JPH0998086A - Gas cell type atomic oscillator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a gas cell type atomic oscillator where degradation in stability of the frequency due to the variance of the air pressure is suppressed. SOLUTION: The frequency of a standard frequency signal generated in a frequency signal generation part 3 by utilizing the light and microwave double resonance in a double resonance part 2 of the microwave, which is generated in a microwave generation circuit 4 based on the standard frequency signal generated by the frequency signal generation part 3, and exciting light from an exciting light source part 1 is stabilized. At this time, air pressure is measured by an air pressure measurer 6, and a correction signal corresponding to the measured value is sent from a correction signal generation circuit 7 to a controller 8, and the controller 8 controls at least one of a current supply device 5 and the microwave generation circuit 4 based on the correction signal to suppress the variance of the frequency due to the variance of air pressure.

Description

Detailed Description of the Invention

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas cell type atomic oscillator which is compact and has a simple structure, but can obtain high frequency stability, and more particularly, it suppresses fluctuations in resonance frequency due to fluctuations in atmospheric pressure to stabilize frequency. The present invention relates to a gas cell type atomic oscillator having a higher degree.

[0002]

2. Description of the Related Art A gas cell type atomic oscillator is an oscillator having a very high stability which stabilizes an oscillation frequency with a resonance frequency peculiar to an atom as a frequency reference. Currently in practical use is, for example, a gas cell type rubidium atomic oscillator that uses rubidium as atoms to be enclosed in a gas cell, and is used as a secondary frequency standard for communication, broadcasting, navigation, G
It is used in various fields such as PS satellites.

FIG. 9 is a basic configuration diagram of a conventional gas cell type atomic oscillator. A conventional technique will be described with reference to FIG. The conventional gas cell type atomic oscillator includes an excitation light source unit 1, a double resonance unit 2, a current supply device 5, a signal processing control device 31, a voltage control crystal oscillator 32, and a frequency synthesis / multiplication circuit 4. The excitation light source unit 1 outputs excitation light.

The double resonance section 2 will be described with reference to the configuration diagram shown in FIG. The double resonance part 2 includes a gas cell 21.
A microwave cavity resonator 22 having a built-in capacitor, a static magnetic field coil 27 for generating a stable DC parallel magnetic field over the entire length of the gas cell 21, and a constant temperature heater 2 for heating and constant temperature outside thereof.
6 and a plurality of magnetic shield tanks 2 for removing fluctuations in the external magnetic field
And 5. The microwave cavity resonator 22 located at the center of the double resonance part 2 includes a gas cell 21 in which an alkali metal atom is enclosed, an excitation light input window 28 for introducing excitation light, and a gas cell at a position opposite to the excitation light input window 28. It is provided with a photoelectric conversion element 23 that receives the light transmitted through 21 and converts the light intensity into an electric signal intensity and outputs it, and a microwave excitation antenna 24. In addition, the normal gas cell 2
In order to narrow the resonance spectrum width of double resonance within 1,
An inert gas is filled as a buffer gas together with the alkali metal atoms.

The current supply device 5 is a coil 2 of the double resonance part 2.
Supply a constant current to 7. The current value is set inside the current supply device 5. The signal processing control device 31 receives a signal from the double resonance unit 2 and outputs a control signal corresponding to the signal. The voltage controlled crystal oscillator 32 outputs a standard frequency signal (frequency f1). The frequency synthesis / multiplication circuit 4 synthesizes and multiplies frequencies based on the standard frequency signal, and outputs a microwave. The frequency of the microwave is determined by the setting of the switch in the frequency synthesis / multiplication circuit 4.

The operation of the conventional gas cell type atomic oscillator configured as described above will be described. Voltage controlled crystal oscillator 32
The output f1 of the above is synthesized and multiplied by the frequency synthesis / multiplication circuit 4 to generate a microwave frequency N × f1 close to the resonance frequency f2 of the atoms enclosed in the gas cell 21. The double resonance section 2 is excited at this microwave frequency, and the excitation light source section 1 irradiates the double resonance section 2 with excitation light to cause a double resonance phenomenon described later. The double resonance section 2 outputs a signal containing information on the frequency difference (N.times.f1 -f2) between the applied microwave frequency and the resonance frequency. The signal processing controller 31 extracts frequency information from the signal and controls the oscillation frequency of the voltage controlled crystal oscillator 32 so that the frequency difference becomes zero. The output frequency f1 of the voltage controlled crystal oscillator 32 is taken out as a standard frequency output and used.

Here, the optical / microwave double resonance phenomenon will be described by taking the three-level atomic system model of the energy level of the rubidium atom shown in FIG. 11 as an example. In FIG. 11, the rubidium atoms in the thermal equilibrium state are equally distributed in two hyperfine levels (F = 1, F = 2) of the ground level (5S1 / 2) [FIG. 11 (a)]. . At this time, when the rubidium atom is irradiated with resonance light (excitation light) having a certain constant wavelength, the hyperfine level with a high ground level (5S1 / 2, F = 2)
The rubidium atom at is not changed, but the rubidium atom at the lower hyperfine level (5S1 / 2, F = 1) absorbs the optical energy of the excitation light and emits light at the excitation level (5P3 / 2). Pumped. The rubidium atom pumped to the excitation level (5P3 / 2) spontaneously emits energy, and two hyperfine levels (F = F = S) of the ground level (5S1 / 2) are emitted.
1, F = 2) with equal probability. This process is repeated by continuing to irradiate excitation light, and most of rubidium atoms have hyperfine levels with high ground levels (5S1 / 2, F =
2), and the state of population inversion appears [Fig. 11
(B)]. When a high-frequency magnetic field (microwave) close to the resonance frequency of the rubidium atom is applied in this state, energy is emitted upon receipt of resonance vibration, and the hyperfine level (5S1 / 2, F = 1) with a low ground level is released. Stimulated emission [Fig. 11
(C)]. The low-level atoms are optically pumped to the excitation levels again by the excitation light, but when the microwave high-frequency magnetic field deviates from the resonance frequency, the number of stimulated emission atoms decreases, and as a result, the low-level atoms decrease. (5S1 / 2, F =
The number of atoms in 1) is reduced, and as a result, the number of atoms optically pumped is reduced, and the absorption amount of excitation light is reduced. Therefore, by observing the level of light transmitted through the gas cell (transmitted light) with a photoelectric conversion element and controlling the microwave frequency so that the level of transmitted light is always minimum (that is, absorption of excitation light is maximum), It is possible to obtain a standard frequency obtained by transferring an extremely stable frequency having a natural resonance frequency.

In recent years, a semiconductor laser (Laser Diode: hereinafter referred to as LD) has been put into practical use due to the progress of semiconductor technology, and has come to be used as an excitation light source of a gas cell type atomic oscillator. Before using the LD, a conventional excitation light source uses a lamp excitation method in which a lamp cell in which atoms are enclosed together with a carrier gas is excited by high frequency to discharge, and discharge light having a wide spectrum including a desired wavelength is used as excitation light. Was there. The LD can precisely control the oscillation wavelength by controlling the operating (injection) current and operating temperature, and can obtain highly coherent excitation light with a single spectrum, which enables highly efficient atom pumping. The frequency stability was improved by an order of magnitude compared to the lamp excitation method.

Therefore, in the lamp excitation system, since the factors on the excitation light source side are large, if the temperature is controlled to be constant by using the constant temperature heater 26 for heating and constant temperature, there is no problem in the overall performance. The influence of pressure shift, in which the resonance frequency of atoms changes due to fluctuations in the internal pressure of the gas cell 21, has become apparent. For the internal pressure fluctuation of the gas cell 21 caused by the temperature fluctuation, further precise and highly stable temperature control of the microwave cavity resonator 22 including the gas cell 21 and a plurality of buffer gases enclosed together with the metal gas. The resonance frequency is stabilized by adjusting the type and pressure of each type. Up to this point is the conventional technique.

[0010]

However, it has been found that the resonance frequency still fluctuates even if the temperature control is made more precise and highly stable. The inventors investigated the relationship between the fluctuation of the temperature, the humidity and the atmospheric pressure of the room in which the gas cell type atomic oscillator is placed and the fluctuation of the resonance frequency in the examination of the factors of the pressure shift. In the survey, we recorded the output frequency data of the oscillator and the ambient temperature data of ambient temperature, atmospheric pressure and humidity in the measurement room, and performed a multiple regression analysis of the frequency data and ambient environmental factors. It was decided to seek and evaluate.

The data is automatically measured by a personal computer in order to eliminate reading errors, and the time interval is 10
Data was recorded every 0 seconds and long-term measurement was performed for about one and a half months. The fluctuation of the output frequency of the oscillator was measured by the phase comparison method with a certain reference value, and the hydrogen maser atomic oscillator was used as the frequency reference. The frequency stability performance of the hydrogen maser atomic oscillator is given by τ ≤ on the scale of Alan dispersion in which the two-sample dispersion is defined as the frequency stability scale in the time domain.
At (10 4) sec, σ y (τ) = 3 × (10 -13) / τ + 4 × (10 -14) /
√ (τ) + 8.5 × (10 to the 16th power), or (10 to the 4th power) <τ ≦ (10 to the 5th power) sec, σy
(Τ) ≦ 3.5 × (10 −15), which is sufficient performance as a frequency reference.

As a result of the multiple regression analysis, the correlation coefficient between the output frequency and the atmospheric pressure is as large as about 0.8, the correlation coefficient with the humidity is 0.2 or less, and the correlation with the temperature is about 0.3. , The possibility of the above-mentioned frequency stability deterioration due to the influence of atmospheric pressure has increased. Resonance frequency change for atmospheric pressure change is +1 mH
It was less than z / hPa. Therefore, we decided to investigate further by focusing on the relationship between the output frequency and atmospheric pressure, using a simple vacuum tank, arranging the double resonance part in the tank, and depressurizing the tank by 10 hPa by the rotary pump. When the atmospheric pressure data and the output frequency data of the gas cell type atomic oscillator were recorded and the correlation was investigated, the rate of change and the directionality were in agreement with the long-term data.

Next, considering where in the double resonance portion the atmospheric pressure fluctuation affects, the gas cell is most effective at a place where the mechanical strength is weak, and when the gas cell is distorted by the influence of the atmospheric pressure. As a result of simulating the amount of change in cell volume and the amount of change in frequency resulting therefrom, the rate of change was in agreement with the above-mentioned measurement result. In particular, it was found that when both end surfaces were flat and cylindrical, the center of the flat plate was bent and the joint between the flat plate and the cylinder was distorted.

From the above, the gas cell in the double resonance portion is distorted due to the change of atmospheric pressure, the internal pressure of the gas cell is changed, and the pressure shift of the buffer gas is generated, so that the resonance frequency may be changed. confirmed. An object of the present invention is to solve the above-mentioned problems and to provide a gas cell type atomic oscillator in which deterioration of frequency stability due to fluctuation of atmospheric pressure is suppressed.

[0015]

Means for Solving the Problems The internal pressure of the gas cell fluctuates due to atmospheric pressure fluctuation, and as a result, the resonance frequency fluctuates, but the fluctuation amount can be confirmed experimentally. Therefore, the gas cell type atomic oscillator of the present invention is provided with an atmospheric pressure measuring device that measures the pressure of the outside air (atmospheric pressure outside the gas cell), and corrects the resonance frequency fluctuation amount based on the measurement value of the atmospheric pressure measuring device. And

That is, a double resonance part containing a gas cell containing alkali metal atoms and a coil for generating a magnetic field in the gas cell, a current supply device for the coil, and generating excitation light for the alkali metal atoms. An excitation light source unit, a frequency signal generation unit that receives an output signal from the double resonance unit and generates a frequency signal corresponding to the output signal, and a resonance microwave of the alkali metal atom that receives the frequency signal. In a gas cell type atomic oscillator having a microwave generation circuit, the excitation light source unit is a semiconductor laser, further, measuring the atmospheric pressure around the gas cell,
An atmospheric pressure measuring device which outputs a signal corresponding to the atmospheric pressure value, a correction signal generating circuit which receives a signal output from the atmospheric pressure measuring device and outputs a correction signal corresponding to the measured atmospheric pressure value,
A control device that receives the correction signal and controls at least one of the current of the coil and the frequency of the resonant microwave. At least one of the current supply device and the microwave generation circuit can be controlled by the control device.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 2 shows a first embodiment of the present invention.
Shown in The gas cell type atomic oscillator of the first embodiment is
A gas cell 21 in which alkali metal atoms are enclosed, a double resonance part 2 having a coil 27 for generating a magnetic field in the gas cell 21, and a current supply device 5 for the coil 27,
A pumping light source unit 1 made of a semiconductor laser for generating pumping light of the alkali metal atom, and a frequency signal generating unit 3 for receiving an output signal from the double resonance unit 2 and generating a frequency signal according to the output signal (signal A process control device 31 + a voltage controlled crystal oscillator 32), a microwave generation circuit (frequency synthesis / multiplication circuit) 4 for generating the resonance microwave of the alkali metal atom in response to the frequency signal, and an atmospheric pressure around the gas cell. An atmospheric pressure measuring device 6 that measures and outputs a signal corresponding to the atmospheric pressure value, and a correction signal generation circuit that receives a signal output from the atmospheric pressure measuring device 6 and outputs a correction signal corresponding to the measured atmospheric pressure value 7 and a control device 8 for controlling the frequency of the resonance microwave by receiving the correction signal, and the microwave generation circuit (frequency synthesis / multiplication circuit)
The multiplication factor in 4 can be changed by a signal from the outside. Microwave generator (frequency synthesis,
The multiplier circuit 4 has, for example, a configuration as shown in FIG. 3, and conventionally, M1 and M2 of the variable frequency dividers 41 and 42 in the figure are used after being set to a predetermined value by a dip switch or the like. In the first embodiment of the present invention, the M1,
M2 is set by "1" and "0" signals from the CPU of the controller 8 instead of the "1" and "0" signals generated by turning on and off the dip switch.

In the gas cell type atomic oscillator according to the first embodiment, the alkali metal atoms are irradiated with the resonance light and the resonance microwave to cause optical / microwave double resonance, and the resonance generated at that time is generated. The frequency of the standard frequency signal is controlled and output based on the frequency, which is the same as the conventional method, but the atmospheric pressure is measured by the atmospheric pressure measuring instrument, and the correction signal corresponding to the measured value is sent from the correction signal generating circuit to the control device. The control device controls the microwave generation circuit based on the correction signal so that the fluctuation of atmospheric pressure does not influence the frequency control. Under the control of the control device, the microwave generation circuit applies the microwave (frequency n2.f1) corrected to the microwave frequency n1.f1 based on the standard frequency signal (frequency f1) to the frequency .DELTA.f based on the correction signal. Send to the double resonance section. The relationship between the measured value of atmospheric pressure and the frequency .DELTA.f is obtained in advance, and the value of n2 for correcting n1.f1 by .DELTA.f is also obtained in advance. In the gas cell of the double resonance part, the gas cell is deformed by the change of the external atmospheric pressure, the internal volume of the gas cell is changed, the internal pressure of the gas cell is changed, and the resonance frequency is changed as a result. Since the change corresponds to the frequency .DELTA.f, the standard frequency signal is stabilized at the frequency f1 even though the resonance frequency changes from n1.f1 to n2.f1. That is, the fluctuation of the atmospheric pressure does not affect the frequency f1 of the standard frequency signal.

Next, FIG. 4 shows a second embodiment of the present invention. The gas cell type atomic oscillator of the second embodiment includes a gas cell 21 in which an alkali metal atom is enclosed and a double resonance part 2 having a coil 27 for generating a magnetic field in the gas cell 21, and a current supply for the coil 27. A device 5, an excitation light source unit 1 which is composed of a semiconductor laser and generates excitation light of the alkali metal atoms, and a frequency signal generator which receives an output signal from the double resonance unit 2 and generates a frequency signal corresponding to the output signal. Part 3 (signal processing control device 31 + voltage control crystal oscillator 32), microwave generation circuit (frequency synthesis / multiplication circuit) 4 for receiving the frequency signal and generating the resonance microwave of the alkali metal atom, and the gas cell An atmospheric pressure measuring device 6 that measures the atmospheric pressure around it and outputs a signal corresponding to the atmospheric pressure value, and a signal output from the atmospheric pressure measuring device 6 are received to obtain the measured atmospheric pressure value. A correction signal generating circuit 7 for outputting a response to the correction signal, the coil 2 receives the correction signal
A controller 8 for controlling the current for 7 and,
The current supplied by the current supply device 5 can be changed by a signal from the outside. The current supply device 5 has conventionally been controlled to supply a constant current so that the strength of the magnetic field by the coil 27 does not change, but in the second embodiment of the present invention, the control device 8 is used. Is supplied to the coil 27 of the double resonance part 2 in addition to the constant current supplied according to the correction signal.

In the gas cell type atomic oscillator of the second embodiment, the alkali metal atoms are irradiated with the resonance light and the resonance microwave to cause optical / microwave double resonance, and the resonance generated at that time is generated. Although the frequency of the standard frequency signal is controlled and output based on the frequency as in the conventional case, the atmospheric pressure is measured by the atmospheric pressure measuring device 6, and the correction signal corresponding to the measured value is controlled from the correction signal generating circuit 7. A current for correction based on the correction signal is sent to the device 8 and is supplied from the control device 8 to the current supply device 5 so that fluctuations in atmospheric pressure do not affect the frequency control. The current supply device 5 supplies to the coil 27 of the double resonance part 2 a current having a current value obtained by adding the current value Δi based on the correction signal to the current value supplied at the standard atmospheric pressure value. The relationship between the measured value of atmospheric pressure and the current value Δi is obtained in advance. As described above, the resonance frequency changes due to the change in the external atmospheric pressure. The change in the resonance frequency is due to the correction of the current value supplied to the coil 27 and the change in the strength of the DC parallel magnetic field. It is canceled and there is no change in the resonance frequency as a result. Therefore, the fluctuation of the atmospheric pressure does not affect the frequency f1 of the standard frequency signal.

[0021]

Embodiments of the present invention will be described below with reference to the drawings. Here, correction for changes in atmospheric pressure, which is the point of the present invention, will be described. The operation and the like of the portion that is not related to the correction are the same as those of the related art, and have been described in the section of the embodiment of the invention, and therefore will be omitted. FIG. 5 is a configuration diagram illustrating an example of the first embodiment. The atmospheric pressure around the double resonance part 2 is measured by the atmospheric pressure measuring device 6, and when the atmospheric pressure fluctuates, the fluctuation amount is output as a voltage value ΔV. In response to this, the frequency fluctuation amount correction circuit 9 which also functions as the correction signal generation circuit 7 and the control device 8 is processed by the analog / digital converter (A / D converter) 91.
Is converted into a digital signal by the CPU 92, and the frequency synthesis / multiplication is performed so that the microwave of the frequency corrected by the CPU 92 for the variation Δf of the resonance frequency corresponding to the voltage value ΔV is output from the frequency synthesis / multiplication circuit 4. Control the circuit 4. The frequency synthesizer / multiplier circuit 4 is the same as that shown in the section of the embodiment of the invention.
The control of the microwave frequency is performed by switching the settings of M1 and M2 of the frequency synthesizer / multiplier circuit 4 by the CPU 92. M1 and M2 are M1
= 16384 to 20556, M2 = 803 to 1848, and the microwave frequency fm = 90.
MHz x 76-[{(90MHz x M1 / N1) / N3 + 9
0MHz x (M2 / N2 + 1)} / N4 + 90MHz] / N
5 = 6834686275MHz- (9.95x (10
Minus 5) Hz) x (M1 + M2 x 4173),
The setting resolution is 0.1 mHz and the variable frequency range is 434 Hz. By this control, even when the atmospheric pressure changes, the frequency of the microwave corresponding to the change in the atmospheric pressure is corrected,
It does not affect the frequency f1 of the standard frequency signal. The frequency fluctuation amount Δf with respect to the atmospheric pressure change needs to be measured in advance, but when the gas cell is cylindrical with a thickness of about 1 mm, the value confirmed experimentally by the gas cell type rubidium atomic oscillator is +1 hPa. About +0 for changes in atmospheric pressure.
It produces a resonance frequency change of 7 mHz.

In order to measure the absolute pressure of atmospheric pressure (up to 1100 hPa) and the fluctuation of atmospheric pressure with high accuracy, a capacitance (diaphragm) elastic pressure gauge is usually used. Also in this embodiment, the pressure gauge is used as the atmospheric pressure measuring device 6. The principle will be briefly described with reference to FIG. 6. Lead wires 63 and 64 are connected to a diaphragm 61 and an electrode 62, which are pressure-receiving elements, respectively, and a constant amount of vacuum or reference pressure is applied between the diaphragm 61 and the electrode 62. The gas of is enclosed. At this time, when a certain pressure is applied from the measurement pressure side, the diaphragm surface is bent and the capacitance between the lead wires changes. The atmospheric pressure can be measured by comparing this capacitance value with a read reference value. As a material for the diaphragm, stainless steel, ceramics, or the like having high corrosion resistance is used.

FIG. 7 is a block diagram showing an example of the second embodiment. The reason for applying a static magnetic field to the gas cell is that there is a magnetic sublevel in the hyperfine level of the ground level described above, and the number of resonance lines due to double resonance is, for example, 7 in the case of a rubidium atom. There are 15 in the case of cesium atoms. Moreover, the frequency interval of resonance lines is determined by the strength of the static magnetic field applied, and the amount is 200-700 kHz / Oe.
[1 Oe is about 79 A / m 2]. Since only one resonance line is used as an atomic oscillator, it is necessary to separate it from other resonance lines, and a certain static magnetic field must be applied for that purpose. Further, when a static magnetic field is applied, a resonance frequency shift δf0 due to the Zeeman effect occurs, and the amount is δf0 = 574 × (H0 squared) [Hz] in the case of a rubidium atom.
(However, H0 is the strength of the static magnetic field and the unit is [Oe].) In the case of a cesium atom, δf0 = 472 × (H0 squared) [Hz]. Therefore, the Zeeman effect is used to correct the resonance frequency fluctuation amount due to the atmospheric pressure fluctuation.

The atmospheric pressure around the double resonance part 2 is measured by the atmospheric pressure measuring device 6 shown in FIG. 6, and when the atmospheric pressure changes, the amount of change is output as a voltage value ΔV. In response to this, the frequency fluctuation amount correction circuit 9 that also serves as the correction signal generation circuit 7 and the control device 8
Is to generate a current necessary to correct the shift amount Δf of the resonance frequency corresponding to the voltage value ΔV in the CPU 92 by converting the analog signal into a digital signal by the analog / digital converter (A / D converter) 91. Is sent to a digital / analog converter (D / A converter) 93, converted into an analog signal, and the correction amount ΔI of the static magnetic field coil current value is supplied to the current supply device 5.
Send to The current supply device 5 supplies the current added with the correction amount ΔI to the coil 27 of the double resonance section 2. By this control, the change in the resonance frequency due to the change in the atmospheric pressure and the change in the resonance frequency due to the correction of the static magnetic field coil current ΔI are offset, and the resonance frequency is maintained constant. Therefore,
The frequency f1 of the standard frequency signal is not affected by atmospheric pressure.

FIG. 8 shows the frequency stability characteristics actually obtained by the gas cell type rubidium atomic oscillator by the semiconductor laser pumping method of the present invention, the frequency stability characteristics of the gas cell type rubidium atomic oscillator by the conventional semiconductor laser pumping method,
It is a figure which shows the frequency stability characteristic of the gas cell type rubidium atomic oscillator by a lamp excitation system, and the frequency stability characteristic of a highly stable crystal oscillator. This will be described below with reference to the graph of FIG. FIG. 8 uses the Allan variance scale in which the two-sample variance σy2 (τ) is defined as the frequency stability scale in the time domain, the horizontal axis represents the average measurement time (τ [sec]), and the vertical axis represents the two-sample standard deviation ( σy (τ)). The portion indicated by line 8-a in the figure shows the characteristics of the conventional semiconductor laser-excited gas cell type rubidium atomic oscillator, but the average time: τ
It can be confirmed that the stability is deteriorated in the range of = (10 4) to (10 5) [sec]. The 8-a ′ line is the frequency characteristic due to atmospheric pressure fluctuation, which is obtained by calculating the Allan variance of the atmospheric pressure data and further multiplying it by the correlation coefficient between the atmospheric pressure data and the frequency data. From this, it can be seen that the fluctuation of the atmospheric pressure affects the stability of the oscillator. Average time: τ = (10 4 power) to (10 5 power) [sec] The part where the stability is deteriorated is improved as shown by the line 8-b by applying the present invention. It was The portion indicated by 8-c line is the characteristic of the gas cell type rubidium atomic oscillator by the lamp excitation system,
The part indicated by -d line is the characteristic of the high stability crystal oscillator. It is included for comparison with the characteristics (8-a line) of a semiconductor laser-excited gas cell type rubidium atomic oscillator. As described in the section of the conventional technique, as can be seen from FIG. 8, in the gas cell type rubidium atomic oscillator by the lamp excitation system, the influence of atmospheric pressure variation on the characteristic (line 8-c) is not seen.

[0026]

As described above, in the gas cell type atomic oscillator of the present invention, the atmospheric pressure is measured, and the current supplied to the coil and the frequency of the resonance microwave supplied to the double resonance part are measured based on the fluctuation amount. Since at least one of them is corrected, it is possible to provide a gas cell type atomic oscillator that suppresses deterioration of frequency stability due to fluctuations in atmospheric pressure.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a gas cell type atomic oscillator of the present invention.

FIG. 2 is a diagram showing a configuration of a first exemplary embodiment of the present invention.

FIG. 3 is a diagram showing a configuration of a frequency synthesis / multiplication circuit used in the first embodiment of the present invention.

FIG. 4 is a diagram showing a configuration of a second exemplary embodiment of the present invention.

FIG. 5 is a diagram showing a configuration of an example of the first exemplary embodiment of the present invention.

FIG. 6 is a diagram showing a configuration of an atmospheric pressure measuring device.

FIG. 7 is a diagram showing a configuration of an example of a second exemplary embodiment of the present invention.

FIG. 8 shows frequency stability characteristics actually obtained by the gas cell type rubidium atomic oscillator according to the semiconductor laser pumping method of the present invention, frequency stability characteristics of the gas cell type rubidium atomic oscillator by the conventional semiconductor laser pumping method, and lamp pumping method. It is a figure which shows the frequency stability characteristic of a gas cell type rubidium atomic oscillator, and the frequency stability characteristic of a highly stable crystal oscillator.

FIG. 9 is a diagram showing a configuration of a conventional gas cell type atomic oscillator.

FIG. 10 is a diagram showing a configuration of a double resonance part.

FIG. 11 is a diagram for explaining an optical / microwave double resonance phenomenon of atoms.

[Explanation of symbols]

 1 Excitation Light Source Section 2 Double Resonance Section 3 Frequency Signal Generation Section 4 Microwave Generation Circuit (Frequency Synthesis / Multiplication Circuit) 5 Current Supply Device 6 Atmospheric Pressure Measuring Instrument 7 Correction Signal Generation Circuit 8 Control Device 9 Frequency Fluctuation Correction Circuit 21 Gas Cell 22 Microwave Cavity Resonator 23 Photoelectric Conversion Element 24 Microwave Excitation Antenna 25 Magnetic Shield Tank 26 Constant Temperature Heater 27 Coil (Static Magnetic Field Coil) 28 Excitation Light Input Window 31 Signal Processor 32 Voltage Controlled Crystal Oscillator 41 Variable Frequency Divider 42 Variable frequency divider 61 Diaphragm 62 Electrode 63 Lead wire 64 Lead wire 91 Analog / digital converter (A / D converter) 92 CPU 93 Digital / analog converter (D / A converter)

 ─────────────────────────────────────────────────── --- Continuation of the front page (72) Inventor Masao Uehara 5-10-10 Minamiazabu, Minato-ku, Tokyo Anritsu Co., Ltd.

Claims (1)

[Claims] 1. A gas cell (21) containing an alkali metal atom and a coil (2) for generating a magnetic field in the gas cell.
7) built-in double resonance part (2), current supply device (5) for the coil, excitation light source part (1) for generating excitation light of the alkali metal atom, and double resonance part A frequency signal generator (3) for receiving a frequency signal corresponding to the output signal and a microwave generation circuit (4) for receiving the frequency signal and generating a resonance microwave of the alkali metal atom. In a gas cell type atomic oscillator comprising: an excitation light source unit made of a semiconductor laser; and an atmospheric pressure measuring device (6) for measuring an atmospheric pressure around the gas cell and outputting a signal according to the atmospheric pressure value, A correction signal generation circuit (7) for receiving a signal output from the atmospheric pressure measuring device and outputting a correction signal corresponding to the measured atmospheric pressure value, and a current for the coil and the resonance microwave receiving the correction signal. Of the frequency A gas cell type atomic oscillator, comprising: a control device (8) for controlling at least one of them, and at least one of the current supply device and the microwave generation circuit is controllable by the control device. [0001]