CPT atomic clock microwave modulation method and device based on discrete sine wave frequency modulation

Abstract

The invention discloses a CPT atomic clock microwave modulation method and device based on discrete sine wave frequency modulation. The method comprises the following steps: determining a frequency discrimination signal frequency; determining a charge pump current value according to the frequency discrimination signal frequency; according to the charge pump current value, determining a center frequency by setting a numerator frequency division coefficient and a denominator frequency division coefficient and combining the frequency discrimination signal frequency; determining a VCO frequency band and a tuning range according to the center frequency; determining a target bandwidth and a phase margin according to the VCO frequency band and the tuning range, designing a third-order passive loop filter, and filtering a VCO output signal to obtain a filtered carrier signal; and according to the carrier signal, determining a modulation frequency, determining a maximum frequency offset, determining a frequency offset value and adjusting a microwave power gain so as to generate a frequency modulated signal. According to the method, the spectrum broadening of the modulated microwave signal can be reduced, and the short-term frequency stability of the CPT atomic clock is improved.

Description

Technical Field

[0001] The present application relates to the field of time and frequency precision measurement, and in particular to a CPT atomic clock microwave modulation method and device based on discrete sine wave frequency modulation. Background Art

[0002] The coherent population trapped (CPT) atomic clock is a precision time and frequency measurement device based on the coherent population trapping effect. Compared with traditional atomic clocks, CPT atomic clocks do not require a microwave resonant cavity, so their size and power consumption are greatly reduced while maintaining high-precision performance. They have broad application prospects and market value in autonomous navigation, time and frequency standards, micro-nano satellites, and unmanned driving.

[0003] From the working principle of the CPT atomic clock, we know that the optical frequency shift caused by the Stark Effect is one of the important factors affecting the frequency stability of the atomic clock, which involves the influence of various optical frequency components on the energy levels of alkali metal atoms. Although the microwave signal does not directly act on the atoms, when comprehensively considering the effects of various sidebands, it is necessary to consider the influence of the sideband expansion caused by microwave frequency modulation on the coherent two-color light.

[0004] At present, the microwave signal in the CPT atomic clock mainly adopts the 2FSK modulation method based on the phase-locked loop (PLL). The frequency hopping is achieved by adjusting the frequency division factor of the phase-locked loop. It has the advantages of precise frequency switching and simple implementation. However, this method has the following shortcomings in practical applications: (1) Frequency hopping will cause the spectrum of the microwave signal to be broadened, which increases the spectral components involved in the atomic transition, reduces the coherence between the microwave signal and the atomic transition, and thus affects the frequency stability; (2) During the modulation process, the center frequency of the microwave signal may shift. This shift will interfere with the matching of the microwave signal with the atomic resonance frequency and affect the locking accuracy of the CPT signal; (3) Due to the slow frequency switching speed of the PLL, when the microwave signal needs to be adjusted quickly, the dynamic response capability of the 2FSK modulation may be insufficient, affecting the real-time performance of the system. Contents of the invention Aiming at the shortcomings of the existing microwave modulation method of CPT atomic clock, the present invention proposes a microwave modulation method and device based on discrete sine wave frequency modulation. By adopting direct digital frequency synthesis (DDS) technology, using a single-chip microcomputer to accurately program and control the digital phase-locked loop chip, calling the discrete FSK function inside the phase-locked loop chip, realizing continuous switching of multiple carrier frequencies, and combining the physical system and circuit system to realize the sinusoidal modulation of the microwave frequency of the CPT atomic clock.

[0005] According to a first aspect of an embodiment of the present application, a CPT atomic clock microwave modulation method based on discrete sine wave frequency modulation is provided, comprising: Obtain the input frequency, doubler, pre-R divider, doubler and R divider of the phase-locked loop chip to determine the frequency of the demodulation signal; Determining a charge pump current value according to the frequency of the frequency discrimination signal; According to the charge pump current value, by setting the numerator frequency division coefficient and the denominator frequency division coefficient, combined with the frequency discrimination signal frequency, the center frequency is determined; Determine the VCO frequency band and tuning range according to the center frequency; According to the VCO frequency band and tuning range, a target bandwidth and phase margin are determined, a third-order passive loop filter is designed, and the VCO output signal is filtered to obtain a filtered carrier signal; According to the carrier signal, the modulation frequency, the maximum frequency deviation, the frequency deviation value and the microwave power gain are determined, thereby generating a frequency modulation signal.

[0006] According to a second aspect of an embodiment of the present application, a CPT atomic clock microwave modulation device based on discrete sine wave frequency modulation is provided, characterized in that it includes: The first determination module is used to obtain the input frequency of the phase-locked loop chip, the doubler, the pre-R divider, the multiplier and the R divider to determine the frequency of the frequency discrimination signal; A second determination module, used to determine a charge pump current value according to the frequency of the frequency discrimination signal; A third determination module is used to determine the center frequency according to the charge pump current value by setting the numerator frequency division coefficient and the denominator frequency division coefficient in combination with the frequency of the frequency discrimination signal; A fourth determination module, used to determine a VCO frequency band and a tuning range according to the center frequency; A fifth determination module is used to determine the target bandwidth and phase margin according to the VCO frequency band and tuning range, design a third-order passive loop filter, filter the VCO output signal, and obtain a filtered carrier signal; The generating module is used to determine the modulation frequency, the maximum frequency deviation, the frequency deviation value and adjust the microwave power gain according to the carrier signal, so as to generate a frequency modulation signal.

[0007] According to a second aspect of an embodiment of the present application, there is provided an electronic device, including: one or more processors; A memory for storing one or more programs; When the one or more programs are executed by the one or more processors, the one or more processors implement the method as described in the first aspect.

[0008] According to a second aspect of an embodiment of the present application, a computer-readable storage medium is provided, on which computer instructions are stored. When the instructions are executed by a processor, the steps of the method described in the first aspect are implemented.

[0009] The technical solution provided by the embodiments of the present application may have the following beneficial effects: It can be seen from the above embodiments that the present application adopts direct digital frequency synthesis technology, combined with the discrete FSK function of the digital phase-locked loop chip, to achieve continuous switching of multiple carrier frequencies. Compared with the existing frequency modulation schemes based on analog circuits (such as sine wave modulation and triangle wave modulation), this scheme overcomes the problems of difficult debugging, complex implementation and large frequency deviation, and significantly improves the short-term frequency stability of the CPT atomic clock. At the same time, without increasing the complexity of the hardware, the scheme can flexibly adjust the modulation depth and frequency using a microprocessor, further improving the performance of the microwave modulated signal. In addition, the scheme can effectively improve the signal-to-noise ratio of the demodulation signal under a specific modulation index, optimize the narrowband frequency modulation signal, greatly compress the CPT signal line width, and enhance the reliability and stability of the system.

[0010] It should be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0012] Figure 1 is a diagram showing the overall structure of a CPT atomic clock according to an exemplary embodiment.

[0013] Figure 2 The present invention is a flow chart of a CPT atomic clock microwave modulation method based on discrete sine wave frequency modulation according to an exemplary embodiment.

[0014] Figure 3 is a diagram showing the relationship between modulation frequency and frequency deviation according to an exemplary embodiment.

[0015] Figure 4 It is a block diagram of a CPT atomic clock microwave modulation device based on discrete sine wave frequency modulation according to an exemplary embodiment. DETAILED DESCRIPTION

[0016] Exemplary embodiments will be described in detail herein, examples of which are shown in the accompanying drawings. When the following description refers to the drawings, the same numbers in different drawings represent the same or similar elements unless otherwise indicated. The implementations described in the following exemplary embodiments do not represent all implementations consistent with the present application. Instead, they are merely examples of devices and methods consistent with some aspects of the present application as detailed in the appended claims.

[0017] The terms used in this application are for the purpose of describing specific embodiments only and are not intended to limit this application. The singular forms of "a", "said" and "the" used in this application and the appended claims are also intended to include plural forms unless the context clearly indicates other meanings. It should also be understood that the term "and / or" used herein refers to and includes any or all possible combinations of one or more associated listed items.

[0018] It should be understood that although the terms first, second, third, etc. may be used in the present application to describe various information, these information should not be limited to these terms. These terms are only used to distinguish the same type of information from each other. For example, without departing from the scope of the present application, the first information may also be referred to as the second information, and similarly, the second information may also be referred to as the first information. Depending on the context, the word "if" as used herein may be interpreted as "at the time of" or "when" or "in response to determining".

[0019] like Figure 1 As shown in the figure, the structure of the CPT atomic clock consists of a physical system and a circuit system. The physical system includes: a laser, a quarter wave plate, an atomic gas chamber, and a magnetically shielded shell; the circuit system includes: a photodetector (PD), a bandpass filter, a microprocessor, a voltage-controlled constant current source, a crystal oscillator, a radio frequency generator, a power amplifier, and a Bias-Tee. The microprocessor, the radio frequency generator, and the power amplifier together constitute the microwave modulation unit of the CPT atomic clock. The radio frequency generator generates a stable microwave signal through its internal charge pump phase-locked loop, and its main components include: a phase frequency detector (PFD), a loop filter, a voltage-controlled oscillator (VCO), an integer N divider, and a delta-sigma modulator. The microprocessor can control the frequency of the microwave signal output by the radio frequency generator, and the power amplifier can adjust the power of the microwave signal output by the radio frequency generator.

[0020] Figure 2 is a flow chart of a CPT atomic clock microwave modulation method based on discrete sine wave frequency modulation according to an exemplary embodiment. Figure 2 As shown, the method is applied in a terminal and may include the following steps: S1: Obtain the input frequency of the phase-locked loop chip, the doubler, the pre-R divider, the doubler and the R divider to determine the frequency of the demodulation signal; Specifically, obtain the input frequency of the phase-locked loop chip , the frequency multiplication factor OSC_2X of the doubler, the frequency division factor PLL_R_PRE of the pre-R divider, the frequency multiplication factor MULT of the doubler and the frequency division factor PLL_R of the R divider, and the frequency of the demodulation signal is obtained. ,in: .

[0021] According to the microwave frequency requirements of the CPT atomic clock, the frequency division coefficient of the integer multiple N frequency divider is first set to generate the initial microwave frequency of the CPT atomic clock, which is used to achieve the coarse frequency adjustment range.

[0022] S2: Determine the charge pump current value according to the frequency of the frequency discrimination signal; Specifically, the charge pump current is a key factor in the loop gain of the phase-locked loop. Evaluate the impact of charge pump current on loop performance while incorporating target loop bandwidth and phase margin According to the design requirements, the current is adjusted to achieve a balance between loop bandwidth and phase noise performance, and finally the charge pump current value is determined to ensure that the system maintains stability and noise performance while locking quickly.

[0023] S3: According to the charge pump current value, by setting the numerator frequency division coefficient and the denominator frequency division coefficient, combined with the frequency of the frequency discrimination signal, determine the carrier signal with a center frequency of ; Specifically, according to the requirement of the CPT atomic clock for microwave frequency, the frequency division coefficient PLL_N of the integer multiple N frequency divider is set to generate the initial microwave frequency of the CPT atomic clock; In order to further improve the frequency resolution and adjustment accuracy, the Sigma-Delta fractional frequency division technology is used to determine the center frequency by setting the numerator frequency division coefficient PLL_NUM and the denominator frequency division coefficient PLL_DEN. ,in: .

[0024] This process combines coarse adjustment and fine adjustment, which not only ensures the high accuracy of the center frequency, but also meets the strict requirements of the CPT atomic clock for frequency stability and adjustable range.

[0025] S4: Determine the VCO frequency band and tuning range according to the center frequency; Specifically, according to the center frequency , select the VCO module and set the starting frequency band. Ensure the frequency coverage requirements by adjusting the tuning voltage range to avoid misalignment or switching difficulties caused by too narrow bandwidth. Set the VCO bias current to ensure that the VCO works in the linear region.

[0026] S5: Determine the target bandwidth and phase margin according to the VCO frequency band and tuning range, design a third-order passive loop filter, and obtain loop filter parameters; Specifically, the loop filter order and capacitor and resistor parameters are set by comprehensively considering the loop bandwidth, locking time, phase noise, spurious signals and other index requirements.

[0027] Here, the target bandwidth is determined based on the VCO frequency band and tuning range. , Phase Margin , according to the target bandwidth , Phase Margin , design a third-order passive loop filter. The transfer function of the third-order loop filter is as follows:

[0028] in, , , , .in , It reflects the real poles of the third-order loop filter; The open-loop gain of the phase-locked loop is:

[0029] in, is the phase detector gain factor, is the VCO voltage-controlled gain coefficient, is the frequency division number; Substituting into the open-loop gain, we can get the phase margin under the open-loop gain:

[0030] when When , the loop bandwidth with maximum phase margin can be calculated:

[0031] Introducing Pole Ratio , ; The total capacitance is:

[0032] Combining the above formulas, we can find , , and The value of the third-order loop filter capacitor and resistor parameters can be obtained.

[0033] Then, the VCO output signal is filtered using the third-order loop filter to obtain a filtered carrier signal.

[0034] S6: According to the carrier signal, determine the modulation frequency, determine the maximum frequency deviation, determine the frequency deviation value and adjust the microwave power gain, so as to generate a frequency modulation signal; this step includes the following sub-steps: S61: Use a microwave modulation frequency that is less than 5 times the CPT line width. Consider a modulation frequency of ; Specifically, in the application of CPT atomic clocks, in order to reduce the line width of the CPT resonance spectrum and increase the slope of the discrimination signal without reducing the contrast of the CPT resonance signal, the microwave modulation frequency should be reasonably selected. Under different experimental conditions, the line width of the CPT signal varies from tens of Hz to tens of kHz. In order to obtain a continuous and steady-state CPT signal without distortion, when the microwave source frequency modulates each instantaneous frequency, it should be ensured that the relaxation of the atomic system at that moment and the effect of the radiation field reach a dynamic balance. If the modulation frequency is too fast, the relaxation effect will not have time to establish a dynamic balance, and the CPT signal will be distorted. Usually, the frequency modulation frequency It is taken to be less than 5 times of the CPT line width to ensure that the CPT signal will not be significantly widened by the modulation frequency.

[0035] S62: According to the modulation frequency, determine the maximum frequency deviation as ; Specifically, the maximum frequency deviation of microwave modulation affects the modulation depth, and the modulation depth affects the demodulation result of the phase-sensitive detection of the CPT signal. When the modulation depth is small, the response signal in the optical signal is weak, and it is difficult to demodulate the CPT signal. If the modulation depth is appropriately increased, the signal-to-noise ratio of the demodulated signal will increase rapidly, and the slope of the demodulation signal will increase. In order to obtain a CPT demodulation signal with a high signal-to-noise ratio and a high demodulation slope, the maximum frequency deviation is determined to be .

[0036] S63: According to the modulation frequency and the maximum frequency deviation, each modulation period is divided into M sampling points, each 360° corresponds to sampling points, thereby obtaining a frequency deviation of each sampling point, and determining frequency deviation values ​​corresponding to all sampling points in a period based on the frequency deviation; Specifically, according to theory, the frequency deviation will show a sinusoidal change in each modulation cycle. This change requires accurate recording of signal characteristics during the frequency modulation process to ensure that the generated signal is consistent with expectations. To achieve this goal, the modulated signal needs to be sampled. The choice of the number of sampling points directly affects the accurate restoration of the signal and the performance of the system. The more sampling points there are, the more accurately the frequency deviation and phase information of the signal can be characterized, but it will also increase the calculation and storage pressure of the microprocessor, especially when the registers of the phase-locked loop chip are frequently updated. On the contrary, too few sampling points may lead to incomplete signal reconstruction and distortion of the demodulated value of the frequency deviation during the modulation process, thereby affecting the stability and accuracy of the system. Assume that each modulation cycle is divided into M sampling points, corresponding to each 360° sampling points. The frequency deviation of each sampling point It can be calculated by the following formula:

[0037] in, is the frequency deviation, M is the number of sampling points, n is the sequence number of the current sampling point.

[0038] Through the above formula, the frequency deviation value corresponding to all sampling points in a cycle can be generated, such as Figure 3 shown.

[0039] S64: according to the frequency deviation value, convert each frequency deviation value into a parameter value array corresponding to the RF generator register at different times; the single chip microcomputer periodically queries the frequency deviation value in the array through a timer, and writes the frequency deviation value into the RF generator register to generate a discrete sinusoidal frequency modulation signal that meets the requirements; S65: According to the generated discrete sinusoidal FM signal, combined with the output power range, considering the signal power attenuation caused by PCB circuit board wiring, set the power amplifier gain to ensure that the output carrier strength meets the CPT atomic clock requirements; Specifically, in the application of CPT atomic clocks, when half-wave modulation is used, it is necessary to set a suitable modulation index to maximize the ±1-level sideband light intensity, and use symmetrical sidebands to achieve CPT resonance, which also helps to reduce the optical frequency shift. Generally, the most convenient and effective way to optimize the modulation index is to adjust the output power of the microwave signal. Combined with the output power range, considering the signal power attenuation caused by PCB circuit board wiring, the power amplifier gain is set to ensure that the output microwave intensity meets the laser frequency locking requirements.

[0040] It can be seen from the above embodiments that the present application adopts direct digital frequency synthesis technology, combined with the discrete FSK function of the digital phase-locked loop chip, to achieve continuous switching of multiple carrier frequencies. Compared with the existing frequency modulation schemes based on analog circuits (such as sine wave modulation and triangle wave modulation), this scheme overcomes the problems of difficult debugging, complex implementation and large frequency deviation, and significantly improves the short-term frequency stability of the CPT atomic clock. At the same time, without increasing the complexity of the hardware, the scheme can flexibly adjust the modulation depth and frequency using a microprocessor, further improving the performance of the microwave modulated signal. In addition, the scheme can effectively improve the signal-to-noise ratio of the demodulation signal under a specific modulation index, optimize the narrowband frequency modulation signal, greatly compress the CPT signal line width, and enhance the reliability and stability of the system.

[0041] Corresponding to the aforementioned embodiment of the CPT atomic clock microwave modulation method based on discrete sine wave frequency modulation, the present application also provides an embodiment of a CPT atomic clock microwave modulation device based on discrete sine wave frequency modulation.

[0042] Figure 4 FIG. 1 is a block diagram of a CPT atomic clock microwave modulation device based on discrete sine wave frequency modulation according to an exemplary embodiment. Figure 4 , the device comprises: The first determination module 1 is used to obtain the input frequency, doubler, pre-R divider, doubler and R divider of the phase-locked loop chip to determine the frequency of the frequency discrimination signal; A second determination module 2, used to determine the charge pump current value according to the frequency of the frequency discrimination signal; A third determination module 3 is used to determine the center frequency according to the charge pump current value by setting the numerator frequency division coefficient and the denominator frequency division coefficient in combination with the frequency discrimination signal frequency; A fourth determination module 4 is used to determine a VCO frequency band and a tuning range according to the center frequency; A fifth determination module 5 is used to determine the target bandwidth and phase margin according to the VCO frequency band and tuning range, design a third-order passive loop filter, filter the VCO output signal, and obtain a filtered carrier signal; The generating module 6 is used to determine the modulation frequency, the maximum frequency deviation, the frequency deviation value and adjust the microwave power gain according to the carrier signal, so as to generate a frequency modulation signal.

[0043] Regarding the device in the above embodiment, the specific manner in which each module performs operations has been described in detail in the embodiment of the method, and will not be elaborated here.

[0044] For the device embodiment, since it basically corresponds to the method embodiment, the relevant parts can refer to the partial description of the method embodiment. The device embodiment described above is only schematic, wherein the units described as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units, that is, they may be located in one place, or they may be distributed on multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the present application scheme. A person of ordinary skill in the art can understand and implement it without paying any creative work.

[0045] Correspondingly, the present application also provides an electronic device, comprising: one or more processors; a memory for storing one or more programs; when the one or more programs are executed by the one or more processors, the one or more processors implement the CPT atomic clock microwave modulation method based on discrete sinusoidal wave frequency modulation as described above.

[0046] Correspondingly, the present application also provides a computer-readable storage medium on which computer instructions are stored. When the instructions are executed by a processor, the CPT atomic clock microwave modulation method based on discrete sine wave frequency modulation as described above is implemented.

[0047] Those skilled in the art will readily appreciate other embodiments of the present application after considering the description and practicing the contents disclosed herein. The present application is intended to cover any modification, use or adaptation of the present application, which follows the general principles of the present application and includes common knowledge or customary techniques in the art that are not disclosed in the present application. The description and examples are intended to be exemplary only, and the true scope and spirit of the present application are indicated by the claims.

[0048] It should be understood that the present application is not limited to the precise structures that have been described above and shown in the drawings, and that various modifications and changes may be made without departing from the scope thereof. The scope of the present application is limited only by the appended claims.

Claims

1. A CPT atomic clock microwave modulation method based on discrete sine wave frequency modulation, characterized in that: include: Obtain the input frequency, doubler, pre-R divider, doubler and R divider of the phase-locked loop chip to determine the frequency of the demodulation signal; Determining a charge pump current value according to the frequency of the frequency discrimination signal; According to the charge pump current value, by setting the numerator frequency division coefficient and the denominator frequency division coefficient, combined with the frequency discrimination signal frequency, the center frequency is determined; Determine the VCO frequency band and tuning range according to the center frequency; According to the VCO frequency band and tuning range, a target bandwidth and phase margin are determined, a third-order passive loop filter is designed, and the VCO output signal is filtered to obtain a filtered carrier signal; According to the carrier signal, the modulation frequency, the maximum frequency deviation, the frequency deviation value and the microwave power gain are determined, thereby generating a frequency modulation signal.

2. According to claim 1, a CPT atomic clock microwave modulation method based on discrete sine wave frequency modulation is characterized in that: Obtain the input frequency of the phase-locked loop chip, the doubler, the pre-R divider, the doubler, and the R divider to determine the frequency of the demodulation signal, including: Get the input frequency of the phase-locked loop chip , the frequency multiplication factor OSC_2X of the doubler, the frequency division factor PLL_R_PRE of the pre-R divider, the frequency multiplication factor MULT of the doubler and the frequency division factor PLL_R of the R divider, and the frequency of the demodulation signal is obtained. ,in: 。 3. The CPT atomic clock microwave modulation method based on discrete sine wave frequency modulation according to claim 1 is characterized in that: Determining a charge pump current value according to the frequency of the frequency discrimination signal includes: According to the frequency of the discrimination signal Evaluate the impact of charge pump current on loop performance while incorporating target loop bandwidth and phase margin According to the design requirements, adjust the current to achieve a balance between loop bandwidth and phase noise performance, and finally determine the charge pump current value.

4. The CPT atomic clock microwave modulation method based on discrete sine wave frequency modulation according to claim 1 is characterized in that: According to the charge pump current value, by setting the numerator frequency division coefficient and the denominator frequency division coefficient, combined with the frequency discrimination signal frequency, the center frequency is determined, including: According to the microwave frequency requirement of the CPT atomic clock, the frequency division coefficient PLL_N of the integer multiple N frequency divider is set to generate the initial microwave frequency of the CPT atomic clock; Using Sigma-Delta fractional frequency division technology, the center frequency is determined by setting the numerator frequency division coefficient PLL_NUM and the denominator frequency division coefficient PLL_DEN. ,in: 。 5. The CPT atomic clock microwave modulation method based on discrete sine wave frequency modulation according to claim 1, characterized in that: According to the center frequency, a VCO frequency band and a tuning range are determined, including: According to the center frequency, select the VCO module and set the starting frequency band. Ensure the frequency coverage requirements by adjusting the tuning voltage range to avoid imbalance or switching difficulties caused by too narrow bandwidth. Set the bias current of the VCO to ensure that the VCO operates in the linear region.

6. The CPT atomic clock microwave modulation method based on discrete sine wave frequency modulation according to claim 1, characterized in that: According to the VCO frequency band and tuning range, the target bandwidth and phase margin are determined, a third-order passive loop filter is designed, and the VCO output signal is filtered to obtain a filtered carrier signal, including: Determine the target bandwidth based on the VCO frequency band and tuning range , Phase Margin , according to the target bandwidth , Phase Margin , design a third-order passive loop filter. The transfer function of the third-order loop filter is as follows: ； in, , , , ,in , It reflects the real poles of the third-order loop filter; The open-loop gain of the phase-locked loop is: ； in, is the phase detector gain factor, is the VCO voltage-controlled gain coefficient, is the frequency division number; Substituting into the open-loop gain, we can get the phase margin under the open-loop gain: ； when When , the loop bandwidth with maximum phase margin can be calculated: ； Introducing Pole Ratio , ; The total capacitance is: ； Combining the above formulas, we can find , , and The value of the third-order loop filter capacitor and resistor parameters are obtained. The third-order loop filter is used to filter the VCO output signal to obtain a filtered carrier signal.

7. The CPT atomic clock microwave modulation method based on discrete sine wave frequency modulation according to claim 1, characterized in that: According to the carrier signal, determining the modulation frequency, determining the maximum frequency deviation, determining the frequency deviation value, and adjusting the microwave power gain, thereby generating a frequency modulation signal, including: S61: Use a microwave modulation frequency that is less than 5 times the CPT line width. Consider a modulation frequency of ; S62: According to the modulation frequency, determine the maximum frequency deviation as ; S63: According to the modulation frequency and the maximum frequency deviation, each modulation period is divided into M sampling points, each 360° corresponds to sampling points, thereby obtaining a frequency deviation of each sampling point, and determining frequency deviation values ​​corresponding to all sampling points in a period based on the frequency deviation; S64: according to the frequency deviation value, convert each frequency deviation value into a parameter value array corresponding to the RF generator register at different times; the single chip microcomputer periodically queries the frequency deviation value in the array through a timer, and writes the frequency deviation value into the RF generator register to generate a discrete sinusoidal frequency modulation signal that meets the requirements; S65: According to the generated discrete sinusoidal FM signal, combined with the output power range, considering the signal power attenuation caused by PCB circuit board wiring, set the power amplifier gain to ensure that the output carrier strength meets the CPT atomic clock requirements.

8. A CPT atomic clock microwave modulation device based on discrete sine wave frequency modulation, characterized in that: include: The first determination module is used to obtain the input frequency of the phase-locked loop chip, the doubler, the pre-R divider, the multiplier and the R divider to determine the frequency of the frequency discrimination signal; A second determination module, used to determine a charge pump current value according to the frequency of the frequency discrimination signal; A third determination module is used to determine the center frequency according to the charge pump current value by setting the numerator frequency division coefficient and the denominator frequency division coefficient in combination with the frequency of the frequency discrimination signal; A fourth determination module, used to determine a VCO frequency band and a tuning range according to the center frequency; A fifth determination module is used to determine the target bandwidth and phase margin according to the VCO frequency band and tuning range, design a third-order passive loop filter, filter the VCO output signal, and obtain a filtered carrier signal; The generating module is used to determine the modulation frequency, the maximum frequency deviation, the frequency deviation value and adjust the microwave power gain according to the carrier signal, so as to generate a frequency modulation signal.

9. An electronic device, characterized in that: include: one or more processors; A memory for storing one or more programs; When the one or more programs are executed by the one or more processors, the one or more processors implement the method according to any one of claims 1 to 7.

10. A computer-readable storage medium having computer instructions stored thereon, characterized in that: When the instruction is executed by a processor, the steps of the method according to any one of claims 1 to 7 are implemented.

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