JP2636671B2 - Rubidium atomic oscillator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas cell type rubidium atomic oscillator which absorbs pumping light of a rubidium lamp by microwaves and calibrates the oscillation frequency of a voltage controlled crystal oscillator based on the light absorption characteristics.

[0002]

2. Description of the Related Art A rubidium atomic oscillator is an oscillator that obtains a stable standard frequency by synchronizing the oscillation frequency of a voltage controlled crystal oscillator with the transition frequency of rubidium atoms. For this synchronization, the absorption characteristic of the pumping light of the rubidium lamp in the rubidium gas cell by the microwave is used.

FIGS. 4 and 5 show a basic circuit configuration of a rubidium atomic oscillator and a basic configuration of an optical microwave unit used in the rubidium atomic oscillator, respectively. The rubidium atomic oscillator 11 includes an optical microwave unit 12, a frequency controller 13, a voltage controlled crystal oscillator 14, a frequency multiplier 15, a frequency synthesizer 16, and a frequency mixer 1
7 is comprised. The optical microwave unit 12
Are a rubidium lamp 21, a rubidium gas cell 22, a cavity 23, a C field coil 24, and a photodetector 2.
And 5.

The frequency controller 13 receives the output of the photodetector 25 in the optical microwave unit 12, and controls the oscillation frequency of the voltage controlled crystal oscillator 14 according to the output. The output of the voltage controlled crystal oscillator 14 is output to an external device (not shown), and the frequency multiplier 1
5 and output to the frequency synthesizer 16. Frequency multiplier 15
Multiplies the input frequency by a predetermined coefficient, creates a microwave, and outputs it to the frequency mixer 16. The frequency synthesizer 16 synthesizes a predetermined frequency from the output signal of the voltage controlled crystal oscillator 14 and outputs the result to the frequency mixer 17. The frequency mixer 17 mixes these to create a modulated microwave and uses a microwave supply line 26 to
This is supplied into the cavity 23 of the optical microwave unit 12.

When the frequency of the supplied microwave and the frequency of the pumping light emitted by the rubidium lamp satisfy a predetermined relationship, the pumping light is absorbed in the rubidium gas cell 22. The rubidium atomic oscillator 11
By detecting this light absorption characteristic with the photodetector 25,
Calibration of the oscillation frequency of the voltage controlled crystal oscillator having a multiplication relationship with the microwave is performed. The basic operation of the rubidium atomic oscillator is as described above.However, the problem with the rubidium atomic oscillator is that the oscillation frequency fluctuates due to changes in the ambient temperature and that the oscillation frequency fluctuates over time. was there.

Japanese Patent Laid-Open Publication No. 2-11023 discloses a rubidium atomic oscillator for compensating for a frequency change with respect to a change in the ambient temperature. FIG. 6 shows a configuration of a circuit that performs frequency compensation with the rubidium atomic oscillator. This compensation circuit includes a temperature detector 31 and an A / A
It comprises a D converter 32, a memory 33 and a D / A converter. In this rubidium atomic oscillator, frequency compensation is performed by the following procedure using this compensation circuit.

The temperature detector 31 detects the ambient temperature and outputs the detection result as an analog signal. The A / D converter 32 converts the analog signal into a digital signal and outputs the digital signal to the memory 33. In the memory 33, a current value to be supplied to the C field coil 24 is stored in advance in one-to-one correspondence with the temperature information converted into a digital signal. The memory 33 outputs a current value corresponding to the ambient temperature information to the D / A converter 34, and the D / A converter 34 supplies a current corresponding to the current value specified by the digital signal to the current supply line 27. To supply it to the C field coil 24 in the optical microwave unit 12. With such an operation,
Compensation for the frequency variation due to the ambient temperature change is performed.

A rubidium atomic oscillator for compensating for a change over time is disclosed in Japanese Patent Application Laid-Open No. 62-139413. This rubidium atomic oscillator utilizes the fact that the weaker the light to be irradiated, the smaller the change over time of the rubidium gas cell, and is provided with two rubidium gas cells.

[0009]

In a conventional rubidium oscillator which performs frequency compensation for a change in ambient temperature, frequency compensation is performed only for a change in ambient temperature. Therefore, there is a problem that when the frequency changes due to the above, sufficient compensation cannot be performed. Further, in the rubidium atomic oscillator disclosed as compensating for a change with time, two rubidium gas cells must be provided, and the device configuration becomes complicated and the oscillator itself becomes large. .

SUMMARY OF THE INVENTION An object of the present invention is to provide a rubidium atomic oscillator capable of compensating for a change in oscillation frequency due to a change in ambient temperature or a change over time in a rubidium gas cell.

[0011]

According to the first aspect of the present invention, there is provided a voltage controlled crystal oscillator for outputting a standard frequency, a rubidium lamp for emitting pumping light, and a microwave obtained by multiplying the output frequency of the voltage controlled crystal oscillator. And a cavity including a rubidium gas cell filled with rubidium atoms that absorbs pumping light from a rubidium lamp by microwaves generated by the microwave output source, and a static magnetic field in a predetermined direction is applied to the cavity. Means for applying a static magnetic field to be applied, and means for adjusting the oscillation frequency of the voltage-controlled crystal oscillator by shifting the absorption characteristic of the pumping light in the rubidium gas cell in the frequency axis direction by the intensity of the static magnetic field. To measure the level of microwaves in the cavity. And black wave level measuring means, the micro-detected by the microwave level measuring means
Calculates the difference between the wave level and the reference microwave level
Level difference calculating means, and the level difference calculating means.
Between the calculated level difference and the microwave frequency change
Relationship, the amount of microwave frequency variation and this frequency
The relationship between the static magnetic field strength and the amount of change
The values read from the storage means and the strength of the static magnetic field applied by the static magnetic field applying means are stored in advance.
Means for changing the static magnetic field strength based on the rubidium atom
An oscillator is provided.

[0012] That is, in the first aspect of the present invention is provided with a microwave level measuring means for measuring the level of the microwave in the cavity to absorb a pumping light rubidium lamp rubidium gas cell by microwave, or
The relationship between the level difference of the
Compensation for frequency fluctuations of microwaves and microwaves and fluctuations of this frequency
The relationship between the static magnetic field strength and the amount of change
A storage means for storing the information is prepared. And microwave
Microwave level detected by level measuring means
The difference between the level of the reference microwave and the level
Calculates the output of the voltage controlled crystal oscillator based on this
Read out the strength of the static magnetic field to make the frequency constant,
To the value of Confirm that there is a correlation between the microwave level in the cavity and the output frequency .
Because it was, thereby, the purpose is achieved in that to compensate for variations in the oscillation frequency due to aging changes or rubidium gas cell at ambient temperature.

[0013]

[0014]

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to embodiments.

The rubidium atomic oscillator of the present invention detects a frequency fluctuation by measuring the microwave level in the optical microwave unit, and controls the current value of the C field coil according to the detection result to compensate for the frequency. Is what you do.

First, the principle of output frequency compensation of the rubidium atomic oscillator of the present invention will be described. The relationship shown in FIG. 2 exists between the change amount ΔP of the microwave level and the change amount Δf of the output frequency. Further, there is a correlation as shown in FIG. 3 between the amount of change ΔI of the current supplied to the C field coil and the amount of change Δf of the output frequency. From these relationships, by measuring the amount of change in the microwave level, the amount of change in the frequency can be evaluated, and the current value supplied to the C field coil required to compensate for the amount of change in the frequency is calculated. You can do it. In the rubidium atomic oscillator of the present invention, this frequency compensation operation is realized by the following circuit configuration.

FIG. 1 shows the configuration of a compensation circuit for a rubidium atomic oscillator according to an embodiment of the present invention. The compensation circuit 35 includes a band-pass filter 36, a detection circuit 37, an A / D converter 38, a CPU (central processing unit) 39, and a C field control circuit 4.
0 and a memory 41. The memory 41 stores information instructing an operation to be described below, relation information between Dstd, which is a reference value of the microwave output level, and the frequency change Δf and the microwave level change ΔP shown in FIG. Further, information on the relationship between the frequency change Δf shown in FIG. 3 and the current change ΔI supplied to the C field coil is stored. The compensation circuit 35 is connected to the optical microwave unit 12 by the current supply line 27 and the microwave detection line 42.
Is connected to The optical microwave unit forms a circuit as shown in FIG. 4 by a signal line (not shown). The operation of this compensation circuit will be described below.

The band-pass filter 36 is connected to the optical microwave unit 12 by a microwave detection line 42, and extracts a microwave necessary for detecting a synchronization state from the input microwave. The detector 37 converts the output level of the extracted microwave into a DC voltage corresponding thereto, and the A / D converter 38 converts the DC voltage into a digital signal D. The CPU 39 calculates the difference ΔD between the digital signal D and the reference signal Dstd, and uses the relation information between ΔD and Δf stored in the memory 41 to calculate
The amount of frequency fluctuation Δf that has occurred is determined. Next, in order to compensate for this frequency variation Δf, the variation ΔI of the value of the current supplied to the C field coil is represented by Δf stored in the memory 41.
, And a new current value I is set by adding the obtained current change value ΔI to the current current value. The C field control circuit 40 supplies the current value I indicated by the digital signal to the C field coil as an analog signal,
The static magnetic field applied to the rubidium gas cell is changed. As a result, the frequency fluctuation Δf is canceled.

Also, the compensation circuit may be configured such that the microwave supplied to the optical microwave unit is branched and the detection is performed using the microwave, without detecting the microwave level in the optical microwave unit. Good.

[0021]

According to the invention of claim 1, wherein, as described in the foregoing, the change of the output frequency of the rubidium atom oscillator, carried out by measurement of the microwave level in the optical microwave unit, according to the detection result As a result, it is possible to perform frequency compensation for frequency fluctuations due to ambient temperature and changes over time. For this reason, it is possible to obtain a rubidium atomic oscillator with less frequency fluctuation due to temperature change and temporal change.
In addition, the microwave level difference and frequency change amount are stored in the storage means.
And the amount of microwave frequency fluctuation and this frequency
Of the change in static magnetic field strength to compensate
Since the parameters are stored in advance, changes in the static magnetic field
Changes can be made quickly.

[0022]

[Brief description of the drawings]

FIG. 1 is a block diagram showing a connection relationship between an optical microwave unit and a frequency compensation circuit in a rubidium atomic oscillator according to an embodiment of the present invention.

FIG. 2 is a relationship diagram showing a relationship between a change amount of a microwave level and a change amount of an output frequency of the rubidium atomic oscillator of the embodiment.

FIG. 3 is a relationship diagram showing a relationship between a change amount of a current applied to a C-field coil of the rubidium atomic oscillator of the embodiment and a change amount of an output frequency.

FIG. 4 is a block diagram showing a basic circuit configuration of a conventional rubidium atomic oscillator.

FIG. 5 is a configuration diagram showing a basic configuration of an optical microwave unit of a conventional rubidium atomic oscillator.

FIG. 6 is a block diagram illustrating a circuit configuration of a frequency compensating circuit of a conventional rubidium atomic oscillator that performs frequency compensation with respect to an ambient temperature.

[Description of Symbols] 11 ... Rubidium atomic oscillator 12 ... Optical microwave unit 13 ... Frequency controller 14 ... Voltage controlled crystal oscillator 15 ... Frequency multiplier 16 ... Frequency synthesizer 17 ... Frequency mixer 21 ... Rubidium lamp 22 ... Rubidium gas cell Reference Signs List 23 Cavity 24 C field coil 25 Photodetector 26 Microwave supply line 27 Current supply line 30, 35 Compensation circuit 31 Temperature detector 32, 38 A / D converter 33, 41 Memory 34 ... D / A converter 36 ... Bandpass filter 37 ... Detection circuit 39 ... CPU (central processing circuit) 40 ... C field control circuit 42 ... Microwave detection line

Claims (1)

(57) [Claims] A voltage controlled crystal oscillator for outputting a standard frequency; a rubidium lamp for emitting pumping light; a microwave output source for outputting a microwave obtained by multiplying an output frequency of the voltage controlled crystal oscillator; A cavity including a rubidium gas cell filled with rubidium atoms for absorbing pumping light from the rubidium lamp by a microwave generated by a wave output source; a static magnetic field applying means for applying a static magnetic field in a predetermined direction to the cavity; Microwave level measuring means for measuring the level of the microwaves within; level difference calculating means for calculating the difference between the level of the microwave detected by the microwave level measuring means and the level of the reference microwave; The level difference calculated by the level difference calculating means and the microwave A storage unit in which the relationship between the frequency change amount and the relationship between the microwave frequency change amount and the change amount of the static magnetic field intensity for compensating the change in the frequency are respectively stored in advance, and the relationship is applied by the static magnetic field applying unit. Magnetic field strength changing means for changing the strength of the static magnetic field based on the value read from the storage means, and changing the static magnetic field strength by the static magnetic field strength changing means.
Pumping in the rubidium gas cell
By shifting the light absorption characteristics in the frequency axis direction,
Voltage control A voltage control that adjusts the oscillation frequency of the crystal oscillator.
A rubidium atomic oscillator comprising a crystal oscillator oscillation frequency adjusting means .