JP2018093271A - Atomic oscillator and method for controlling atomic oscillator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an atomic oscillator that has improved short-term frequency stability while the atomic oscillator is intermittently operated.SOLUTION: The present atomic oscillator is an atomic oscillator that adjusts an output frequency of a reference oscillator through intermittent feedback control using the resonance frequency of atoms and outputs the adjusted frequency, and comprises a control part that, on the basis of a frequency control value of the reference oscillator in a first period during which the atomic oscillator performs the feedback control, controls the output frequency of the reference oscillator in a second period during which the atomic oscillator stops the feedback control.SELECTED DRAWING: Figure 5

Description

  The present invention relates to an atomic oscillator and a method for controlling the atomic oscillator.

  There is an atomic clock (atomic oscillator) as a clock for measuring extremely accurate time, and a technique for downsizing the atomic oscillator has been studied. An atomic oscillator is an oscillator that controls the output frequency of a built-in reference oscillator based on the amount of transition energy of electrons constituting atoms such as alkali metals. In the state where there is no disturbance, a very precise value can be obtained, so that higher frequency stability can be obtained compared to a crystal oscillator or the like.

  Some conventional atomic oscillators perform intermittent operation to reduce power consumption and the like. In intermittent operation, the reference oscillator is operated autonomously without performing feedback control for a certain period of time, and feedback control based on atomic resonance is performed after the lapse of a certain period of time to correct frequency fluctuations caused by the autonomous operation of the reference oscillator. is there. For example, it is proposed that the control unit for controlling the frequency is configured in a digital configuration, and the timing for outputting the control signal is provided with a period during which the control signal is operating with a predetermined duty ratio or cycle and a period during which the control signal is stopped. (For example, refer to Patent Document 1).

  However, when performing intermittent operation, there is no feedback control from atomic resonance during the autonomous operation of the reference oscillator, so long-term frequency stability is almost the same as when intermittent operation is not performed. Stability is inferior.

  Further, when the atomic oscillator is used as a timepiece, the time lag is obtained by integrating the deviation of the output frequency of the atomic oscillator with respect to the reference frequency. Thus, when an intermittently operated atomic oscillator is used as a timepiece, the power consumption is low, but there is a problem that the time shift becomes large because of short-term frequency stability.

  The present invention has been made in view of the above, and an object of the present invention is to provide an atomic oscillator with improved short-term frequency stability in an intermittently operated state.

  The atomic oscillator is an atomic oscillator that adjusts the output frequency of the reference oscillator by intermittent feedback control using the resonance frequency of the atoms, and outputs the adjusted frequency. The atomic oscillator has a first period in which the feedback control is performed. It is a requirement to have a control unit that controls the output frequency of the reference oscillator in the second period in which the feedback control is stopped based on the frequency control value of the reference oscillator.

  According to the disclosed technique, an atomic oscillator having improved short-term frequency stability in an intermittently operated state can be provided.

1 is a schematic configuration diagram of an atomic oscillator according to a first embodiment. It is a block diagram which illustrates the hardware constitutions of a control part. It is a figure which illustrates the functional block of a control part. It is an example of the flowchart which shows operation | movement of the atomic oscillator which concerns on 1st Embodiment. It is a figure explaining the intermittent operation | movement of the atomic oscillator which concerns on 1st Embodiment. It is a figure explaining the intermittent operation | movement of the conventional atomic oscillator. It is an example of the flowchart which shows the operation | movement of the atomic oscillator which concerns on the modification of 1st Embodiment. It is a schematic block diagram of the atomic oscillator which concerns on 2nd Embodiment. It is an example of the flowchart which shows the operation | movement of the atomic oscillator which concerns on 2nd Embodiment.

  Hereinafter, embodiments for carrying out the invention will be described with reference to the drawings. In the drawings, the same components are denoted by the same reference numerals, and redundant description may be omitted.

<First Embodiment>
(Atomic oscillator)
FIG. 1 is a schematic configuration diagram of an atomic oscillator according to the first embodiment. Referring to FIG. 1, an atomic oscillator 1 is a CPT-type atomic oscillator that uses quantum interference effects (CPT (Coherent Population Trapping) resonance). However, the method is not limited to the CPT method, and other methods such as a double resonance method using resonance light and microwave may be used.

  The atomic oscillator 1 adjusts the output frequency of the reference oscillator by intermittent feedback control using the resonance frequency of the atom, and outputs the adjusted frequency. The feedback control is, for example, control for adjusting the output frequency of the reference oscillator or the frequency obtained by multiplying the output frequency of the reference oscillator so as to coincide with the resonance frequency of the atom.

  As shown in FIG. 1, the atomic oscillator 1 includes a semiconductor laser 10, a gas cell 20, a coil 30, a photodetector 40, detection circuits 50 and 60, a reference oscillator 70, a microwave synthesizer 80, a drive circuit 90, and a control unit 100. Have. The semiconductor laser 10, the gas cell 20, the coil 30, and the photodetector 40 constitute an atomic resonance unit. The atomic oscillator 1 generates a side band by frequency-modulating the semiconductor laser 10 and makes laser beams having two different wavelengths, which are the side bands, enter the gas cell 20. Thus, the modulation frequency is controlled by the light absorption characteristic due to the quantum interference effect by the two types of resonance light.

  The semiconductor laser 10 is a light source that irradiates the gas cell 20 with laser light. As the semiconductor laser 10, for example, a vertical cavity surface emitting laser (VCSEL) can be used.

The gas cell 20 is one in which alkali metal atoms such as rubidium (Rb) and cesium (Cs) are sealed in a container formed of glass or the like. Further, a buffer gas such as neon (Ne), argon (Ar), or nitrogen (N ₂ ) may be sealed in the container of the gas cell 20.

  The coil 30 applies a uniform magnetic field to the gas cell 20 to cause Zeeman splitting of alkali metal atoms enclosed in the gas cell 20.

  The light detector 40 detects light transmitted through the gas cell 20 from the laser light irradiated to the gas cell 20 by the semiconductor laser 10 and outputs a detection signal corresponding to the intensity of the light. The detection signal of the photodetector 40 is input to the detection circuits 50 and 60. As the photodetector 40, for example, a photodiode can be used.

  The detection circuits 50 and 60 are circuits for controlling the emission wavelength of the semiconductor laser 10 to a wavelength necessary for excitation of alkali metal atoms (center frequency f0).

  The reference oscillator 70 is an oscillator whose output frequency is adjusted according to the magnitude of the signal from the detection circuit 60. As the reference oscillator 70, a crystal oscillator such as a temperature compensated crystal oscillator (TCXO) can be used.

  An input signal at the control terminal of the reference oscillator 70 may be referred to as a frequency control value. The frequency control value is, for example, an analog voltage. In this case, the output frequency of the reference oscillator 70 changes according to the analog voltage applied to the control terminal. However, the input signal at the control terminal of the reference oscillator 70 is not limited to an analog voltage, and may be a digital signal. In this case, by transmitting a command to the control terminal of the reference oscillator 70, the output frequency of the reference oscillator 70 changes.

  The microwave synthesizer 80 generates a microwave (frequency fm) using the output (for example, 10 MHz) of the reference oscillator 70 as a reference. By superimposing this microwave on the drive circuit 90 of the semiconductor laser 10, light of f0 ± fm, f0 ± 2fm,... Is generated in addition to light of the center frequency f0. When light of f0 ± fm is used as a resonant light pair for causing the CPT phenomenon, fm matches with a half of the frequency (resonance frequency) corresponding to the energy difference between the two ground levels of the alkali metal atom. Is feedback controlled.

  For example, when Cs is used as the alkali metal atom, the resonance frequency is 9.192631770 GHz, so that the microwave output frequency fm is controlled to be 4.596331585 GHz. That is, the output frequency of the reference oscillator 70 serving as a microwave reference is feedback-controlled.

  The control unit 100 is a part that controls the operation of the entire atomic oscillator 1. FIG. 2 is a block diagram illustrating a hardware configuration of the control unit. Referring to FIG. 2, the control unit 100 includes a CPU 101 (Central Processing Unit), a ROM 102 (Read Only Memory), a RAM 103 (Random Access Memory), an I / F 104 (Interface), and a bus line 105. doing. The CPU 101, ROM 102, RAM 103, and I / F 104 are connected to each other via a bus line 105. In addition, the control part 100 can be provided with other devices, such as FPGA (Field Programmable Gate Array) and a non-volatile memory as needed.

  The CPU 101 controls each function of the control unit 100. A ROM 102 serving as a storage unit stores a program executed by the CPU 101 to control each function of the control unit 100 and various types of information. A RAM 103 as storage means is used as a work area of the CPU 101. The RAM 103 can temporarily store predetermined information.

  The I / F 104 is an interface for connecting to other devices and the like, and is provided as necessary. The I / F 104 can be connected to an external input device (keyboard or the like), an external network, an external storage device (hard disk, semiconductor memory, CD-ROM, DVD, or the like). A program or the like executed to control each function may be provided via the I / F 104 from an external network or an external storage device.

  FIG. 3 is a diagram illustrating a functional block of the control unit. Referring to FIG. 3, the control unit 100 includes a flag detection unit 111, a control unit 112, and a fitting unit 113. Specific functions of each functional block will be described later.

(Operation of atomic oscillator)
FIG. 4 is an example of a flowchart showing the operation of the atomic oscillator according to the first embodiment. Here, it is assumed that the power source of the atomic oscillator 1 is turned on and the operation of the atomic oscillator 1 is started.

  As shown in FIG. 4, first, in step S201, the flag detection unit 111 of the control unit 100 determines whether or not the intermittent operation flag is off. The intermittent operation flag is a flag that is turned on when the reference oscillator 70 built in the atomic oscillator 1 is operating autonomously, and is turned off when the atomic oscillator 1 is feedback-controlled by the resonance frequency.

  If it is determined in step S201 that the intermittent operation flag is off (in the case of YES), the process proceeds to step S202. In step S202, the control unit 112 of the control unit 100 operates the atomic resonance unit, the microwave synthesizer 80, and the like, and feedback-controls the reference oscillator 70 based on the resonance frequency.

  Next, in step S203, the fitting means 113 of the control unit 100 causes the frequency control value of the reference oscillator 70, the temperature of the gas cell 20, the amount of light irradiated to the gas cell 20, the output level of the microwave generated by the microwave synthesizer 80, and the like. Is stored as data. For example, the fitting unit 113 can store these data in the RAM 103 every predetermined time, and can read out the data from the RAM 103 when necessary.

  For the temperature of the gas cell 20, the amount of light irradiated to the gas cell 20, the output level of the microwave, etc., data that is normally monitored by the control means 112 of the control unit 100 for stabilizing the resonance frequency can be used. .

  Next, in step S204, the fitting means 113 of the control unit 100 calculates an approximate expression of the frequency control value of the reference oscillator 70 for correcting the time change based on the data accumulated in step S203. That is, the fitting unit 113 calculates a coefficient and a constant term by fitting a frequency control value when the atomic oscillator 1 is feedback controlled to a desired function.

  The approximate expression can be calculated using, for example, a known least square method. Since the interval of the intermittent operation is, for example, about 1 hour to 1 day, the frequency control value can be approximated by a quadratic function or a logarithmic function. After executing step S204, the process proceeds to step S201.

  If it is determined in step S201 that the intermittent operation flag is on (in the case of NO), the process proceeds to step S205. In step S205, the control unit 112 of the control unit 100 stops the operation of the atomic resonance unit, the microwave synthesizer 80, and the like (does not perform feedback control using the resonance frequency). Then, the control unit 112 performs frequency control of the reference oscillator 70 based on the approximate expression calculated in step S204 according to the elapsed time.

  Thereafter, the operations in steps S201 to S205 are repeated. As described above, the operation of the atomic oscillator 1 is executed. Note that the operation of the atomic oscillator 1 by the control unit 100 may be repeated as long as the power of the atomic oscillator 1 is turned on, or may be repeated as long as a predetermined condition is satisfied.

  The timing for switching on / off of the intermittent operation flag is not particularly limited, but may be controlled so as to be switched at a constant cycle, or may be controlled so as to be switched at an arbitrary timing.

  Next, the difference between the operation of the atomic oscillator 1 and the operation of the conventional atomic oscillator will be described with reference to FIGS. FIG. 5 is a diagram illustrating the intermittent operation of the atomic oscillator according to the first embodiment. FIG. 6 is a diagram for explaining the intermittent operation of a conventional atomic oscillator.

  As described above, in the atomic oscillator 1, an approximate expression is calculated based on, for example, a time change of the frequency control value of the reference oscillator 70 in which the intermittent operation flag is off, and the reference is based on the approximate expression while the intermittent operation flag is on. The frequency of the oscillator 70 is controlled.

  As a result, as shown in FIG. 5, when the intermittent operation flag is switched from OFF to ON, or when the intermittent operation flag is switched from ON to OFF, the frequency control value of the reference oscillator 70 does not change stepwise but continuously changes. The output frequency (solid line) of the oscillator 1 matches the reference frequency (broken line) with high accuracy.

  On the other hand, in the conventional atomic oscillator shown in FIG. 6, when the intermittent operation flag is on, the autonomous operation of the reference oscillator without feedback control from the atomic resonance by stopping the operation of the atomic resonance unit, the microwave synthesizer, etc. It becomes.

  For this reason, when the intermittent operation flag is on, the power consumption is low, but the frequency control value of the reference oscillator is constant, and the output frequency of the atomic oscillator becomes unstable. For example, as shown in FIG. 6, the output frequency (solid line) of the atomic oscillator decreases with time, and the deviation of the output frequency of the atomic oscillator with respect to the reference frequency (broken line) increases.

  Therefore, in the case of intermittent operation, when it is considered in terms of frequency, it is stable in the long term, but unstable in the short term. In particular, when an atomic oscillator is used as a clock, the time lag is an integrated value of the frequency lag from the reference frequency, and therefore the time lag becomes large even in the long run. In FIG. 6, the sum of the hatched portions surrounded by the solid line and the broken line is the time lag when the atomic oscillator is used as a clock.

  As is clear from comparison between FIG. 5 and FIG. 6, the atomic oscillator 1 can improve short-term frequency stability in the intermittent operation state as compared with the conventional atomic oscillator. For example, when the atomic oscillator 1 is used as a timepiece, the time lag can be reduced.

  As described above, in the atomic oscillator 1, the approximate expression is calculated based on the frequency control value or the like of the reference oscillator while the intermittent operation flag is off (first period during which feedback control is performed), and the intermittent operation flag is calculated based on the approximate expression. Is controlled (the second period during which feedback control is stopped) to control the output frequency of the reference oscillator 70.

  Thereby, the short-term frequency stability in the state which operated the atomic oscillator 1 intermittently can be improved. As the time during which the feedback operation is performed as the atomic oscillator 1 becomes longer, the accuracy of the approximate expression is improved, and improvement in frequency stability can be expected.

  Note that only the time change of the frequency control value of the reference oscillator 70 in which the intermittent operation flag is OFF in step S203 may be accumulated, and the approximate expression may be calculated based on only the time change of the frequency control value in step S204.

  However, even when the atomic oscillator 1 is performing a feedback operation, the resonance frequency changes due to factors such as changes in the temperature and light quantity of the gas cell 20 and changes in the output level of the microwave. It can happen that it falls.

  For this reason, fitting is not performed using only the frequency control value, but a variety of parameters (temperature change and light quantity change of the gas cell 20) that cause the resonance frequency grasped by the control unit 100 together with the frequency control value. It is desirable to perform fitting in consideration of a change in the output level of the microwave.

  That is, by subtracting the contribution due to the change of various parameters from the change of the frequency control value, it is possible to correctly fit the change with time of the frequency control value of the reference oscillator 70. The influence of various parameters on frequency changes can be grasped to some extent in advance, and individual differences can be eliminated by learning during operation.

  By the way, a method of controlling the frequency during the autonomous operation of the reference oscillator based on a predetermined approximate expression is also conceivable. However, the coefficients and constant terms of the approximated function differ depending on the individual difference of the reference oscillator and the operating environment. Therefore, in the method using the approximate expression determined in advance, a significant improvement in frequency stability cannot be expected, and conversely, it may be deteriorated. In the control method according to the present embodiment, by accumulating and learning information obtained during operation, the influence of individual differences of the reference oscillator and the operating environment is eliminated, and the accuracy of the approximate expression is improved each time. It is possible to go.

<Modification of First Embodiment>
In the modification of the first embodiment, an example in which an approximate expression is calculated by a method different from that of the first embodiment is shown. In the modification of the first embodiment, the description of the same components as those of the already described embodiments may be omitted.

  FIG. 7 is an example of a flowchart showing the operation of the atomic oscillator according to the modification of the first embodiment. In FIG. 7, step S203 of FIG. 4 is replaced with steps S206 and S207.

  In FIG. 7, when it is determined in step S201 that the intermittent operation flag is OFF (in the case of YES), the process proceeds to step S202, and the control means 112 of the control unit 100 performs feedback control. Next, in step S206, the control means 112 of the control unit 100 determines whether or not a fixed time has elapsed after switching the intermittent operation flag.

  If it is determined in step S206 that a certain time has elapsed (in the case of YES), the process proceeds to step S201. If it is determined in step S206 that the predetermined time has not elapsed (NO), the process proceeds to step S207.

  In step S207, the fitting means 113 of the control unit 100 accumulates the change in the frequency control value of the reference oscillator 70 as data. That is, the change in the frequency control value of the reference oscillator 70 from immediately after the intermittent operation flag is switched from on to off until a predetermined time elapses is stored as data.

  Next, in step S204, the fitting means 113 of the control unit 100 calculates an approximate expression of the frequency control value of the reference oscillator 70 for correcting the time change based on the data accumulated in step S207. That is, the fitting means 113 accumulates and learns the time change of the frequency control value of the reference oscillator 70 from when the intermittent operation flag is switched from on to off until a certain time elapses, thereby learning a desired function. To calculate coefficients and constant terms.

  Other processes are the same as those in the flowchart shown in FIG. In the method shown in FIG. 7, although the accuracy of the approximate expression is inferior to that of the method shown in FIG. Therefore, this is an effective means when the memory amount of the control unit 100 is small.

  Note that in the control method according to the first embodiment and the modified example of the first embodiment, the control unit 100 needs to be operated even when the intermittent operation flag is on, so that the power consumption increases slightly. There are concerns. However, since the time required for control is considerably short (for example, several ms) with respect to the frequency control interval (for example, 1 s), power consumption can be reduced by stopping the operation of the control unit 100 during the non-control time. Can be further lowered.

<Second Embodiment>
In the second embodiment, an example of a control method using temperature sensor data (environment temperature) will be described. In the second embodiment, description of the same components as those of the already described embodiments may be omitted.

  FIG. 8 is a schematic configuration diagram of an atomic oscillator according to the second embodiment. Referring to FIG. 8, the atomic oscillator 2 is different from the atomic oscillator 1 (see FIG. 1) in that a temperature sensor 150 that detects an environmental temperature (outside temperature of the atomic oscillator 2) is added. The environmental temperature detected by the temperature sensor 150 is input to the control unit 100.

  FIG. 9 is an example of a flowchart showing the operation of the atomic oscillator according to the second embodiment. In FIG. 9, steps S208 to S210 are provided instead of steps S203 to S205 in FIG.

  First, step S201 is executed in the same manner as in FIG. 4, and if it is determined in step S201 that the intermittent operation flag is OFF (in the case of YES), step S202 is executed in the same manner as in FIG. .

  Next, in step S208, the fitting means 113 of the control unit 100 determines the frequency control value of the reference oscillator 70, the temperature of the gas cell 20, the amount of light irradiated to the gas cell 20, the output level of the microwave generated by the microwave synthesizer 80, Changes such as environmental temperature detected by the temperature sensor 150 are accumulated as data. For example, the fitting unit 113 can store these data in the RAM 103 every predetermined time, and can read out the data from the RAM 103 when necessary.

  Next, in step S209, the fitting means 113 of the control unit 100 calculates an approximate expression of the frequency control value of the reference oscillator 70 for correcting the environmental temperature change and the temporal change based on the data accumulated in step S208. To do. When it is determined in step S201 that the intermittent operation flag is on (in the case of NO), in step S210, the control unit 112 of the control unit 100 stops the feedback control, and according to the environmental temperature and the elapsed time. The frequency control of the reference oscillator 70 is performed based on the approximate expression calculated in step S209.

  That is, by observing a change in the environmental temperature with the temperature sensor 150, not only a change over time of the frequency control of the reference oscillator 70 but also a temperature characteristic is modeled during the intermittent operation, and the autonomous operation of the reference oscillator 70 according to the change in the environmental temperature. Perform frequency control during. Thereby, the frequency stability can be further improved.

  The change in the output frequency of the reference oscillator 70 is largely due to the temperature change in addition to the change with time. Therefore, when the environmental temperature changes during the autonomous operation of the reference oscillator 70, the effect of improving the frequency stability is diminished only by the control based on the model of change with time.

  Further, when the power consumption change when the atomic oscillator is intermittently operated is large, the temperature of the reference oscillator 70 inside the atomic oscillator is likely to change even if the environmental temperature does not change. Therefore, in order to improve frequency stability, frequency control according to temperature change is required.

  Such temperature characteristics, like changes with time, have large individual differences, so modeling is required for each individual. Regarding the modeling of temperature characteristics, the change in the frequency control value when the intermittent operation flag is off, that is, when operating as an atomic oscillator, and the change in the environmental temperature observed by the temperature sensor are made to correspond to the change over time. However, the coefficient may be determined.

  By using a large number of data, it is possible to model changes over time and temperature characteristics, respectively. In addition, data at the time of shipping inspection or when it was started before may be stored, and an approximate expression may be calculated based on the data. In this case, highly accurate fitting is possible in a short time.

  Note that it is desirable that the temperature sensor is disposed in the immediate vicinity of the reference oscillator and the temperature change of the reference oscillator is observed. It is also possible to more accurately capture the temperature change of the reference oscillator by arranging a plurality of temperature sensors and observing the temperature distribution.

  The preferred embodiment has been described in detail above. However, the present invention is not limited to the above-described embodiment, and various modifications and replacements are made to the above-described embodiment without departing from the scope described in the claims. Can be added.

  For example, in the modification of the first embodiment, the temperature sensor 150 is provided, and the change in the frequency control value of the reference oscillator 70 from the time immediately after the intermittent operation flag is switched from on to off until a certain time elapses, An approximate expression may be calculated based on the data of the change in environmental temperature from when the intermittent operation flag is switched from on to off until a predetermined time elapses.

  Further, in the modification of the first embodiment, the approximate expression may be calculated in consideration of various parameters that cause the resonance frequency grasped by the control unit 100 together with the frequency control value. .

DESCRIPTION OF SYMBOLS 1, 2 Atomic oscillator 10 Semiconductor laser 20 Gas cell 30 Coil 40 Photo detector 50, 60 Detection circuit 70 Reference oscillator 80 Microwave synthesizer 90 Drive circuit 100 Control part 101 CPU
102 ROM
103 RAM
104 I / F
105 Bus line 111 Flag detection means 112 Control means 113 Fitting means 150 Temperature sensor

Patent No. 5402036

Claims (10)

An atomic oscillator that adjusts the output frequency of the reference oscillator by intermittent feedback control using the resonance frequency of the atom and outputs the adjusted frequency,
And a control unit configured to control an output frequency of the reference oscillator in a second period in which the feedback control is stopped based on a frequency control value of the reference oscillator in a first period in which the feedback control is performed. Atomic oscillator.   The control unit calculates an approximate expression based on a time change of the frequency control value of the reference oscillator in the first period, and controls the output frequency of the reference oscillator in the second period based on the approximate expression. 2. The atomic oscillator according to claim 1, wherein   3. The atomic oscillator according to claim 2, wherein the control unit calculates the approximate expression based on a time change of a frequency control value of the reference oscillator for the entire first period.   The control unit calculates the approximate expression based on a time change of a frequency control value of the reference oscillator from when the second period is switched to the first period until a predetermined time elapses. The atomic oscillator according to claim 2. It has a temperature sensor that detects the ambient temperature,
The control unit controls an output frequency of the reference oscillator in the second period based on a frequency control value of the reference oscillator in the first period and the environmental temperature in the first period. 2. The atomic oscillator according to claim 1.   The control unit calculates an approximate expression based on a time change of the frequency control value of the reference oscillator in the first period and a time change of the environmental temperature in the first period, and based on the approximate expression, 6. The atomic oscillator according to claim 5, wherein an output frequency of the reference oscillator in a second period is controlled.   The control unit calculates the approximate expression based on a time change of a frequency control value of the reference oscillator for the entire first period and a time change of the environmental temperature for the entire first period. The atomic oscillator according to claim 6.   The control unit switches from the second period to the first period and changes from time to time of the frequency control value of the reference oscillator until a predetermined time elapses, and switches from the second period to the first period. The atomic oscillator according to claim 6, wherein the approximate expression is calculated on the basis of a temporal change in the environmental temperature until a predetermined time elapses.   The control unit controls an output frequency of the reference oscillator in the second period in consideration of a parameter that causes a change in the resonance frequency together with a frequency control value of the reference oscillator. Item 9. The atomic oscillator according to any one of Items 1 to 8. An atomic oscillator control method for adjusting an output frequency of a reference oscillator by intermittent feedback control using an atomic resonance frequency and outputting an adjusted frequency,
Controlling an output frequency of the reference oscillator in a second period of stopping the feedback control based on a frequency control value of the reference oscillator in a first period of performing the feedback control Method.

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