 121995723ACN-121995723-A

Abstract

The invention discloses a CPT atomic clock control circuit for inhibiting magnetic field frequency shift, which comprises a main control chip, a demodulation circuit, a digital-to-analog conversion circuit, an analog-to-digital conversion circuit, a crystal oscillator, a voltage-controlled oscillator, a phase-locked loop circuit and a CPT atomic clock quantum system provided with a magnetic field coil. The invention also discloses a CPT atomic clock control method for inhibiting the magnetic field frequency shift, which measures the magnetic field of atomic feelings through a CPT principle and feeds back a compensation magnetic field to the atomic clock, thereby inhibiting the magnetic field frequency shift and improving the accuracy and stability of the output frequency of the atomic clock.

Inventors

LIU MENG
XUE XIAOBO
LIN ZAISHENG
WU CHENFEI
LV YUTAO
DING YUDONG
ZHANG SHENGKANG

Assignees

北京无线电计量测试研究所

Dates

Publication Date: 20260508
Application Date: 20251226

Claims (10)

1. The CPT atomic clock control circuit for inhibiting magnetic field frequency shift comprises a main control chip, a digital-to-analog conversion circuit, a microwave signal generation modulation unit, a CPT atomic clock quantum system provided with a magnetic field coil and an analog-to-digital conversion circuit, wherein the main control chip sends microwave generation signals to be received by the microwave signal generation modulation unit after being converted by the digital-to-analog conversion circuit, the main control chip also sends microwave control signals to the microwave signal generation modulation unit, the microwave signal generation modulation unit sends modulated microwave signals to the CPT atomic clock quantum system, the CPT atomic clock quantum system outputs microwave signal adjustment electric signals to be converted by the analog-to-digital conversion circuit and then enters the main control chip to complete closed loop locking of CPT atomic clock microwave frequency (signals), and the CPT atomic clock control circuit is characterized in that: The main control chip further comprises a magnetic field coil control module, wherein the magnetic field coil control module is used for inputting control voltage of a magnetic field coil to the CPT atomic clock quantum system to realize closed-loop locking of microwave signals related to a magnetic field and inhibit microwave frequency offset caused by magnetic field change.
2. The CPT atomic clock control circuit for suppressing a magnetic field frequency shift according to claim 1, wherein said CPT atomic clock quantum system comprises a laser, an atomic gas cell, a magnetic field coil, a heating element, a temperature measuring element, a photodetector; The atomic air chamber is used for receiving the laser and realizing CPT effect according to the interaction of the laser and atoms, and outputting an optical signal; the magnetic field coil is used for applying a magnetic field to the atomic air chamber and providing a laser and atomic interaction quantization axis; the heating element and the temperature measuring element are used for controlling the temperature of the atomic gas chamber; the photoelectric detector is used for receiving the optical signal, converting the optical signal into an electric signal and outputting the electric signal to the analog-to-digital conversion circuit.
3. The CPT atomic clock control circuit for suppressing magnetic field frequency shift according to claim 1 or 2, wherein the microwave signal generating and modulating unit comprises a crystal oscillator, a phase-locked loop circuit, and a voltage-controlled oscillator, the crystal oscillator receives the analog signal converted by the digital-to-analog conversion circuit, generates a frequency signal and sends the frequency signal to the phase-locked loop circuit, the phase-locked loop circuit receives the microwave control signal sent by the main control chip, modifies the amplification factor of the microwave frequency of the phase-locked loop circuit, and sends a control voltage to the voltage-controlled oscillator to regulate the output microwave frequency of the voltage-controlled oscillator, and the voltage-controlled oscillator finally generates a microwave signal related to the output frequency of the crystal oscillator.
4. The CPT atomic clock control circuit for suppressing magnetic field frequency shift according to claim 3, wherein the main control chip comprises a demodulation circuit, the demodulation circuit is used for demodulating a differential signal of a CPT resonance spectrum obtained by a CPT atomic clock quantum system, determining a zero point of a clock/magnetic sub-level transition CPT spectrum differential signal, and outputting a feedback signal to the crystal oscillator/magnetic field coil through the main control chip to lock the microwave frequency to the clock/magnetic sub-level transition frequency.
5. A CPT atomic clock control method for suppressing magnetic field frequency shift, based on a CPT atomic clock control circuit for suppressing magnetic field frequency shift according to any one of claims 1 to 4, comprising the steps of: Obtaining frequency amplification factors A1 and A2 of a phase-locked loop circuit corresponding to the clock transition frequency and the magnetic sub-level transition frequency of the CPT atomic clock quantum system; presetting the amplification factor of a phase-locked loop as A1, locking Zhong Yueqian microwave frequencies by scanning crystal oscillator control voltage, and recording a locked crystal oscillator control voltage value V and a locked loop accumulated error el; presetting a crystal oscillator control voltage value as V, modifying the amplification factor of a phase-locked loop as A2, modifying the control voltage of a magnetic field coil in the CPT atomic clock quantum system to enable a feedback error signal of a locking loop to be zero, and recording a magnetic field control voltage value B and a locking loop accumulated error e2 when the error is zero; the method comprises the steps of presetting a magnetic field control voltage value as B, modifying the amplification factor of a phase-locked loop as A1, reading a stored crystal oscillator control voltage locking loop accumulated error e1, outputting a new crystal oscillator control voltage value V and a new locking loop accumulated error e1 according to a demodulation result of a main control chip, and storing the new crystal oscillator control voltage value V and the new locking loop accumulated error e 1; the method comprises the steps of presetting a crystal oscillator control voltage value as V, modifying the amplification factor of a phase-locked loop as A2, reading a stored magnetic field control voltage locking loop accumulated error e2, outputting a new magnetic field control voltage value B and a new locking loop accumulated error e2 according to a demodulation result of a main control chip, and storing the new magnetic field control voltage value B and the new locking loop accumulated error e 2; And modifying the frequency amplification factor of the phase-locked loop circuit at a certain frequency, so that the amplification factors A1 and A2 alternately control microwave output, repeating the steps, and realizing the closed-loop locking of the clock transition signal and the closed-loop locking of the magnetic field signal through time division multiplexing.
6. The method for controlling a CPT atomic clock for suppressing a magnetic field frequency shift according to claim 5, wherein said obtaining frequency amplification factors A1 and A2 of a phase-locked loop circuit corresponding to a quantum system clock transition and a magnetic sub-level transition frequency of the CPT atomic clock specifically comprises: modifying the frequency amplification factor A1 of the phase-locked loop circuit through the main control chip, doubling the frequency output by the crystal oscillator to the required microwave frequency, and storing the value of A1; The method comprises the steps of presetting a crystal oscillator control voltage value as V, obtaining a differential signal of a CPT resonance spectrum through a demodulation circuit of a main control chip, determining a zero point of the CPT spectrum differential signal of the transition of a magneton energy level, determining a frequency amplification factor A2 of a phase-locked loop circuit corresponding to the zero point, and storing the frequency amplification factor A2.
7. The method for controlling a CPT atomic clock for suppressing magnetic field frequency shift according to claim 6, wherein the preset crystal oscillator control voltage value is V, the amplification factor of the phase-locked loop is modified to be A2, the stored accumulated error e2 of the magnetic field control voltage locked loop is read, and the new magnetic field control voltage value B and the new accumulated error e2 of the locked loop are output and stored according to the demodulation result of the main control chip, and the method specifically comprises: And determining the change of an external magnetic field signal by measuring the transition frequency of the magnetic sub-energy level of atoms in the CPT atomic clock, and modifying the internal magnetic field of the CPT atomic clock by adjusting the control voltage of the magnetic field coil, so that the differential signal of the CPT spectral line of the magnetic sub-energy level transition returns to the zero point again, thereby inhibiting the magnetic field frequency shift.
8. The method of claim 6, wherein the microwave frequency is one half of the transition frequency of the atomic ground state energy level Zhong Yue or the magnetic sub-level referenced by the CPT atomic clock.
9. An electronic device, comprising: at least one processor, at least one memory, and a communication interface, wherein, The processor, the memory and the communication interface are communicated with each other; The memory stores program instructions executable by the processor, the processor invoking the program instructions to perform the method of any of claims 5-8.
10. A non-transitory computer readable storage medium storing computer instructions that cause a computer to perform the method of any one of claims 5 to 8.

Description

CPT atomic clock control circuit and method for inhibiting magnetic field frequency shift Technical Field The invention relates to the technical field of atomic frequency standards, in particular to a CPT atomic clock control circuit and method for inhibiting magnetic field frequency shift. Background Coherent population trapping (Coherent population trapping, CPT) refers to the phenomenon that when atoms in a ground state pass through different channel transitions at the same time, mutual interference is generated between transition channels, so that the atoms are trapped in an overlapped state of the ground state, and no transition occurs. The coherent population trapping atomic clock utilizes the principle to obtain an error signal through the interaction of light and atoms so as to lock the crystal oscillator frequency. The CPT atomic clock mainly comprises a laser source, an atomic gas chamber, a heating element, a magnetic field coil, an optical element, a control circuit, a magnetic shielding part and the like. The atomic energy level will be shifted by the influence of the magnetic field and thus the atomic energy level transition frequency referenced by the CPT atomic clock will change, resulting in a change in the atomic clock output frequency. In general, a CPT atomic clock shields an external magnetic field using a magnetic shielding structure, but the shielding effect is often not ideal, and the atomic clock is still interfered by the external magnetic field in operation, so that the accuracy and stability of the output frequency of the atomic clock are deteriorated. Therefore, the invention provides a method and a circuit for inhibiting the magnetic field frequency shift of a CPT atomic clock, which utilize the CPT principle to measure the magnetic field size of atomic feelings and feed back a compensation magnetic field to the atomic clock, thereby inhibiting the magnetic field frequency shift and improving the accuracy and the stability of the output frequency of the atomic clock. Disclosure of Invention In view of the above, the present invention provides a CPT atomic clock control circuit and method for suppressing magnetic field frequency shift, which is implemented by measuring an external magnetic field of atoms, adjusting an internal magnetic field control voltage, changing the internal magnetic field to compensate for the change of the external magnetic field, and suppressing the magnetic field frequency shift. In order to achieve the above purpose, the invention adopts the following technical scheme: The invention provides a CPT atomic clock control circuit for inhibiting magnetic field frequency shift, which comprises a main control chip, a digital-to-analog conversion circuit, a microwave signal generation modulation unit, a CPT atomic clock quantum system provided with a magnetic field coil and an analog-to-digital conversion circuit, wherein the main control chip sends microwave generation signals, after being converted by the digital-to-analog conversion circuit, the microwave generation signals are received by the microwave signal generation modulation unit, the main control chip also sends microwave control signals to the microwave signal generation modulation unit, the microwave signal generation modulation unit sends modulated microwave signals to the CPT atomic clock quantum system, and the CPT atomic clock quantum system outputs microwave signal adjustment electric signals, after being converted by the analog-to-digital conversion circuit, the microwave signals enter the main control chip to complete closed-loop locking of microwave frequency (signal) of the CPT atomic clock, and is characterized in that: The main control chip further comprises a magnetic field coil control module, wherein the magnetic field coil control module is used for inputting control voltage of a magnetic field coil to the CPT atomic clock quantum system to realize closed-loop locking of microwave signals related to a magnetic field and inhibit microwave frequency offset caused by magnetic field change. In some possible embodiments, the CPT atomic clock quantum system includes a laser, an atomic gas cell, a magnetic field coil, a heating element, a temperature measuring element, a photodetector; The atomic air chamber is used for receiving the laser and realizing CPT effect according to the interaction of the laser and atoms, and outputting an optical signal; the magnetic field coil is used for applying a magnetic field to the atomic air chamber and providing a laser and atomic interaction quantization axis; the heating element and the temperature measuring element are used for controlling the temperature of the atomic gas chamber; the photoelectric detector is used for receiving the optical signal, converting the optical signal into an electric signal and outputting the electric signal to the analog-to-digital conversion circuit. In some possible embodiments, the microwave signal generating and mod