阅读说明：本技术 一种完整的被动型铷原子钟设计方法和装置 (Method and device for designing complete passive rubidium atomic clock ) 是由 雷海东 于 2021-01-27 设计创作，主要内容包括：本发明涉及被动型铷原子钟设计技术领域,具体地说,涉及一种完整的被动型铷原子钟设计方法和装置。其包括微控制器、卫星时间同步模块、测试系统、频率漂移修正模块、运行可靠性监测模块和部件参数大数据建模。本发明中通过VCXO分频信号与GPS秒脉冲信号做对比,以对频率的偏差检测,另外铷原子频标整机频率输出信号经隔离放大器后,一路用作输出用,另一路送至频率漂移、稳定度测试仪中,与高稳时钟信号做对比,得出原始频差,然后利用微控制器实现对频率的偏差修正的控制。(The invention relates to the technical field of design of a passive rubidium atomic clock, in particular to a method and a device for designing a complete passive rubidium atomic clock. The system comprises a microcontroller, a satellite time synchronization module, a test system, a frequency drift correction module, an operational reliability monitoring module and a component parameter big data modeling. In the invention, a VCXO frequency division signal is compared with a GPS second pulse signal to detect the deviation of the frequency, in addition, after a rubidium atomic frequency standard complete machine frequency output signal passes through an isolation amplifier, one path is used for output, and the other path is sent to a frequency drift and stability tester to be compared with a high-stability clock signal to obtain an original frequency difference, and then, the microcontroller is utilized to realize the control of the deviation correction of the frequency.)

1. A method and a device for designing a complete passive rubidium atomic clock are characterized in that: the system comprises a microcontroller, a satellite time synchronization module, a test system, a frequency drift correction module, an operational reliability monitoring module and a component parameter big data modeling, wherein:

the microcontroller is connected with the satellite time synchronization module; the output end of the satellite time synchronization module is connected with the test system; the output end of the test system is connected with the frequency drift correction module; the output end of the frequency drift correction module is connected with the operation reliability monitoring module; and the output end of the operational reliability monitoring module is connected with the component parameter big data in a modeling mode.

2. The complete passive rubidium atomic clock design device as claimed in claim 1, wherein: the test system comprises a field intensity test module and a stability test module; the input end of the field intensity test module is connected with the satellite time synchronization module; the output end of the field intensity testing module is connected with the stability testing module; the field intensity test module and the stability test module are both connected with the microcontroller in a bidirectional way; and the output end of the stability testing module is connected with the frequency drift correction module.

3. The complete passive rubidium atomic clock design device as claimed in claim 1, wherein: the satellite time synchronization module comprises a temperature compensation module, a crystal oscillation module, a DDS frequency division module, a GPS receiving module, a quantum system, a phase discriminator and a short stability module, wherein:

the input end of the crystal oscillation module is connected with the microcontroller, and the output end of the crystal oscillation module outputs a frequency signal to the DDS frequency division module and the short-stability module through the isolation amplifier so as to transmit the signal to the quantum system through the short-stability module; the output end of the DDS frequency division module is connected with the phase discriminator; the output end of the phase discriminator is connected with the crystal oscillation module; the input end of the phase discriminator is connected with the GPS receiving module; the input end of the crystal oscillation module is also connected with the temperature compensation module in a bidirectional mode.

4. The complete passive rubidium atomic clock design device as claimed in claim 3, wherein: the short stable module comprises a VCXO, a time correction module, a servo module and a voltage control correction module, wherein:

the output end of the VCXO is connected with the quantum system to form a traditional electronic circuit; the output end of the quantum system is connected with the servo module; the output end and the input end of the servo module are respectively connected with the voltage control correction module and the time correction module; the output end of the voltage control correction module is connected with the VCXO; the output end of the VCXO is also connected with the time correction module; the input end of the time correction module is also connected with the GPS receiving module.

5. The complete passive rubidium atomic clock design device as claimed in claim 2, wherein: the field intensity testing module comprises an optical field testing module, a microwave field testing module, a magnetic field testing module, a temperature field testing module and an electric field testing module.

6. The complete passive rubidium atomic clock design device as claimed in claim 1, wherein: the frequency drift correction module comprises a frequency drift stability tester, a rubidium atomic frequency standard physical system, a magnetic field constant current source driving module and a D/A converter.

7. A complete passive rubidium atomic clock design method, comprising the complete passive rubidium atomic clock design device as claimed in any one of claims 1-6, wherein: the method comprises the following steps:

s1, satellite time synchronization: the GPS receiver receives a frequency signal from a GPS antenna, and performs phase discrimination with a frequency signal obtained by frequency division of the frequency signal generated in the crystal oscillator by the DDS frequency divider 1/1000 and the frequency signal generated by the GPS receiver;

s2, field strength test: detecting the field intensity of the atomic clock by using an optical field test module, a microwave field test module, a magnetic field test module, a temperature field test module and an electric field test module;

s3, stability test: evaluating the stability index of the detected frequency source, and selecting a signal source with the same level or higher level than the detected frequency source as a compensation detection quantity source;

s4, frequency drift correction: and (3) assuming the daily stability and the magnitude of daily drift by using a rubidium atomic frequency standard, and correcting according to the daily stability and the magnitude of daily drift.

8. The complete passive rubidium atomic clock design method as claimed in claim 7, wherein: the optical field test module in S2 adopts an optical pumping method to improve the signal-to-noise ratio of the passive rubidium atomic clock, and the energy level shift of pumping light to the passive rubidium atoms is as follows:

wherein P is a dipole moment operator; e is the complex amplitude of the time optical electric field, and gamma is the service life of the alpha excited state; e_αIs in an excited state; e_iEnergy in the ground state energy level.

9. The complete passive rubidium atomic clock design method as claimed in claim 7, wherein: the rubidium atom frequency standard in the S4 adopts a spiral tube current mode, and a calculation formula of the magnitude of a magnetic field generated by the current is as follows:

wherein n is the number of turns per unit length of the coil; i is the electrifying current;is constant 10^-7。

10. The design method of a complete passive rubidium atomic clock as claimed in claim 9, wherein: the calculation formula of the number of turns of the coil in unit length is as follows:

wherein m is the number of turns of the magnetic field winding; r is the radius of the winding.

Technical Field

The invention relates to the technical field of design of a passive rubidium atomic clock, in particular to a method and a device for designing a complete passive rubidium atomic clock.

Background

With the development of the aviation field in China, almost a plurality of artificial earth satellites rise to the outer space every year, and the development of space technologies such as a launching system, navigation, carrier rocket navigation, a missile system, wireless communication, television broadcasting, transceiving split radar, GPS and the like of the artificial earth satellites has higher and higher requirements on the long-term accuracy and the short-term accuracy and the stability of the adopted frequency and time reference.

Because the rubidium radiation frequency has long-time stability, the resonance frequency of the passive rubidium atom is determined as the reference frequency by the frequency standard, the rubidium atom frequency standard used as the frequency standard and the time standard has the characteristics of low drift, high stability, radiation resistance, small volume, light weight, low power consumption and the like, the travel time error of the passive rubidium atomic clock with extremely high accuracy is not more than 1s in 370 ten thousand years

However, the 1pps signal output by the passive rubidium atom is obtained by frequency division of the rubidium oscillator frequency signal and is synchronized with the UTC time output by the GPS, but a frequency hopping phenomenon occurs during synchronization, and a frequency deviation may occur, but the deviation cannot be detected and corrected in time.

Disclosure of Invention

The invention aims to provide a complete passive rubidium atomic clock design method and a device, so as to solve the problems in the background technology.

In order to achieve the above object, the present invention provides a method and an apparatus for designing a complete passive rubidium atomic clock, including a microcontroller, a satellite time synchronization module, a test system, a frequency drift correction module, an operational reliability monitoring module, and a component parameter big data modeling, wherein:

the microcontroller is connected with the satellite time synchronization module; the output end of the satellite time synchronization module is connected with the test system; the output end of the test system is connected with the frequency drift correction module; the output end of the frequency drift correction module is connected with the operation reliability monitoring module; and the output end of the operational reliability monitoring module is connected with the component parameter big data in a modeling mode.

As a further improvement of the technical scheme, the test system comprises a field strength test module and a stability test module; the input end of the field intensity test module is connected with the satellite time synchronization module; the output end of the field intensity testing module is connected with the stability testing module; the field intensity test module and the stability test module are both connected with the microcontroller in a bidirectional way; and the output end of the stability testing module is connected with the frequency drift correction module.

As a further improvement of the technical solution, the satellite time synchronization module includes a temperature compensation module, a crystal oscillation module, a DDS frequency division module, a GPS receiving module, a quantum system, a phase discriminator, and a short stabilization module, wherein:

the input end of the crystal oscillation module is connected with the microcontroller, and the output end of the crystal oscillation module outputs a frequency signal to the DDS frequency division module and the short-stability module through the isolation amplifier so as to transmit the signal to the quantum system through the short-stability module; the output end of the DDS frequency division module is connected with the phase discriminator; the output end of the phase discriminator is connected with the crystal oscillation module; the input end of the phase discriminator is connected with the GPS receiving module; the input end of the crystal oscillation module is also connected with the temperature compensation module in a bidirectional mode.

As a further improvement of the present technical solution, the short stabilization module includes a VCXO, a time correction module, a servo module, and a voltage control correction module, wherein:

the output end of the VCXO is connected with the quantum system to form a traditional electronic circuit; the output end of the quantum system is connected with the servo module; the output end and the input end of the servo module are respectively connected with the voltage control correction module and the time correction module; the output end of the voltage control correction module is connected with the VCXO; the output end of the VCXO is also connected with the time correction module; the input end of the time correction module is also connected with the GPS receiving module.

As a further improvement of the technical scheme, the field intensity testing module comprises an optical field testing module, a microwave field testing module, a magnetic field testing module, a temperature field testing module and an electric field testing module.

As a further improvement of the technical scheme, the frequency drift correction module comprises a frequency drift stability tester, a rubidium atomic frequency standard physical system, a magnetic field constant current source driving module and a D/A converter.

The second purpose of the present invention is to provide a complete passive rubidium atomic clock design method, including any one of the above complete passive rubidium atomic clock design devices, including the following method steps:

s1, satellite time synchronization: the GPS receiver receives a frequency signal from a GPS antenna, and performs phase discrimination with a frequency signal obtained by frequency division of the frequency signal generated in the crystal oscillator by the DDS frequency divider 1/1000 and the frequency signal generated by the GPS receiver;

s2, field strength test: detecting the field intensity of the atomic clock by using an optical field test module, a microwave field test module, a magnetic field test module, a temperature field test module and an electric field test module;

s3, stability test: evaluating the stability index of the detected frequency source, and selecting a signal source with the same level or higher level than the detected frequency source as a compensation detection quantity source;

s4, frequency drift correction: and (3) assuming the daily stability and the magnitude of daily drift by using a rubidium atomic frequency standard, and correcting according to the daily stability and the magnitude of daily drift.

As a further improvement of the technical solution, in S2, the optical field test module adopts an optical pumping method to improve the signal-to-noise ratio of the passive rubidium atomic clock, and the energy level shift of pumping light to the passive rubidium atom is:

wherein P is a dipole moment operator; e is the complex amplitude of the time optical electric field, and gamma is the service life of the alpha excited state; e alpha is an excited state; e_iEnergy in the ground state energy level.

As a further improvement of the technical solution, the rubidium atom frequency standard in S4 adopts a spiral tube current mode, and a calculation formula of the magnitude of the magnetic field generated by the current is as follows:

wherein n is the number of turns per unit length of the coil; i is the electrifying current;is constant 10^-7。

As a further improvement of the present technical solution, a calculation formula of the number of turns per unit length of the coil is as follows:

wherein m is the number of turns of the magnetic field winding; r is the radius of the winding.

Compared with the prior art, the invention has the beneficial effects that: the frequency deviation of the frequency is detected by comparing a VCXO frequency division signal with a GPS second pulse signal, in addition, after a rubidium atomic frequency standard complete machine frequency output signal passes through an isolation amplifier, one path is used for output, and the other path is sent to a frequency drift and stability tester to be compared with a high-stability clock signal, so that an original frequency difference is obtained, and then the microcontroller is used for realizing the control of the frequency deviation correction.

Drawings

FIG. 1 is an overall block diagram of the present invention;

FIG. 2 is a block diagram of a crystal oscillation module according to the present invention;

FIG. 3 is a first schematic circuit diagram of a temperature compensation module according to the present invention;

FIG. 4 is a second schematic circuit diagram of the temperature compensation module according to the present invention;

FIG. 5 is a block diagram of a DDS frequency division module of the present invention;

FIG. 6 is a block diagram of a VCXO correction module according to one embodiment of the present invention;

FIG. 7 is a block diagram of a VCXO correction module according to a second embodiment of the present invention;

FIG. 8 is a schematic diagram of the comparison between the VCXO frequency signal and the GPS second pulse of the present invention;

FIG. 9 is a block diagram of an atomic clock synchronization module of the present invention;

FIG. 10 is a comparison of the VCXO divided signal, the GPS second pulse, and the local reference source signal of the present invention;

FIG. 11 is a comparison of the VCXO divided signal, the GPS second pulse, and the local reference source signal of the present invention;

fig. 12 is a schematic circuit diagram of the VCXO divided signal and local reference source signal of the present invention;

fig. 13 is a block diagram of a rubidium atomic frequency standard module according to the present invention;

FIG. 14 is a diagram of a function of a detected signal according to the present invention;

FIG. 15 is a schematic diagram of a spectral lamp circuit of the present invention;

FIG. 16 is a plot of the magnetic field as a function of center frequency for the present invention;

FIG. 17 is a schematic diagram of a servo circuit according to the present invention;

FIG. 18 is a diagram illustrating the high and low level transitions of the optical detection signal according to the present invention;

FIG. 19 is a graph of the microwave power function according to one embodiment of the present invention;

FIG. 20 is a graph of the microwave power function of the present invention;

FIG. 21 is a schematic diagram of a negative feedback constant current source circuit according to the present invention;

FIG. 22 is an overall flow chart of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Referring to fig. 1-22, the present invention provides a technical solution:

the invention provides a method and a device for designing a complete passive rubidium atomic clock, which comprises a microcontroller, a satellite time synchronization module, a test system, a frequency drift correction module, an operation reliability monitoring module and a component parameter big data modeling, wherein the method comprises the following steps:

referring to fig. 2, the microcontroller is connected to the satellite time synchronization module; the output end of the satellite time synchronization module is connected with the test system; the output end of the test system is connected with the frequency drift correction module; the output end of the frequency drift correction module is connected with the operation reliability monitoring module; and the output end of the operational reliability monitoring module is connected with the component parameter big data in a modeling mode.

In addition, the test system comprises a field strength test module and a stability test module; the input end of the field intensity test module is connected with the satellite time synchronization module; the output end of the field intensity testing module is connected with the stability testing module; the field intensity test module and the stability test module are both connected with the microcontroller in a bidirectional way; and the output end of the stability testing module is connected with the frequency drift correction module.

Further, the satellite time synchronization module includes a temperature compensation module, a crystal oscillation module, a DDS frequency division module, a GPS receiving module, a quantum system, a phase discriminator, and a short stabilization module, wherein:

referring to fig. 2, an input end of the crystal oscillation module is connected to the microcontroller, and an output end of the crystal oscillation module outputs a frequency signal to the DDS frequency division module and the short stabilization module through the isolation amplifier, wherein a reference frequency signal of the DDS frequency division module may be a frequency signal generated by the crystal oscillation module itself, as shown in fig. 5, so as to transmit the signal to the quantum system through the short stabilization module; the output end of the DDS frequency division module is connected with the phase discriminator; the output end of the phase discriminator is connected with the crystal oscillation module; the input end of the phase discriminator is connected with a GPS receiving module to form a PLL loop, the GPS receiving module preferably adopts a Jupiter 12 series TU35-D410-021 GPS module as a GPS receiver core part, and the module provides a 10KHz frequency output synchronous with 1PPS signals; the input end of the crystal oscillation module is also connected with the temperature compensation module in a bidirectional mode.

In addition, as shown in fig. 3, the bridge circuit temperature measurement in the temperature compensation module mainly includes two R with the same resistance value, a thermistor sensor Ro with a preset temperature value and a temperature measurement thermistor Rk, and is divided into the following two cases:

when the temperature of the working environment of the semiconductor component is constant, that is, the measured value of the thermistor Rk is equal to the preset value Ro, the output voltage difference at the end of the resistor bridge A, B is 0, and the output of the whole temperature compensation output end Uout is 0;

when the working environment temperature of the semiconductor component changes, a certain voltage difference is formed at A, B ends of the bridge circuit, the voltage difference is transmitted to A3 through the voltage followers A1 and A2 for differential amplification, and the amplified voltage difference can be effectively collected, so that a gain linear regulating circuit A4 is added at the output end of the differential amplification A3, the obtained temperature compensation voltage difference Uout is transmitted to a microprocessor for processing, and acts on a varactor diode D2 connected in series with a crystal oscillator through a voltage-controlled voltage 2, and the nonlinear frequency drift of the crystal oscillator is compensated through the change of the capacitance of the series connection of the crystal oscillator.

In addition, the crystal oscillation module is composed of a thermistor R1, a varactor diode D1, D2, D3 and a basic oscillation oscillator circuit, as shown in fig. 4, R1 is connected in series with the crystal oscillator in the oscillator, and when the constant temperature control temperature changes, the resistance value of the thermistor and the capacitance value of the equivalent series capacitor of the crystal correspondingly change, so as to counteract or reduce the temperature drift of the oscillation frequency.

The signal from the GPS receiver and the signal generated by the crystal oscillation pass through a phase discriminator to obtain a GPS deviation correction signal, namely, a voltage-controlled voltage 1 acts on a variable capacitance diode D1 connected in series with the crystal oscillator, and the nonlinear frequency drift of the crystal oscillator is compensated through the change of the series capacitance of the crystal oscillator.

The bridge type pressure difference signal from the temperature compensation module reflects the working environment temperature information of peripheral components of the crystal oscillation module, and after being fed to the microprocessor, the bridge type pressure difference signal is processed to obtain a voltage-controlled voltage 2 which acts on a variable capacitance diode D2 connected in series with the crystal oscillator, and the nonlinear frequency drift of the crystal oscillator is compensated through the change of the series capacitance of the crystal oscillator.

The quantum deviation rectifying signal from the quantum system reflects that 10MHz signal of the crystal oscillation module is transmitted to the quantum system, and then is subjected to frequency doubling and synthesis of the atomic frequency standard circuit part, and whether the microwave frequency is aligned with the 0-0 transition frequency information of the atomic ground state after microwave frequency mixing is processed to obtain a voltage-controlled voltage 3 which acts on a variable capacitance diode D3 connected in series with the crystal oscillator, and the deviation rectifying is performed on the output 10MHz signal frequency of the crystal oscillator through the change of the series capacitance of the crystal oscillator.

Specifically, the short-time stable module comprises a VCXO, a time correction module, a servo module and a voltage control correction module, wherein:

the output end of the VCXO is connected with the quantum system to form a traditional electronic circuit; the output end of the quantum system is connected with the servo module; the output end and the input end of the servo module are respectively connected with the voltage control correction module and the time correction module; the output end of the voltage control correction module is connected with the VCXO; the output end of the VCXO is also connected with the time correction module; the input end of the time correction module is also connected with the GPS receiving module.

It should be noted that, referring to fig. 6 and 7, during GPS correction, a receiver obtains a signal sent by a GPS satellite, obtains a pulse-per-second signal after conversion processing, sends the pulse-per-second signal to a time correction module, counts a frequency signal output by a VCXO within a period of the pulse-per-second signal and obtains a corresponding correction value, sends the correction value to a servo module, outputs a corresponding dc correction voltage to act on the VCXO through a voltage control correction module, and starts VCXO frequency signal counting when a GPS pulse-per-second gate signal width shown in fig. 8 is at a high level and a rising edge of a first pulse of the VCXO frequency signal starts at T1, and starts the counting of the VCXO frequency signal when a GPS pulse gate low level arrives after T seconds and does not stop counting, and stops the counter when a time T2 elapses until a rising edge of a subsequent VCXO frequency signal arrives, and the counter is closed, where the time width of the enable signal is enabled, equal to the number N of complete cycles of the VCXO frequency signal; then according to the relevant parameters: t, t1, t2 and N, the servo module can obtain the corresponding correction value of the VCXO frequency signal according to the traditional GPS time difference ratio, and outputs the corresponding direct current correction voltage to act on the VCXO through the voltage control correction module.

In addition, the atomic clock is synchronized to the GPS signal to form local clock synchronization, and as shown in fig. 9, the signal obtained by dividing the frequency of the VCXO by the DDS, the local reference source, and the GPS second pulse are all transmitted to the delay array module. Here, the local reference source usually selects a high-stability H-clock source, the frequency of its output signal is usually 10MHz, and the frequency of the VCXO we select is also 10MHz, and a frequency signal of 1MHz is obtained after frequency division by DDS, where the timing sequence corresponding to the principle of the delay array module is shown in fig. 10.

When the preset GPS second pulse gate signal arrives at a high level, the rising edge of the first pulse of the VCXO frequency division signal enables the enabling ends of the counter 1 and the counter 2 to be effective, and counts the VCXO frequency division signal and the local reference signal respectively, when the preset GPS second pulse gate signal arrives again after T seconds, the two counters do not stop counting at the moment, the two counters are closed simultaneously until the rising edge of the subsequent VCXO frequency division signal arrives, and the time width of the enabling signal is just equal to the complete period number of the VCXO frequency division signal.

Assuming that the frequency of the VCXO frequency-divided signal is Fx and the frequency of the local reference source signal is fo, the counter counts the VCXO frequency-divided signal and the local reference source signal respectively as N1 and N2 during the gate time T, the frequency Fx of the VCXO frequency-divided signal is related to the local reference source frequency fo and the count values N1 and N2 of the two counters, it is noted that since the frequencies of the VCXO frequency-divided signal and the local reference signal are different, the phases of the VCXO frequency-divided signal and the local reference signal are unlikely to overlap and be equal at point A, B, and the VCXO frequency-divided signal and the local reference signal are represented by the "phase difference measurement diagram" shown in fig. 11, wherein:

when the gate signal trigger edge pulse of the GPS second pulse arrives, the rising edge of the next local reference signal is waited, the corresponding counter is enabled to carry out operations of 'start counting' and 'end counting' at the points A and B at the moment, then the time difference delta t1, delta t2 exists between the time points A and B of the counter and the next edge pulse of the local reference signal, the specific difference value depends on the phase difference value of the local reference signal and the local reference signal at the time point A or the time point B, and the specific difference value is not in a constant fixed phase difference relation, different errors exist in each sampling, and for clock frequency sources with high stability and high frequency, a further improved measurement method is needed to determine the values delta t1 and delta t2 so as to improve the measurement accuracy. At this time, we adopt the following solution:

the VCXO frequency division signal and the local reference signal are also respectively sent to a not gate array, N stages are set in the not gate array, N is an even number, the not gate and an and gate are generated by an internal FPGA chip in an analog manner, when a moment comes, the VCXO frequency division signal respectively passes through 2 not gates, 4 not gates and 6 not gates of the not gate array, and then respectively passes through an and gate together with the local reference source signal, as shown in fig. 12;

when the time A or the time B arrives, the AND gate is identified as '1' by the state 1 detection module only after waiting until the high level of the local reference signal arrives by the AND operation: for example, when the time a arrives, since the VCXO frequency-divided signal is at a high level, that is, in a "1" state, after N ═ 6 not gates in fig. 7 are delayed, the high level of the local reference source signal comes, so that the corresponding and gate is operated as "1", and the previous and gates in N ═ 2 and N ═ 4 are both operated as "0"; in this way, the magnitude of Δ t can be obtained by detecting the N value of 1 by the and gate operation corresponding to the state "1" detection module, and the magnitude of Δ t2 can be obtained in the same manner.

And obtaining a frequency correction value of the VCXO frequency division signal through accurate measurement according to the obtained delta t1 and delta t2, and outputting a corresponding direct current correction voltage to act on the VCXO through the voltage control correction module.

In addition, the field intensity test module comprises an optical field test module, a microwave field test module, a magnetic field test module, a temperature field test module and an electric field test module.

When a pumping light pulse passes through a rubidium atom frequency standard integrated filtering resonance bubble, rubidium atoms in the absorption bubble are concentrated on five sub-energy levels of F ═ 2, then two coherent microwave pulses with certain time intervals are used for acting on the rubidium atoms, and the microwave frequency is exactly equal to the transition frequency of the rubidium atom ground state 0-0. When the second microwave pulse acts, the spectrum lamp is simultaneously lightened, on the basis of keeping the microwave pulse, sampling light detection is carried out through the microprocessor, after the light detection is finished, the microwave pulse and the spectrum lamp are closed, quantum rectification information is transmitted to the microwave interrogation signal generating circuit, the servo of the whole machine is finished, and the sequence of the whole process and the pulse pumping light generating principle circuit are repeated as shown in fig. 14 and 15.

In addition, for pumping light with different sizes and the same spectral line type, the difference frequency value change caused by the cavity temperature change is different, the slope of the 70% light intensity curve is smaller than that of the 100% light intensity curve, that is, for 70% light intensity, the frequency shift caused by the cavity temperature change is smaller than that of the 100% light intensity, if the light intensity is further reduced (such as 50% light intensity and 30% light intensity …), a better slope light intensity can be obtained, but because the signal-to-noise ratio of the system is considered, a very small light intensity cannot be selected, and at this time, the light intensity with a zero temperature coefficient needs to be obtained by changing the proportion and the pressure of the buffer gas in the integrated filter resonance bubble.

And a magnetic hyperfine component optical filter is added at the rear stage of the emission light path of the spectrum lamp, so that the light intensity of the spectrum lamp required in the theory can be controlled well, and the spectral line shape of the pumping light can be improved, so that the spectral line shape of the pumping light is completely symmetrical around the central frequency, and the generation of light frequency shift is reduced.

In order to reduce the microwave power frequency shift and the negative contribution of the microwave power frequency shift to the overall stability, the microwave field testing module works in the aspects of reducing the microwave power frequency shift coefficient and stabilizing the microwave power respectively, and comprises two parts:

coarse adjustment: the power value of the microwave source is directly changed by the central processing unit to obtain three or more values of P1, P2 and P3, in this embodiment, P1, P2 and P3 are selected, please refer to fig. 16, the central processing unit first controls the microwave source to output a power value P1, the current control module acts on the magnetism to obtain the magnetic field size C1, at this time, the central processing unit controls the microwave source to change the output microwave frequency size to sweep frequency near the transition center frequency of 0-0 of the atomic ground state hyperfine structure, and simultaneously, the corresponding optical detection signal is obtained by the photoelectric detection module, so that the center frequency value f11 of the atomic spectral line can be obtained according to the traditional technology.

And at the moment, ensuring that the power value P1 is unchanged, sequentially changing the magnetic field to C2 and C3 values, and obtaining corresponding atomic spectral line center frequency values f12 and f13 according to the method. Thus, a set of variation relationships of the magnetic field C of the detection system and the central frequency f at the value of the microwave power P1 can be obtained. For the same reason, changing the microwave power values P to P2 and P3 will obtain a plurality of sets of variation relationships between C and the center frequency f.

Fine adjustment: in order to eliminate the harmful effect of microwave power frequency-.

Wherein, A1 and A4 complete the detection of the maximum peak value of the optical detection signal:

when the voltage of the photo-detection signal is greater than the voltage of the capacitor C1, a voltage drop is generated on the resistor Rf, the current cannot be conducted according to the virtual disconnection rule D11 from left to right, and the charging current is conducted on the C1 through the D12. When the voltage of the photo detection signal is lower than the voltage of the capacitor C1, a voltage drop occurs across the resistor R2 and the current flows from right to left. According to the virtual break rule of the operational amplifier, D12 is not conducted, and the current only enters A1 through D11. Because the output voltage of the voltage follower A4 is the same as the voltage on the capacitor C1, the diode D11 is cut off, the capacitor can not discharge through the D11, and the voltage is protected, namely the capacitors C1 and A4 output V1 to record the maximum peak value of the light detection signal.

The capacitor C1 has a discharge resistor R1, the discharge time constant τ of the RC is set according to the period of the actual photodetection signal, for example, if the frequency of the photodetection signal is 79Hz, τ is 1S;

a3 completes the optical detection signal inversion:

because small modulation is added on the microwave interrogation signal, the microwave interrogation signal is subjected to frequency discrimination processing by a physical system, the valley value and the peak value of the optical detection signal 1 are both positive, when the peak value is detected, the optical detection signal is inverted by an operational amplifier A3 to obtain the signal output shown in 2 in figure 4, and then a negative amplitude direct current level Vref is superposed to finally complete the conversion of the high level and the low level of the optical detection signal, as shown in figure 18;

a2 and A5 complete the detection of the minimum peak of the optical detection signal:

the photodetection signal is processed by A3 and sent to the non-inverting terminal of the operational amplifier a2, wherein the principles of a2 and a5 are as described above in a1 and A3, except that at this time, since the photodetection signal has been processed by the operational amplifier A3, detection of the minimum value of the photodetection signal is performed by a2 and a 5.

A6 completes the detection of the peak:

the processed photodetection signals with high level V11 and low level V12 are respectively sent to a differential amplifier A6, and (V12-V11) × (Ry/Rx) is output by adjusting the ratio of Ry to Rx;

when the microwave power changes, the overall frequency output by the atomic clock and the amplitude of the optical detection signal processed by the servo loop all change and are in a proportional relationship, as shown in fig. 19 and 20, for example: when the microwave power is increased at a certain moment, the whole frequency output by the atomic clock is increased by delta f, and after the traditional atomic clock synchronous phase discrimination, the voltage-controlled local oscillator output frequency is increased, error correction is generated, and the microwave power frequency shift is generated fundamentally.

The amplitude of the optical detection signal is increased due to the increase of the microwave power, and V1 is increased after the peak value detection of the optical detection signal, so that (K0V0-K1V1) is reduced, the voltage-controlled voltage output to the voltage-controlled local oscillator is reduced, the output frequency of the voltage-controlled local oscillator is reduced, and compensation is performed, namely, a negative frequency offset Δ f1 is generated, which is equivalent to the action of the positive frequency offset Δ f, which is caused by the increase of the microwave power and leads to the increase of the overall frequency of the atomic clock output, if the proportional relation in the good formula (1) is controlled, the Δ f- Δ f1 can be made 0, namely, the influence of the overall microwave power frequency shift is overcome.

In addition, the frequency drift correction module comprises a frequency drift stability tester, a rubidium atomic frequency standard physical system, a magnetic field constant current source driving module and a D/A converter.

Please refer to the rubidium atomic frequency standard complete machine frequency output signal shown in fig. 13, after passing through the isolation amplifier, the frequency deviation is detected by comparing the VCXO frequency division signal with the GPS second pulse signal, and after passing through the isolation amplifier, one path of the rubidium atomic frequency standard complete machine frequency output signal is used as an output, and the other path of the rubidium atomic frequency standard complete machine frequency output signal is sent to a frequency drift and stability tester, and compared with a high stable clock signal, so as to obtain an original frequency difference, and then a microcontroller is used to realize the control of frequency deviation correction, which is the basis of the so-called frequency stability and drift test; the drift amount of the frequency standard is sampled by taking day as a period, so that the frequency drift stability tester transmits the drift amount of the rubidium atom frequency to the microcontroller through an RS232 port by taking day as a unit.

The ground state hyperfine 0-0 transition frequency of the rubidium atoms in the integrated bubble is the frequency discrimination reference frequency f0 of the frequency standard of the rubidium atoms. The rubidium atom moving direction in the integrated filtering resonance bubble is disordered, and a magnetic field with fixed current magnitude and direction is added, so that the effects of atom splitting and quantization axis can be well played.

For the⁸⁷For the non-0 transition, the frequency of the Rb atom is more sensitive to the magnetic field H, while for the 0-0 transition, the frequency f0 is only proportional to the power of H, independent of the power of H, and is less sensitive to the external magnetic field.

The microcontroller selects a corresponding digital set value of the D/A voltage control quantity according to a pre-stored reference quantity of 'drift quantity df-C field current quantity I', and sends the digital set value to the C field constant current source driving module through the D/A module. For example: for a high-precision stable rubidium atomic frequency standard, the daily stability and daily drift are assumed to be 1E-14 orders, the correction amount at each time should be far less than 1E-14, and 5E-15 can be selected for correction.

The constant current source part is an independent linear negative feedback constant current source, as shown in fig. 21:

u1(LM350A) is the core part of regulator, is the constant current source, and load current produces weak sampling voltage through sampling resistance R5, and through the cophase of ultra low noise operational amplifier U2 and enlargies. The amplified voltage signal is sent to the negative terminal of a differential amplifier consisting of U3. The differential amplifier amplifies the difference between the sampling voltage at the negative end and the setting voltage of the microprocessor at the positive end, and outputs the amplified difference to the adjusting end of the adjuster to form closed-loop feedback. If the load current is increased under certain conditions, the voltage on the sampling resistor is increased, the output voltage of the in-phase amplifier U2 is increased, the output voltage of the differential amplifier is decreased, the voltage at the voltage regulated by the regulator is decreased, the output voltage of the regulator is decreased, the load current is decreased, and the dynamic stability of the load current is maintained, and vice versa. It can be seen that the positive side microprocessor setting of the differential amplifier determines the magnitude of the load current. If the voltage of the positive terminal of the U3 rises, namely the set value of the microprocessor rises, the voltage of the regulator regulating terminal rises, the voltage of the regulator output rises, the load current increases, the output of the in-phase amplifier increases, the voltage of the negative terminal of the differential amplifier rises until the voltage of the positive terminal and the voltage of the negative terminal of the U3 are equal, and the system is dynamically stabilized again.

The sampling resistor is connected in series in the load loop and detects the change of the load current, so the stability of the sampling resistor directly influences the performance of the constant current source, and the sampling resistor has enough power, otherwise the performance of the constant current source is influenced and even burnt out; in an actual circuit, a precise resistor made of a high-power manganin material is selected, and an ultra-low noise operational amplifier AD797 is selected as a sampling amplifier U2; because it is in the first stage of closed loop feedback, the effect of noise is minimized; the differential amplifier U3 adopts a high-precision operational amplifier OP07 to provide a high-precision comparison result; d4 is to prevent the reverse induced voltage from occurring in the circuit and damaging the circuit due to the long lead; the addition of D4 makes the reverse induced voltage form a closed loop through D4, thereby protecting the circuit.

A second objective of the present invention is to provide a method for designing a complete passive rubidium atomic clock, including any one of the above devices, including the following steps:

s1, satellite time synchronization: the GPS receiver receives a frequency signal from a GPS antenna, and performs phase discrimination with a frequency signal obtained by frequency division of the frequency signal generated in the crystal oscillator by the DDS frequency divider 1/1000 and the frequency signal generated by the GPS receiver;

s2, field strength test: detecting the field intensity of the atomic clock by using an optical field test module, a microwave field test module, a magnetic field test module, a temperature field test module and an electric field test module;

s3, stability test: evaluating the stability index of the detected frequency source, and selecting a signal source with the same level or higher level than the detected frequency source as a compensation detection quantity source;

s4, frequency drift correction: and (3) assuming the daily stability and the magnitude of daily drift by using a rubidium atomic frequency standard, and correcting according to the daily stability and the magnitude of daily drift.

Further, in S2, the optical field test module adopts an optical pumping method to improve the signal-to-noise ratio of the passive rubidium atomic clock, and the energy level shift of pumping light to the passive rubidium atom is:

wherein P is a dipole moment operator; e is the complex amplitude of the time optical electric field, and gamma is the service life of the alpha excited state; e_αIs in an excited state; e_iEnergy in the ground state energy level.

Since only the b-line of the passive rubidium atom is pumped, the energy level shift of F1 and mF 0 is usually caused, and thus the optical frequency shift and the energy level shift have the following relationship:

2πhδf＝-δε

in addition, if the pumping light is monochromatic, and exactly ω ═ ω_αiNo optical frequency shift is caused; if ω > ω_αiThen a negative frequency shift is caused; if omega is less than omega_αiA positive frequency shift is caused; if ω and ω_αiIf the difference is far away, the absolute value of the frequency shift amount is caused to be equal to | omega-omega_αiL is in inverse proportion.

In an actual rubidium atomic clock, pumping light is not monochromatic light, but is superposition of a plurality of spectral lines with certain line width and line type functions, one part of frequency components in the range of the line type functions of the pumping light spectrum generate positive optical frequency shift, and the other part of frequency components generate negative optical frequency shift. The frequency shift of the 0-0 transition caused by the non-monochromatic light is the superposition of the frequency shifts caused by a plurality of monochromatic lights, so that for rubidium atomic clocks, the fact that the spectral line shape of the pumping light is kept unchanged is important for reducing the influence of the optical frequency shift on the aging drift of the frequency standard.

In addition, the rubidium atomic frequency standard in S4 adopts a spiral tube current mode, and a calculation formula of the magnitude of a magnetic field generated by the current is as follows:

wherein n is the number of turns per unit length of the coil; i is the electrifying current;is constant 10^-7。

Besides, the calculation formula of the number of turns per unit length of the coil is as follows:

wherein m is the number of turns of the magnetic field winding; r is the radius of the winding.

The foregoing shows and describes the general principles, essential features, and advantages of the invention. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, and the preferred embodiments of the present invention are described in the above embodiments and the description, and are not intended to limit the present invention. The scope of the invention is defined by the appended claims and equivalents thereof.