JP6686640B2 - Quantum interference device, atomic oscillator, and electronic device - Google Patents

Description

  The present invention relates to a quantum interference device, an atomic oscillator, an electronic device and a moving body.

An atomic oscillator that oscillates based on energy transition of atoms of an alkali metal such as rubidium or cesium is known as an oscillator having highly accurate oscillation characteristics in the long term (see, for example, Patent Document 1).

For example, the rubidium atomic oscillator described in Patent Document 1 is an optical microwave unit that is excited by the resonance frequency of a rubidium atom, a photodetector that detects the intensity of light that has passed through the optical microwave unit, and an output of the photodetector. Amplifier that amplifies the signal, a phase detector that detects the phase of the frequency error signal that appears in the amplifier, a loop filter that integrates the output signal of the phase detector, and a voltage control that oscillates a predetermined frequency based on the voltage of the loop filter. Type crystal oscillator, an oscillating circuit for giving a low-frequency signal for modulating the phase of the microwave, and a phase modulation / multiplication unit for phase-modulating the oscillation signal of the voltage-controlled crystal oscillator and multiplying it to the microwave There is.

JP, 2008-258862, A

In the rubidium atomic oscillator described in Patent Document 1, the frequency of phase modulation in the phase modulation multiplier is 100 Hz because there is a constraint based on the response speed of the rubidium atom to light.
It is lower than the order. Along with that, conventionally, the phase detector and loop filter have
It is configured by using analog components such as a tuning circuit in a low frequency band of 00 to 300 Hz, a bandpass filter, and a band reject circuit. In general, analog components in the low frequency band are larger than analog components in the high frequency band. Therefore, the conventional atomic oscillator has a problem that it is difficult to reduce the size.

An object of the present invention is to provide a quantum interference device, an atomic oscillator, an electronic device, and a moving body that can be miniaturized while having excellent frequency characteristics.

The above object is achieved by the present invention described below.
The quantum interference device of the present invention is an atomic cell in which alkali metal atoms are encapsulated,
A light source unit that emits light for exciting the alkali metal atom,
A photodetector that outputs a signal according to the intensity of the light that has passed through the atomic cell,
A frequency conversion unit that outputs a signal obtained by frequency-converting the signal from the photodetection unit to a higher frequency side using digital processing,
A detection unit that detects the signal from the frequency conversion unit.

According to such a quantum interference device, since the frequency conversion unit frequency-converts the signal from the photodetection unit to the higher frequency side, it is possible to increase the frequency band of the analog component forming the detection unit. As a result, the quantum interference device can be downsized. Further, since digital processing is used for frequency conversion of the frequency conversion unit, the number of analog components in the frequency conversion unit can be reduced, and in this respect also, the quantum interference device can be downsized. Further, the frequency conversion in the frequency conversion unit can increase the frequency difference between the frequency component to be detected by the detection unit and other frequency components. Therefore, it is possible to perform the detection in the detection unit with high accuracy while simplifying the configuration of the detection unit. For this reason, it is possible to provide a quantum interference device that can be miniaturized while having excellent frequency characteristics.

In the quantum interference device of the present invention, a voltage-controlled crystal oscillator that outputs a signal having a frequency according to a voltage signal,
A signal from the voltage-controlled crystal oscillator, a multiplication and synthesis unit that frequency-multiplies and phase-modulates a frequency signal according to the transition frequency between the ground levels of the alkali metal atoms to generate a microwave signal,
It is preferable that the frequency conversion unit frequency-converts a frequency component according to the frequency of the phase modulation.
As a result, the detection in the detection unit can be performed at a frequency higher than the frequency of the phase modulation of the multiplication / synthesis unit.

The quantum interference device of the present invention includes an oscillator,
The multiplying / combining unit performs phase modulation using digital processing based on a signal from the oscillator, and generates the microwave signal having a frequency component that changes stepwise,
It is preferable that the detection section performs the detection using a signal from the oscillator.
Since digital processing is used for phase modulation of the signal from the voltage controlled crystal oscillator, the number of analog components in the low frequency band can be reduced, and as a result, the quantum interference device can be miniaturized. Further, since the microwave signal has a frequency component that changes in a stepwise manner, it is possible to perform detection in the detection unit with an S / N ratio that is superior to that in the case where the frequency is changed in a binary manner. Excellent short-term frequency stability can be achieved.

In the quantum interference device of the present invention, an oscillator,
A frequency divider for frequency-dividing the signal from the oscillator,
The multiplication and synthesis unit performs the phase modulation using the signal from the frequency divider,
It is preferable that the detection section performs the detection using a signal from the oscillator.
This allows the detection unit to perform synchronous detection while simplifying the configuration of the multiplication / synthesis unit.

In the quantum interference device of the present invention, it is preferable that the frequency conversion unit has a Fourier transform circuit.
Thereby, the frequency conversion in the frequency conversion unit can be performed with high accuracy.

In the quantum interference device of the present invention, it is preferable that the frequency conversion unit converts a frequency of a signal to be detected by the detection unit into a frequency of 1 kHz or more and 100 MHz or less.
As a result, the frequency band of the analog component forming the detection unit can be made sufficiently high, and as a result, the quantum interference device can be effectively downsized.

An atomic oscillator of the present invention comprises the quantum interference device of the present invention.
According to such an atomic oscillator, it is possible to achieve miniaturization while providing excellent frequency characteristics.

The atomic oscillator of the present invention is an atomic cell in which an alkali metal atom is encapsulated,
A light source unit that emits light for exciting the alkali metal atom,
A photodetector that outputs a signal according to the intensity of the light that has passed through the atomic cell,
A frequency conversion unit that outputs a signal obtained by frequency-converting the signal from the photodetection unit to a higher frequency side using digital processing,
A detection unit that detects the signal from the frequency conversion unit.
According to such an atomic oscillator, it is possible to achieve miniaturization while providing excellent frequency characteristics.

In the atomic oscillator of the present invention, it is preferable that the light emitted from the light source unit includes a resonant light pair that causes an electromagnetically induced transmission phenomenon in the alkali metal atom.
Therefore, compared to an atomic oscillator that uses the double resonance phenomenon of light and microwaves,
The size can be greatly reduced.

The electronic equipment of the present invention is equipped with the quantum interference device of the present invention.
According to such an electronic device, it is possible to achieve miniaturization while improving the frequency characteristics of the quantum interference device.

A mobile object of the present invention is characterized by including the quantum interference device of the present invention.
According to such a moving body, the quantum interference device can be miniaturized while having excellent frequency characteristics.

It is a schematic diagram which shows schematic structure of the atomic oscillator (quantum interference apparatus) which concerns on 1st Embodiment of this invention. It is a figure for demonstrating the energy state of an alkali metal. 6 is a graph showing the relationship between the frequency difference between the first light and the second light emitted from the light source unit and the intensity of the light detected by the light detection unit. 3 is a graph illustrating the frequency of the output signal of the multiplication / synthesis unit included in the atomic oscillator shown in FIG. 1. 7 is a graph illustrating the relationship between the output signal of the multiplication / synthesis unit and the EIT signal. 6 is a graph illustrating the output signal of the photodetector when the frequency band of the output signal of the multiplication / synthesis unit is in the range indicated by A in FIG. 5. 6 is a graph illustrating the output signal of the photodetector when the frequency band of the output signal of the multiplication / synthesis unit is in the range indicated by B in FIG. 5. 6 is a graph illustrating the output signal of the photodetector when the frequency band of the output signal of the multiplication / synthesis unit is in the range indicated by C in FIG. 5. It is a figure explaining the frequency conversion in the frequency conversion part with which the atomic oscillator shown in FIG. 1 is equipped. It is a schematic diagram which shows schematic structure of the atomic oscillator (quantum interference apparatus) which concerns on 2nd Embodiment of this invention. It is a figure which shows embodiment of the electronic device of this invention. It is a figure showing an embodiment of a mobile of the present invention.

Hereinafter, a quantum interference device, an atomic oscillator, an electronic device and a moving body of the present invention will be described in detail based on preferred embodiments shown in the accompanying drawings.

1. Atomic oscillator (quantum interference device)
First, an atomic oscillator of the present invention (an atomic oscillator including the quantum interference device of the present invention) will be described. In the following, an example in which the quantum interference device and the atomic oscillator of the present invention are applied to an atomic oscillator utilizing the quantum interference effect will be described.However, the quantum interference device of the present invention includes, in addition to the atomic oscillator, a magnetic sensor, The atomic oscillator of the present invention is also applicable to a quantum memory and the like, and is also applicable to an atomic oscillator utilizing the double resonance phenomenon, for example.

<First Embodiment>
FIG. 1 is a schematic diagram showing a schematic configuration of an atomic oscillator (quantum interference device) according to a first embodiment of the present invention. FIG. 2 is a diagram for explaining the energy state of an alkali metal. FIG. 3 is a graph showing the relationship between the frequency difference between the first light and the second light emitted from the light source unit and the intensity of the light detected by the light detection unit.

The atomic oscillator 1 shown in FIG. 1 has a CPT (Coherent Population) which is one of the quantum interference effects.
Trapping) is used, and a clock signal with high frequency accuracy can be output.

As shown in FIG. 1, the atomic oscillator 1 has a quantum interference unit 2 and a circuit unit 10 electrically connected to the quantum interference unit 2. The quantum interference unit 2 includes a light source 22 (light source unit) that emits light, an atomic cell 21 (gas cell) in which an alkali metal atom such as a rubidium atom or a cesium atom is sealed, and a photodetector 23 (photodetection unit). And. Circuit part 10
Is an amplifier 31, a detection circuit 32, a modulation circuit 33, a low frequency oscillator 34, and a drive circuit 35.
, A frequency conversion unit 5, a detection circuit 41, a voltage control type crystal oscillator 42 (VCXO: Voltag
e Controlled Crystal Oscillators), a multiplication / synthesis unit 43, and an oscillator 44.

In this atomic oscillator 1, when two resonance lights having different wavelengths are simultaneously applied to an alkali metal atom, the two resonance lights are transmitted by the alkali metal without being absorbed by the alkali metal (EIT:
Electromagnetically Induced Transparency) phenomenon is used. Such atomic oscillator 1
Stabilizes the output signal of the voltage controlled crystal oscillator 42 (VCXO) at a predetermined frequency by using an EIT signal which is a steep signal generated with the EIT phenomenon. Then, the atomic oscillator 1 outputs the output signal of the voltage controlled crystal oscillator 42 (VCXO) as a clock signal of a desired frequency.

Hereinafter, each part of the atomic oscillator 1 will be sequentially described.
<Quantum interference unit>
As described above, the quantum interference unit 2 illustrated in FIG. 1 includes the light source 22 (light source section), the atom cell 21 (gas cell), and the photodetector 23 (photodetection section).

(Light source part)
The light source 22 has a function of emitting light including first resonance light and second resonance light that excite the alkali metal atoms in the atomic cell 21. The light emitted from the light source 22 enters the atomic cell 21.

The light source 22 is not particularly limited as long as it can emit the above-mentioned light. For example, a vertical cavity surface emitting laser (VCSEL: Vertical Cavity Surface Emitting Laser) is used.
) Etc. semiconductor laser etc. can be used.

(Atomic cell)
In the atomic cell 21, alkali metal such as gaseous rubidium, cesium, sodium (
Alkali metal atom) is enclosed. Further, in the atomic cell 21, a rare gas such as argon or neon or an inert gas such as nitrogen may be enclosed as a buffer gas together with a gaseous alkali metal, if necessary.

As shown in FIG. 2, the alkali metal atom has a three-level energy level consisting of two different ground levels (first ground level and second ground level) and an excitation level. The first ground level is an energy level lower than the second ground level.

Here, the resonance light (first resonance light) having a frequency ω ₁ corresponding to the energy difference between the first ground level and the excitation level, and the energy difference between the second ground level and the excitation level When the resonance light (first resonance light) having the corresponding frequency ω ₁ is individually irradiated to the alkali metal atom, light absorption occurs. On the other hand, when the first resonance light and the second resonance light (resonance light pair) are simultaneously irradiated, both the first resonance light and the second resonance light are transmitted without being absorbed by the alkali metal atom (EIT). ) Phenomenon occurs. That is, in this EIT phenomenon, the first resonance light and the second resonance light are simultaneously irradiated to the alkali metal atoms, and the frequency difference (ω ₁ −) between the frequency ω ₁ of the first resonance light and the frequency ω ₂ of the second resonance light is generated. ω ₂ ) occurs when the frequency ω ₀ corresponds to the energy difference ΔE between the first and second ground levels. Therefore, as shown in FIG. 3, the light absorption rate (light transmittance) in the alkali metal atoms of the first resonance light and the second resonance light changes according to the frequency difference (ω ₁ −ω ₂ ), and the frequency difference ( When ω ₁ −ω ₂ ) coincides with the frequency ω ₀ , the EIT phenomenon occurs, and the intensities of the first resonance light and the second resonance light transmitted through the alkali metal atoms sharply increase. Such a steep signal is called an EIT signal. This EIT signal has an eigenvalue determined by the type of alkali metal atom. Therefore, by using such an EIT signal as a reference, a highly accurate oscillator can be constructed.

For example, when the alkali metal atom is a cesium atom, the frequency ω ₀ corresponding to the energy difference ΔE is 9.1926 GHz, and therefore the cesium atom has two types of frequency difference (ω ₁ −ω ₂ ) of 9.1926 GHz. When the above light is simultaneously emitted, the EIT signal is detected.

The atomic cell 21 is heated by a heater (not shown) driven based on the detection result of a temperature sensor (not shown) that detects the temperature of the atomic cell 21. Thereby, the alkali metal in the atomic cell 21 can be maintained in a gaseous state with an appropriate concentration. Further, in the vicinity of the atomic cell 21, for example, a magnetic field generation unit (not shown) having a coil for applying a magnetic field to the alkali metal by energization is provided. By the magnetic field from this magnetic field generation unit, the gap between a plurality of different energy levels in which the alkali metal atoms are degenerated can be expanded by Zeeman splitting, and the resolution can be improved. As a result, the accuracy of the oscillation frequency of the atomic oscillator 1 can be improved.

In addition, optical components such as a wave plate, a neutral density filter, a lens, and a polarizing plate may be arranged between the light source 22 and the atomic cell 21 described above.

(Light detector)
The photodetector 23 detects the light transmitted through the atomic cell 21 (in particular, the resonance light pair composed of the first resonance light and the second resonance light) and outputs a detection signal corresponding to the intensity of the detected light. To do.

The photodetector 23 is not particularly limited as long as it can detect the intensity of light described above, but for example, a photodetector (light receiving element) such as a photodiode can be used.

<Circuit part>
The circuit unit 10 shown in FIG. 1 includes the amplifier 31, the detection circuit 32, and the modulation circuit 3 as described above.
3, a low frequency oscillator 34, a drive circuit 35, a frequency conversion unit 5, a detection circuit 41, a voltage control type crystal oscillator 42, a multiplication and synthesis unit 43, an oscillator 44, and a frequency divider 45. Have.

The amplifier 31 amplifies the output signal of the photodetector 23. The output signal of the amplifier 31 is input to each of the detection circuit 32 and the frequency conversion unit 5.
The detection circuit 32 synchronously detects the output signal of the amplifier 31 using the output signal (oscillation signal) of the low-frequency oscillator 34 that oscillates at a low frequency of about several Hz to several hundred Hz. The modulation circuit 33 modulates the output signal of the detection circuit 32 using the output signal (oscillation signal) of the low-frequency oscillator 34 as a modulation signal in order to enable the detection by the detection circuit 32.

The drive circuit 35 finely adjusts the bias current according to the output signal of the modulation circuit 33, and
Set the bias current supplied to 2 (set the center wavelength of the light emitted from the light source 22)
. That is, the central wavelength of the light emitted from the light source 22 is controlled (finely adjusted) by the feedback loop passing through the light source 22, the atomic cell 21, the photodetector 23, the detection circuit 32, the modulation circuit 33, and the drive circuit 35, and is stabilized. Note that this feedback loop may be performed only by analog processing, but digital processing can be used.

Further, the drive circuit 35 supplies the light source 22 with the current (modulation current) of the frequency component of the output signal of the multiplication / combination unit 43, which will be described later, superimposed on the bias current finely adjusted as described above. When the light emitted from the light source 22 is frequency-modulated by the modulation current, light having a center frequency corresponding to the bias current and a plurality of sets of frequencies on both sides of which are shifted as sideband light by the frequency of the modulation current. Light is emitted.

The frequency converter 5 frequency-converts the output signal of the amplifier 31 to the side where the frequency becomes higher. In particular, the frequency converter 5 performs frequency conversion using digital processing. Specifically, the frequency conversion unit 5 has a Fourier transform circuit 51, and the Fourier transform circuit 51 performs a frequency transform on the output signal of the amplifier 31 by performing a Fourier transform. The matters regarding the frequency conversion unit 5 will be described in detail later.

The detection circuit 41 synchronously detects the output signal of the frequency conversion unit 5 using the output signal of the oscillator 44. The detection circuit 41 includes a phase detector 411 that synchronously detects the output signal of the amplifier 31 using the output signal of the oscillator 44, and a low-pass filter 412 (loop filter) to which the output signal of the phase detector 411 is input. Have. The low pass filter 412 outputs a voltage signal according to the detection result of the photodetector 23. Then, the output signal of the low-pass filter 412 is input to the voltage-controlled crystal oscillator 42.

In the voltage controlled crystal oscillator 42, the oscillation frequency of the voltage controlled crystal oscillator 42 (VCXO) is finely adjusted according to the magnitude of the output signal of the detection circuit 41. Voltage controlled crystal oscillator 42 (
The oscillation frequency of (VCXO) is not particularly limited, but is about 10 MHz, for example. The output signal of the voltage-controlled crystal oscillator 42 is input to the multiplication / combination unit 43 and used as the output signal of the atomic oscillator 1.

The multiplication / combination unit 43 multiplies the frequency of the output signal of the voltage-controlled crystal oscillator 42 and phase-modulates it to output a microwave signal. The multiplication / combination unit 43 includes a fractional phase synchronization circuit 431 (F-PLL) that frequency-multiplies the output signal of the voltage-controlled crystal oscillator 42,
And a control unit 432 that gradually changes the multiplication rate of the fractional phase synchronization circuit 431 based on the output signal of the oscillator 44 by digital processing. As described above, the multiplication / combination unit 43 has a variable multiplication ratio, and changes the multiplication ratio stepwise. As a result, the output signal of the voltage controlled crystal oscillator 42 is phase-modulated. Such an output signal of the multiplication / combination unit 43 has a frequency component (microwave component) for frequency modulation of the light of the light source 22 described above and a frequency component (detection frequency component) for enabling detection by the detection circuit 41. ) And, including. Then, the multiplication / synthesis unit 4
The output signal of No. 3 is input to the drive circuit 35. The matters regarding the multiplication / combination unit 43 will be described later in detail.

The oscillator 44 oscillates at a frequency of 10 kHz or more and 10 MHz or less. And oscillator 4
The output signal of No. 4 is input to each of the control unit 432 and the phase detector 411.

Light source 22, atomic cell 21, photodetector 23, amplifier 31, frequency converter 5, detection circuit 41
, A pair of sideband lights emitted from the light source 22 by a feedback loop that passes through the voltage controlled crystal oscillator 42, the multiplication / combination unit 43, and the drive circuit 35 becomes a resonant light pair that causes the EIT phenomenon in the alkali metal atom. It is controlled (fine-tuned).

As described above, the EIT signal, which is a steep signal generated due to the EIT phenomenon, is detected by the photodetector 23, and the EIT signal is used as the reference signal to output the output signal of the voltage-controlled crystal oscillator 42 to a predetermined value. Stabilize at the frequency of. Then, the output signal of the voltage-controlled crystal oscillator 42 is output to the outside. At that time, the output signal of the voltage-controlled crystal oscillator 42 is, if necessary,
For example, a frequency conversion circuit (not shown) such as a DDS (Direct Digital Synthesizer) may convert the frequency to a desired frequency at a predetermined frequency conversion rate.

(Multiply synthesizer)
Hereinafter, the multiplication / combination unit 43 and matters related thereto will be described in detail.
FIG. 4 is a graph for explaining the frequency of the output signal of the multiplication / synthesis unit included in the atomic oscillator shown in FIG.

The fractional phase synchronization circuit 431 included in the multiplication / combination unit 43 has, for example, a programmable frequency divider whose frequency division ratio is variable, and the frequency multiplication ratio can be changed by changing the frequency division ratio of the frequency divider. Has become. The control unit 432 included in the multiplication / combination unit 43 is, for example, a CPU
By controlling the frequency division ratio of the programmable frequency divider based on the output signal of the oscillator 44, the multiplication rate of the fractional phase synchronization circuit 431 is changed stepwise by digital processing.

As described above, the output signal of the fractional phase synchronization circuit 431, that is, the output signal of the multiplication / combination unit 43, is the frequency component (microwave component) for frequency modulation of the light of the light source 22.
And a frequency component for enabling detection by the detection circuit 41. As shown by the solid line a in FIG. 4, the frequency of the output signal of the multiplication / combination unit 43 has an amplitude Δf and a period T with the frequency f ₀ of the frequency component for frequency modulation of the light of the light source 22 as the center. Changes periodically. In particular, the frequency of the output signal of the multiplication / combination unit 43 changes stepwise based on the output signal of the oscillator 44. Further, the frequency of the output signal of the multiplication / combination unit 43 changes so as to follow the sine waveform shown by the alternate long and short dash line b in FIG.

When the frequency of the output signal of the frequency divider 45 is fb, the cycle T is equal to the cycle 1 / fb of the output signal of the frequency divider 45. That is, the frequency of the detection frequency component of the output signal of the multiplication / combination unit 43 is equal to the frequency fb of the output signal of the frequency divider 45. This allows the detection circuit 41 to synchronously detect a change in the output signal of the photodetector 23 based on the output signal of the multiplication / combination unit 43.
The frequency fb is fa / N1 when the frequency of the output signal of the oscillator 44 is fa and the frequency division ratio of the frequency divider 45 is N1.

The frequency change frequency N (the number of steps) within the cycle T of the output signal of the frequency multiplication / combination unit 43 is equal to the frequency division ratio N1 of the frequency divider 45. In FIG. 4, for convenience of explanation, the multiplication / combination unit 43
, The frequency of the output signal changes in 10 steps per cycle, but the frequency change frequency N (step number) within the cycle T of the output signal of the multiplication / combination unit 43 is 2 steps or more per half cycle. However, it is optional. However, from the viewpoint of increasing the SN ratio, the number of such changes is preferably 100 times or more and 10000 times or less.

The light of the light source 22 using the output signal of the multiplication / combination unit 43 as described above is generated by the atomic cell 21.
And is detected by the photodetector 23. At that time, in the output signal (current signal) of the photodetector 23, the deviation of the frequency f _{0 from} the frequency ω ₀ corresponding to the energy difference ΔE between the first and second ground levels of the alkali metal described above. A change in the waveform according to (error) appears as an error signal.

FIG. 5 is a graph illustrating the relationship between the output signal of the multiplication / synthesis unit and the EIT signal. FIG. 6 is a graph for explaining the output signal of the photodetector when the frequency band of the output signal of the multiplication / synthesis unit is in the range indicated by A in FIG. FIG. 7 is a graph for explaining the output signal of the photodetector when the frequency band of the output signal of the multiplication / synthesis unit is in the range indicated by B in FIG. FIG. 8 is a graph for explaining the output signal of the photodetector when the frequency band of the output signal of the multiplication / synthesis unit is in the range indicated by C in FIG.

The frequency band (frequency sweep range) of the output signal of the multiplication / combination unit 43 is the range A shown in FIG.
As shown in FIG. 6, the output signal (error signal) of the photodetector 23 cyclically changes at the above-described cycle T when it is on the one side (low frequency side) with respect to the frequency ω ₀ . . Further, when the frequency band of the output signal of the multiplication / combination unit 43 is on the other side (high frequency side) with respect to the frequency ω ₀ as in the range B shown in FIG. 5, the output signal of the photodetector 23 is As shown in FIG. 7, the phase is cyclically changed at a cycle T with a phase difference of 180 degrees from that in the range A described above. Therefore, whether the frequency band of the output signal of the multiplication / combination unit 43 is on the one side or the other side with respect to the frequency ω ₀ can be determined based on the output signal of the photodetector 23.

Further, when the frequency band of the output signal of the multiplication / combination unit 43 includes the frequency ω ₀ as in the range C shown in FIG. 5, the output signal of the photodetector 23 becomes as shown in FIG. In particular, when the frequency f ₀ of the output signal of the multiplier / synthesizer 43 matches the frequency ω ₀ , the output signal of the photodetector 23 is
As shown in FIG. 8, it periodically changes at a cycle T / 2 that is half the cycle T described above. Therefore, it can be determined based on the output signal of the photodetector 23 whether the frequency band of the output signal of the multiplication / combination unit 43 is on one side or the other side with respect to the frequency ω ₀ or includes the frequency ω _0. it can. Further, if the waveforms for each cycle T / 2 are equal to each other, it can be determined that the frequency f ₀ of the output signal of the multiplication / combination unit 43 matches the frequency ω ₀ .

Using the error signal is waveform changes in accordance with the deviation of the frequency f ₀ with respect to the frequency omega ₀ (error) As described above, as the frequency f ₀ of the output signal of the multiplier combining unit 43 coincides with the frequency omega _0, The detection circuit 41 controls the control voltage of the voltage-controlled crystal oscillator 42, so that the output signal of the desired frequency f can be obtained.
The output signal (error signal) of the photodetector 23 as described above is frequency-converted by the frequency converter 5 after being amplified by the amplifier 31.

(Frequency converter)
Hereinafter, the frequency conversion unit 5 and matters related thereto will be described in detail.
FIG. 9 is a diagram for explaining frequency conversion in the frequency conversion unit included in the atomic oscillator shown in FIG.

As described above, the frequency conversion unit 5 frequency-converts the output signal of the amplifier 31 (hereinafter, also referred to as “error signal”) to the higher frequency side by using digital processing. More specifically,
As shown in FIG. 9, the frequency of the error signal is converted from fb to fa. As a result, the detection circuit 41 can synchronously detect the error signal at the frequency fa.

Here, the frequency conversion unit 5 performs frequency conversion while suppressing the intensity change of the error signal. Further, the frequency conversion unit 5 increases the frequency difference between the desired frequency component of the error signal and the other frequency components in accordance with the frequency conversion. Thereby, the detection accuracy of the detection circuit 41 can be improved.
In the present embodiment, as described above, the frequency conversion unit 5 has the Fourier transform circuit 51,
The Fourier transform circuit 51 frequency-converts the output signal of the amplifier 31 through a process of performing Fourier transform. The Fourier transform circuit 51 performs, for example, a fast Fourier transform (FFT), and is not limited to hardware, and can be configured using an algorithm or software. Further, the Fourier transform circuit 51 can use not only analog processing but also digital processing.

As described above, the atomic oscillator 1 which is a kind of the quantum interference device described above includes the atomic cell 21 in which the alkali metal atoms are encapsulated, the light source 22 which is the light source section, and the light detection section which is the light detection section. The device 23, the frequency conversion unit 5, and the detection circuit 41 that is a detection unit. Here, the light source 22 emits light that excites the alkali metal atoms. The photodetector 23 is the atomic cell 2
It outputs a signal corresponding to the intensity of the light passing through 1. The frequency conversion unit 5 outputs a signal obtained by frequency-converting the signal from the photodetector 23 to the side where the frequency becomes higher by using digital processing. The detection circuit 41 detects the signal from the frequency conversion unit 5.

According to such an atomic oscillator 1, since the frequency conversion unit 5 frequency-converts the signal from the photodetector 23 to the side where the frequency becomes higher, the frequency band of the analog components constituting the detection circuit 41 can be increased. As a result, the atomic oscillator 1 can be downsized. Moreover, since digital processing is used for frequency conversion of the frequency conversion unit 5, the number of analog components in the frequency conversion unit 5 can be reduced, and in this respect also, the atomic oscillator 1 can be downsized. In addition, the frequency conversion in the frequency conversion unit 5 can increase the frequency difference between the frequency component to be detected by the detection circuit 41 and other frequency components. Therefore, the detection circuit 41
It is possible to perform the detection in the detection circuit 41 with high accuracy while simplifying the configuration of. For this reason, it is possible to provide the atomic oscillator 1 that can be miniaturized while having excellent frequency characteristics.

Further, the atomic oscillator 1 responds to the voltage controlled crystal oscillator 42 that outputs a signal having a frequency corresponding to the voltage signal, and the signal from the voltage controlled crystal oscillator 42 according to the transition frequency between the ground levels of the alkali metal atoms. And a frequency multiplication / combining unit 43 that frequency-multiplies the frequency and performs phase modulation to generate a microwave signal. Then, the frequency conversion unit 5 frequency-converts the frequency of the error signal, that is, the frequency component corresponding to the frequency of the phase modulation. As a result, the multiplication / synthesis unit 43
The detection in the detection circuit 41 can be performed at a frequency higher than the frequency of the phase modulation.

Further, the atomic oscillator 1 includes an oscillator 44, and the multiplication / combination unit 43 phase-modulates the signal from the oscillator 44 using digital processing to generate a microwave signal having a frequency component that changes stepwise. To do. Then, the detection circuit 41 performs detection using the signal from the oscillator 44. Thereby, since the digital processing is used for the phase modulation of the signal from the voltage controlled crystal oscillator 42, the number of analog components in the low frequency band can be reduced, and as a result, the atomic oscillator 1 can be downsized. . Further, since the microwave signal has a frequency component that changes stepwise, it is possible to perform detection in the detection circuit 41 with an excellent S / N ratio as compared with the case where the frequency is changed in a binary manner. , Can achieve excellent short-term frequency stability.

Further, the frequency conversion unit 5 has the Fourier transform circuit 51, and thus the frequency conversion unit 5
The frequency conversion can be performed with high accuracy.

Here, the frequency conversion unit 5 preferably converts the frequency of the signal to be detected by the detection circuit 41, which is the detection unit, into a frequency of 1 kHz or more and 100 MHz or less. As a result, the frequency band of the analog components forming the detection circuit 41 can be made sufficiently high, and as a result, the atomic oscillator 1 can be effectively downsized.

Further, the atomic oscillator 1 is an atomic oscillator that utilizes the quantum interference effect. That is, the light source 2
The light emitted by 2 includes a resonance light pair that causes an electromagnetically induced transmission phenomenon in the alkali metal atom.
As a result, the size of the atomic oscillator can be significantly reduced as compared with an atomic oscillator that uses the double resonance phenomenon of light and microwaves.

<Second Embodiment>
Next, a second embodiment of the present invention will be described.

FIG. 10 is a schematic diagram showing a schematic configuration of an atomic oscillator (quantum interference device) according to the second embodiment of the present invention.

The present embodiment is the same as the above-described first embodiment except that the configuration of the multiplication / synthesis unit is different.

In the following description, the second embodiment will be described focusing on the differences from the first embodiment, and the description of the same matters will be omitted. Further, in FIG. 10, the same components as those in the above-described embodiment are designated by the same reference numerals.

The atomic oscillator 1A shown in FIG. 10 includes a circuit unit 1 having a multiplication / synthesis unit 43A and a frequency divider 45.
With 0A. In this circuit section 10A, the output signal of the oscillator 44 is input to each of the phase detector 411 and the frequency divider 45. The frequency divider 45 frequency-divides the output signal of the oscillator 44 so that the output signal has a low frequency of about several Hz to several hundred Hz.

The multiplication / combination unit 43A includes a modulation circuit 433 and a phase synchronization circuit 434 (PLL).

The modulation circuit 433 modulates the output signal of the voltage-controlled crystal oscillator 42 using the output signal of the frequency divider 45 as a modulation signal to enable the detection by the detection circuit 41.

The phase synchronization circuit 434 converts the output signal of the modulation circuit 433 at a constant frequency conversion rate (multiplication ratio) and outputs a microwave signal.

As described above, the atomic oscillator 1 of the present embodiment includes the oscillator 44 and the frequency divider 45 that frequency-divides the signal from the oscillator 44. Then, the multiplication / combination unit 43A performs phase modulation using the signal from the frequency divider 45. Further, the detection circuit 41, which is a detection unit, performs detection using the signal from the oscillator 44. As a result, the detection circuit 41 can perform synchronous detection while simplifying the configuration of the multiplication / synthesis unit 43A.
Also according to the second embodiment as described above, it is possible to reduce the size while making the frequency characteristic excellent.

2. Electronic Device Hereinafter, the electronic device of the present invention will be described.

FIG. 11 is a diagram showing an embodiment of the electronic device of the invention.
The positioning system 100 (electronic device) shown in FIG. 11 includes a GPS satellite 200 and a base station device 3.
00 and a GPS receiver 400.

The GPS satellite 200 transmits positioning information (GPS signal).
The base station device 300 includes, for example, an antenna 3 installed at an electronic reference point (GPS continuous observation station).
The receiving device 302 that receives the positioning information from the GPS satellite 200 with high precision via 01, and the transmitting device 304 that transmits the positioning information received by this receiving device 302 via the antenna 303.
With.

Here, the receiving device 302 is an electronic device including the above-described atomic oscillator 1 of the present invention as its reference frequency oscillation source. Such a receiving device 302 has excellent reliability. Further, the positioning information received by the receiving device 302 is transmitted by the transmitting device 304 in real time.

The GPS receiving device 400 includes a satellite receiving unit 402 that receives positioning information from a GPS satellite 200 via an antenna 401 and a base station receiving unit 404 that receives positioning information from a base station device 300 via an antenna 403. Prepare

According to the positioning system 100 as described above, it is possible to make the atomic oscillator 1 which is a type of quantum interference device excellent in frequency characteristics and downsize.

3. Moving Object FIG. 12 is a diagram showing an embodiment of a moving object of the present invention.

In this figure, a moving body 1500 has a vehicle body 1501 and four wheels 1502, and is configured to rotate the wheels 1502 by a power source (engine) (not shown) provided in the vehicle body 1501. The atomic oscillator 1 is built in such a moving body 1500.

According to the moving body 1500 described above, the atomic oscillator 1 which is a kind of quantum interference device
It is possible to achieve miniaturization while improving the frequency characteristics of.

The electronic device including the atomic oscillator (quantum interference device) of the present invention is not limited to the above-mentioned ones, and examples thereof include a smartphone, a tablet terminal, a clock, a mobile phone, a digital still camera, and an inkjet ejection device (for example, an inkjet printer). ), Personal computer (mobile personal computer, laptop personal computer), TV, video camera, video tape recorder, car navigation device, pager, electronic notebook (including communication function), electronic dictionary, calculator, electronic game device , Word processors, workstations, video phones, crime prevention TV monitors, electronic binoculars, POS terminals, medical devices (eg electronic thermometers, blood pressure monitors, blood glucose meters, electrocardiogram measurement devices, ultrasonic diagnostic devices, electronic endoscopes), fish Detector, various measuring instruments, gages (e.g., gages for vehicles, aircraft, and ships), a flight simulator, terrestrial digital broadcasting, can be applied to a mobile phone base station or the like.

Although the quantum interference device, atomic oscillator, electronic device, and moving body of the present invention have been described above based on the illustrated embodiments, the present invention is not limited to these.

Further, in the quantum interference device, the atomic oscillator, the electronic device and the moving body of the present invention, the configuration of each part is
It can be replaced with an arbitrary configuration that exhibits a similar function, or an arbitrary configuration can be added.

Further, the quantum interference device, the atomic oscillator, the electronic device, and the moving body of the present invention may be formed by combining arbitrary configurations of the above-described embodiments.
In the above-described embodiment, an example in which the atomic oscillator of the present invention is applied to the atomic oscillator utilizing the quantum interference effect has been described, but the atomic oscillator of the present invention is also applied to an atomic oscillator utilizing the double resonance phenomenon. It is possible. In this case, the microwave signal applied to the alkali metal atoms may be generated using the microwave signal generated by the multiplication / combination unit.

1 ... Atomic oscillator, 1A ... Atomic oscillator, 2 ... Quantum interference unit, 5 ... Frequency conversion unit, 10 ...
Circuit part, 10A ... Circuit part, 21 ... Atomic cell, 22 ... Light source, 23 ... Photodetector, 31 ... Amplifier, 32 ... Detection circuit, 33 ... Modulation circuit, 34 ... Low frequency oscillator, 35 ... Driving circuit, 41 ... Detection circuit, 42 ... Voltage control type crystal oscillator, 43 ... Multiplying synthesis section, 43A ... Multiplying synthesis section, 44 ... Oscillator, 45 ... Divider, 51 ... Fourier transform circuit, 100 ... Positioning system, 200 ... GPS
Satellite, 300 ... Base station device, 301 ... Antenna, 302 ... Receiving device, 303 ... Antenna,
304 ... Transmitting device, 400 ... GPS receiving device, 401 ... Antenna, 402 ... Satellite receiving unit,
403 ... Antenna, 404 ... Base station receiving section, 411 ... Phase detector, 412 ... Low pass filter, 431 ... Fractional phase synchronization circuit, 432 ... Control section, 433 ... Modulation circuit, 4
34 ... Phase synchronization circuit, 1500 ... Moving body, 1501 ... Vehicle body, 1502 ... Wheels, A ... Range,
B ... range, C ... range, N ... number of changes, T ... period, a ... solid line, b ... chain line, f ... frequency,
f ₀ ... Frequency, fa ... Frequency, fb ... Frequency, ΔE ... Energy difference, Δf ... Amplitude, ω ₀ ...
Frequency, ω ₁ ... frequency, ω ₂ ... frequency

Claims (6)

An atomic cell containing alkali metal atoms,
A light source unit that emits light for exciting the alkali metal atom,
A photodetector that outputs a signal according to the intensity of light that has passed through the atomic cell,
A voltage-controlled oscillator that outputs a signal of a frequency according to the voltage signal,
Oscillator,
A signal from the voltage-controlled oscillator is frequency-multiplied to a frequency according to the transition frequency between the ground levels of the alkali metal atoms, and phase-modulated using digital processing based on the signal from the oscillator, A multiplication / combination unit that generates a microwave signal having a frequency component that changes stepwise;
A drive circuit for controlling the light source unit using the microwave signal;
Using digital processing, and the optical signal from the detector, the phase frequency converter for a frequency component frequency and outputs the frequency-converted signal to the side higher in accordance with the frequency of the modulation,
The signals from the frequency conversion unit detects by using a signal from the oscillator, and a detection unit which outputs the voltage signal according to the detection result, Ru with a quantum interference device. An atomic cell containing alkali metal atoms,
A light source unit that emits light for exciting the alkali metal atom,
A photodetector that outputs a signal according to the intensity of light that has passed through the atomic cell,
A voltage-controlled oscillator that outputs a signal of a frequency according to the voltage signal,
Oscillator,
A frequency divider that frequency-divides the signal from the oscillator;
The signal from the voltage-controlled oscillator, as well as frequency multiplication in a frequency corresponding to the transition frequency between the ground level of the alkali metal atoms, and position phase modulation using signals from previous SL divider, A multiplication and synthesis unit that generates a microwave signal,
A drive circuit for controlling the light source unit using the microwave signal;
By using digital processing, a signal from the photodetector, a frequency conversion unit that outputs a frequency-converted signal to a side where the frequency component corresponding to the frequency of the phase modulation has a higher frequency,
And a detection unit for detecting by using the signal from the previous SL oscillator signal from the frequency conversion unit, quantum interference device. The frequency conversion unit, quantum interference device according to claim 1 or 2 having a Fourier transform circuit. The frequency conversion unit, quantum interference device according to any one of claims 1 to 3 for converting a frequency of a detection subject to the signal at the detection unit to frequencies below 1kHz or 100 MHz. Claims 1 comprises a quantum interference device according to any one of 4, atomic oscillator. Comprising a quantum interference device according to any one of claims 1 to 5, electronic apparatus.

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