Time synchronization system

Abstract

To solve the problem in the case that a frequency stability of a whole time synchronization system is deteriorated in accordance with a time degradation of the oscillator even if a statistical processing is performed in an oscillator contained in a time synchronization system.SOLUTION: A time synchronization system 1 comprises: a plurality of synchronization sources 100 that outputs time information respectively; and an arithmetic part 200 that executes a predetermined processing to each time information to be output from the plurality of synchronization sources 100. The plurality of synchronization sources 100 comprises: an oscillator 30; and a detection part 40 that outputs fluctuation information of the oscillator 30. The arithmetic part 200 changes a predetermined processing executed to each time information on the basis of the fluctuation information to be output from the detection part 40 of each of the plurality of synchronization sources 100.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a time synchronization system.

Background Art

[0002] Conventionally, a time synchronization system is known that includes a plurality of synchronization sources each having an oscillator and outputting time information, and an arithmetic unit that executes predetermined processing on each time information output from the plurality of synchronization sources connected on a network. For example, Patent Document 1 discloses a time synchronization network in which a plurality of communication devices having synchronization sources such as a crystal oscillator and an atomic clock are connected, and time information is corrected by offset processing of time difference information between the communication devices.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, the oscillator of the synchronization source has a limited lifespan and deteriorates over time. In the time synchronization network disclosed in Patent Document 1, time information is corrected by performing offset processing. However, when the oscillator deteriorates over time, the frequency stability decreases and the correction accuracy decreases. Thus, in the conventional time synchronization system, due to the deterioration of the oscillator over time, etc., the frequency stability may decrease when viewed from the entire time synchronization system even if statistical processing is performed.

Means for Solving the Problems

[0005] The time synchronization system of the present invention for solving the above problems includes a plurality of synchronization sources each outputting time information, and an arithmetic unit that executes a predetermined process on each of the time information output from the plurality of synchronization sources. The time synchronization system is characterized in that each of the plurality of synchronization sources includes an oscillator and a detection unit that outputs variation information of the oscillator, and the arithmetic unit changes the predetermined process executed on the time information based on the variation information output from each of the detection units of the plurality of synchronization sources.

Brief Description of the Drawings

[0006]

Figure 1

Figure 2

Figure 3

Modes for Carrying Out the Invention

[0007] First, the present invention will be briefly described. The time synchronization system according to the first aspect of the present invention for solving the above problems includes a plurality of synchronization sources each outputting time information, and an arithmetic unit that executes a predetermined process on each of the time information output from the plurality of synchronization sources. The time synchronization system is characterized in that each of the plurality of synchronization sources includes an oscillator and a detection unit that outputs variation information of the oscillator, and the arithmetic unit changes the predetermined process executed on the time information based on the variation information output from each of the detection units of the plurality of synchronization sources.

[0008] According to this aspect, a plurality of synchronization sources and a calculation unit are provided. Each synchronization source includes an oscillator and a detection unit that outputs variation information of the oscillator. The calculation unit changes a predetermined process executed on the time information based on the variation information output from the detection unit of each synchronization source. That is, by providing a detection unit that outputs variation information of the oscillator, it is possible to detect the deterioration of the oscillator over time. Therefore, when the deterioration of the oscillator over time is detected, a predetermined process can be changed based on that information, so that a decrease in frequency stability in the entire time synchronization system can be suppressed.

[0009] The time synchronization system according to the second aspect of the present invention is an aspect subordinate to the first aspect, characterized in that the variation information includes at least one of information regarding intensity variation of a resonance signal of the oscillator and information regarding environmental variation around the synchronization source.

[0010] According to this aspect, the variation information includes at least one of information regarding intensity variation of a resonance signal of the oscillator and information regarding environmental variation around the synchronization source. Although the intensity variation of the resonance signal of the oscillator and the environmental variation around it lead to a decrease in frequency stability, by changing a predetermined process executed on the time information based on this information, a decrease in frequency stability in the entire time synchronization system can be suppressed.

[0011] The time synchronization system according to the third aspect of the present invention is an aspect subordinate to the first or second aspect, characterized in that the predetermined process is a statistical process on the time information output from each of the plurality of synchronization sources.

[0012] According to this aspect, the predetermined process is a statistical process on the time information output from each of the plurality of synchronization sources. Therefore, a statistical process on the time information output from each synchronization source can be executed with high accuracy.

[0013] The time synchronization system according to the fourth aspect of the present invention is an aspect subordinate to the third aspect, characterized in that the arithmetic unit changes the weighting in the statistical processing of the time information output from the corresponding synchronization source based on the variation information.

[0014] According to this aspect, the arithmetic unit changes the weighting in the statistical processing of the time information output from the corresponding synchronization source based on the variation information. Therefore, by increasing the weighting of highly reliable time information and decreasing the weighting of less reliable time information, a predetermined process can be suitably executed.

[0015] The time synchronization system according to the fifth aspect of the present invention is an aspect subordinate to the first or second aspect, characterized in that the oscillator is an atomic oscillator.

[0016] According to this aspect, the oscillator is an atomic oscillator capable of outputting a clock signal with high frequency accuracy using the energy transition of an atom. Therefore, in a time synchronization system including an atomic oscillator that requires high accuracy as an oscillator, a decrease in frequency stability when viewed from the entire time synchronization system can be suppressed.

[0017] [Example 1] Hereinafter, with reference to the accompanying drawings, the time synchronization system 1 according to the embodiment of the present invention will be described. First, with reference to FIGS. 1 and 2, the time synchronization system 1A according to Example 1 of the present invention will be described. FIG. 1 is a diagram showing the time synchronization system 1A of this embodiment. As shown in FIG. 1, the time synchronization system 1A of this embodiment includes a plurality of synchronization sources 100 each having an oscillator 30 and outputting time information, and an arithmetic unit 200 that executes ensemble statistical processing as a predetermined process on each time information output from these plurality of synchronization sources 100 connected on a wired or wireless network, and a storage unit 50 that stores various information, and is a time synchronization system 1.

[0018] As shown in FIG. 1, each of the plurality of synchronization sources 100 includes an oscillator 30 and a detection unit 40 that outputs variation information of the oscillator 30. Here, based on the variation information output from the respective detection units 40 of the plurality of synchronization sources 100, the arithmetic unit 40 can change a predetermined process to be executed on the time information. In other words, the time synchronization system 1A of the present embodiment can detect the deterioration over time of the oscillator 30 by including the detection unit 40 that outputs the variation information of the oscillator 30. Therefore, when the deterioration over time of the oscillator 30 is detected, a predetermined process can be changed based on the information, so that a decrease in frequency stability when viewed from the entire time synchronization system 1 can be suppressed.

[0019] Here, in the time synchronization system 1A of the present embodiment, as described above, the oscillator 30 is an atomic oscillator. Therefore, the time synchronization system 1A of the present embodiment can suppress a decrease in frequency stability when viewed from the entire time synchronization system 1 in a time synchronization system 1 including an atomic oscillator that requires high accuracy as the oscillator 30.

[0020] Hereinafter, the oscillator 30 and the detection unit 40 will be described in more detail with reference to FIG. 2. The oscillator 30 of the present embodiment is an atomic oscillator that can output a clock signal with high frequency accuracy using the energy transition of atoms. FIG. 2 is a block diagram showing the electrical configuration of the oscillator 30 and the detection unit 40, and is a diagram showing a circuit block that captures the resonance signal intensity in the oscillator 30 of the synchronization source 100 of the time synchronization system 1A of the present embodiment.

[0021] As shown in FIG. 2, the oscillator 30 includes a light source 31 that is a light emitting unit that emits light, a gas cell 32, and a photodiode 33 that is a light receiving unit. Note that the light source 31 and the gas cell 32 have a lifespan and may deteriorate over time. When the light source 31 and the gas cell 32 deteriorate over time, the frequency stability is likely to decrease.

[0022] Furthermore, the oscillator 30 has a detection circuit 34 as a sweep result output unit that outputs a sweep result signal corresponding to the resonance signal obtained by frequency sweeping in the oscillator 30. Further, it has a crystal oscillator (voltage-controlled crystal oscillator: VCXO) 35 as a voltage-controlled oscillator (VCO), a phase circuit 36, a PLL (Phase Locked Loop) 37, and an oscillator 38.

[0023] As the light source 31, for example, a semiconductor laser or the like can be used. Inside the gas cell 32, for example, gaseous alkali metals such as rubidium, cesium, and sodium are enclosed. The photodiode 33 receives the light emitted from the light source 31 and transmitted through the gas cell 32, undergoes a photoelectric change, and outputs it as an electrical signal.

[0024] The crystal oscillator 35 is not particularly limited, and for example, a thermostatic crystal oscillator (OCXO), a temperature-compensated crystal oscillator (TCXO), etc. can be used. The detection circuit 34 has a function of outputting a sweep result signal corresponding to (corresponding to) the resonance signal (EIT signal) obtained by frequency sweeping in the oscillator 30.

[0025] Hereinafter, the sweep result signal generated by the oscillator 30 will be further described. Hereinafter, for ease of understanding, as an example, specific numerical values will be used to describe the frequency etc. of each signal. First, gaseous rubidium with an atomic resonance frequency ω 0 of 9.2 GHz is enclosed in the gas cell 32, and it is assumed that the oscillator 38 outputs a signal of 111 Hz.

[0026] The signal with a frequency of f output from the crystal oscillator 35 is modulated by the phase circuit 36 at a frequency of 111 Hz and by the PLL 37 at 4.1×10 7It is multiplied by a factor, that is, multiplied so that the frequency becomes 4.6 GHz, and output toward the light source 31. In this way, when frequency sweeping is performed with a signal having a frequency of 111 Hz, atomic resonance, that is, an electromagnetically induced transparency (EIT) phenomenon occurs at a predetermined timing in the gas cell 32, and an atomic resonance signal (EIT signal), which is a steep signal generated along with the EIT phenomenon, is generated.

[0027] When the atomic resonance does not occur, a signal having a frequency of 111 Hz is input from the photodiode 33 to the detection circuit 34. However, when the atomic resonance occurs, a signal having a frequency of 111 Hz is not input from the photodiode 33 to the detection circuit 34, and a signal having a frequency of 222 Hz, that is, a second harmonic signal with respect to 111 Hz, is input. The signal having a frequency of 222 Hz when this atomic resonance occurs is the sweep result signal, and the sweep result signal is output from the detection circuit 34 toward the detection unit 40 which is a second harmonic level detection unit.

[0028] The detection unit 40 includes a diode 41 and an analog-to-digital converter 42. The detection unit 40 inputs an analog value from the oscillator 30, converts it into a digital value, and outputs it to the arithmetic unit 200.

[0029] The detection circuit 34 performs control so that the amplitude of the signal having a frequency of 111 Hz input from the photodiode 33 to the detection circuit 34 becomes zero. That is, the detection circuit 34 performs control so that a signal having a frequency of 111 Hz is not input from the photodiode 33 to the detection circuit 34.

[0030] Here, an example of the second harmonic level detection process will be described. The following second harmonic level detection process is executed in the arithmetic unit 200. First, in each synchronization source 100, after 24 hours (one day) have elapsed since the power of the synchronization source 100 was turned on, the digital detection value output from the analog-to-digital converter 42 is stored in the storage unit 50. Next, the digital detection value output from the analog-to-digital converter 42 is acquired every day and compared with the digital detection value stored in the storage unit 50 to calculate the amount of change. Thereafter, the arithmetic unit 200 performs statistical processing of the times of the plurality of synchronization sources 100 based on the magnitude of the amount of change.

[0031] As described above, the fluctuation information of the oscillator 30 in the time synchronization system 1A of the present embodiment is information regarding the intensity fluctuation of the resonance signal of the oscillator 30. Thus, it is preferable that the fluctuation information includes information regarding the intensity fluctuation of the resonance signal of the oscillator 30. Although the intensity fluctuation of the resonance signal of the oscillator 30 leads to a decrease in frequency stability, by changing a predetermined process (ensemble statistical process based on the above-described second harmonic level detection process) performed on the time information based on the information regarding the intensity fluctuation of the resonance signal of the oscillator 30, it is possible to suppress a decrease in frequency stability when viewed in the entire time synchronization system 1.

[0032] Also, as described above, the predetermined process (ensemble statistical process based on the above-described second harmonic level detection process) in the time synchronization system 1A of the present embodiment is a statistical process for the time information output from each of the plurality of synchronization sources 100. Therefore, the time synchronization system 1A of the present embodiment can perform statistical processing for the time information output from each synchronization source 100 with high accuracy.

[0033] Here, the arithmetic unit 200 changes the weighting in the statistical processing of the time information output from the corresponding synchronization source 100 based on the variation information of the oscillator 30 in a predetermined process (ensemble statistical processing based on the above-described second harmonic level detection process). Specifically, the weighting of highly reliable time information is increased and the weighting of less reliable time information is decreased. By executing such processing, the predetermined process can be suitably executed.

[0034] An example of the weighting in the statistical processing of the time information will be described below. The time synchronization system 1A of the present embodiment executes a statistical processing mode in which the amount of change when compared with the digital detection value stored in the storage unit 50 is defined as the resonance signal variation amount, and the weighting of the synchronization source 100 is changed based on the resonance signal variation amount. Table 1 below summarizes the relationship between the resonance signal variation amount, the weighting of the synchronization source 100, and the statistical processing mode. However, the present invention is not limited to the weighting as shown below with respect to the weighting of the synchronization source 100 based on the resonance signal variation amount.

[0035]

Table 1

[0036] As shown in Table 1, the time synchronization system 1A of the present embodiment has a mode 1 in which the weighting of the synchronization source 100 is set to 0.8 when the resonance signal variation amount is 1% or more and less than 5%. Although omitted in Table 1, when the resonance signal variation amount is less than 1%, a mode 0 in which the weighting of the synchronization source 100 is set to 1 is used. Similarly, the time synchronization system 1A of the present embodiment has a mode 2 in which the weighting of the synchronization source 100 is set to 0.6 when the resonance signal variation amount is 5% or more and less than 10%, and a mode 3 in which the weighting of the synchronization source 100 is set to 0.4 when the resonance signal variation amount is 10% or more and less than 20%. On the other hand, the time synchronization system 1A of the present embodiment determines that the resonance signal variation amount is too large when the resonance signal variation amount is 20% or more, and sets the weighting to 0, that is, a mode 4 in which the information of the synchronization source 100 is not used.

[0037] [Embodiment 2] Next, the time synchronization system 1B of Example 2 will be described with reference to FIG. 3. Note that FIG. 3 is a figure corresponding to FIG. 1 in the time synchronization system 1A of Example 1. In FIG. 3, the constituent members common to the above-described Example 1 are denoted by the same reference numerals, and detailed descriptions thereof are omitted. Here, the time synchronization system 1B of the present embodiment has the same configuration as the time synchronization system 1A of Example 1 except for the parts described below. Therefore, except for the parts described below, the time synchronization system 1B of the present embodiment has the same features as the time synchronization system 1A of Example 1.

[0038] As shown in FIG. 3, the synchronization source 100 of the time synchronization system 1B of the present embodiment further includes an environment sensing block 60 with respect to the synchronization source 100 of the time synchronization system 1A of Example 1. Therefore, in addition to the ensemble statistical processing based on the resonance signal fluctuation amount executable in the time synchronization system 1A of Example 1, ensemble statistical processing can be executed based on the detection information detected by the environment sensing block 60. The environment sensing block 60 of the time synchronization system 1B of the present embodiment is configured to be able to detect the environment around the synchronization source 100. Specifically, it is configured to be able to detect the temperature of the area where the synchronization source 100 is located, the vibration of the area where the synchronization source 100 is located, the magnetic field of the area where the synchronization source 100 is located, the radiation of the area where the synchronization source 100 is located, and the like.

[0039] Therefore, the arithmetic unit 40 of the time synchronization system 1B of the present embodiment can change the predetermined processing to be executed on the time information based on the variation information output from each detection unit 40 of the plurality of synchronization sources 100. However, based on the information regarding the environmental variation around the synchronization source 100 as the variation information, the predetermined processing to be executed on the time information can be changed. Therefore, the time synchronization system 1B of the present embodiment can suppress a decrease in frequency stability when viewed from the entire time synchronization system 1 by changing the predetermined processing (ensemble statistical processing) to be executed on the time information based on the information regarding the environmental variation around the synchronization source 100.

[0040] Also, the time synchronization system 1B of this embodiment can change the weighting in the statistical processing for the time information output from each of the plurality of synchronization sources 100 based on the information regarding the environmental variations around the synchronization source 100. An example of the weighting in the statistical processing of the time information will be described below. The time synchronization system 1B of this embodiment executes a statistical processing mode in which the weighting of the synchronization source 100 is changed based on the amount of environmental variation consisting of the amount of temperature variation from the reference value (temperature one day ago), the amount of vibration variation from the reference value (0G), the amount of magnetic field variation from the reference value (0 Gauss), and the amount of radiation variation from the reference value (0 rad), which is the detection result of the environmental sensing block 60.

[0041] The relationships among the amount of environmental variation, the weighting of the synchronization source 100, and the statistical processing mode are summarized in Tables 2 to 5 below. Specifically, the relationship among the amount of temperature variation, the weighting of the synchronization source 100, and the statistical processing mode is summarized in Table 2 below, the relationship among the amount of vibration variation, the weighting of the synchronization source 100, and the statistical processing mode is summarized in Table 3 below, the relationship among the amount of magnetic field variation, the weighting of the synchronization source 100, and the statistical processing mode is summarized in Table 4 below, and the relationship among the amount of radiation variation, the weighting of the synchronization source 100, and the statistical processing mode is summarized in Table 5 below. However, the present invention is not limited to the weighting as shown below with respect to the weighting of the synchronization source 100 based on such an amount of environmental variation.

[0042]

Table 2

[0043] As shown in Table 2, the time synchronization system 1B of this embodiment sets Mode 1 with a weighting of 0.8 for the synchronization source 100 when the temperature fluctuation amount is 20°C or more and less than 40°C. Although omitted in Table 2, when the temperature fluctuation amount is less than 20°C, it is set as Mode 0 with a weighting of 1 for the synchronization source 100. Similarly, the time synchronization system 1B of this embodiment sets Mode 2 with a weighting of 0.6 for the synchronization source 100 when the temperature fluctuation amount is 40°C or more and less than 60°C, and sets Mode 3 with a weighting of 0.4 for the synchronization source 100 when the temperature fluctuation amount is 60°C or more and less than 80°C. On the other hand, when the temperature fluctuation amount of the time synchronization system 1B of this embodiment is 80°C or more, it is determined that the temperature fluctuation amount is too large, and the weighting is set to 0, that is, Mode 4 in which the information of the synchronization source 100 is not used.

[0044]

Table 3

[0045] As shown in Table 3, the time synchronization system 1B of this embodiment sets Mode 1 with a weighting of 0.8 for the synchronization source 100 when the vibration fluctuation amount is 0.001G or more and less than 0.01G (1G = 9.8m / s 2 ). Although omitted in Table 3, when the vibration fluctuation amount is less than 0.001G, it is set as Mode 0 with a weighting of 1 for the synchronization source 100. Similarly, the time synchronization system 1B of this embodiment sets Mode 2 with a weighting of 0.6 for the synchronization source 100 when the vibration fluctuation amount is 0.01G or more and less than 0.1G, and sets Mode 3 with a weighting of 0.4 for the synchronization source 100 when the vibration fluctuation amount is 0.1G or more and less than 1G. On the other hand, when the vibration fluctuation amount of the time synchronization system 1B of this embodiment is 1G or more, it is determined that the vibration fluctuation amount is too large, and the weighting is set to 0, that is, Mode 4 in which the information of the synchronization source 100 is not used.

[0046]

Table 4

[0047] As shown in Table 4, when the magnetic field fluctuation amount is 0.01 Gauss or more and less than 0.1 Gauss, the time synchronization system 1B of this embodiment is set to Mode 1 with a weighting of 0.8 for the synchronization source 100. Although omitted in Table 4, when the magnetic field fluctuation amount is less than 0.01 Gauss, it is set to Mode 0 with a weighting of 1 for the synchronization source 100. Similarly, when the magnetic field fluctuation amount is 0.1 Gauss or more and less than 1 Gauss, the time synchronization system 1B of this embodiment is set to Mode 2 with a weighting of 0.6 for the synchronization source 100, and when the magnetic field fluctuation amount is 1 Gauss or more and less than 10 Gauss, it is set to Mode 3 with a weighting of 0.4 for the synchronization source 100. On the other hand, when the magnetic field fluctuation amount is 10 Gauss or more, the time synchronization system 1B of this embodiment determines that the magnetic field fluctuation amount is too large and sets the weighting to 0, that is, Mode 4 in which the information of the synchronization source 100 is not used.

[0048]

Table 5

[0049] As shown in Table 5, when the radiation fluctuation amount is 10 rad or more and less than 100 rad (100 rad = 1 Gy), the time synchronization system 1B of this embodiment is set to Mode 1 with a weighting of 0.8 for the synchronization source 100. Although omitted in Table 5, when the radiation fluctuation amount is less than 10 rad, it is set to Mode 0 with a weighting of 1 for the synchronization source 100. Similarly, when the radiation fluctuation amount is 100 rad or more and less than 1000 rad, the time synchronization system 1B of this embodiment is set to Mode 2 with a weighting of 0.6 for the synchronization source 100, and when the radiation fluctuation amount is 1000 rad or more and less than 10000 rad, it is set to Mode 3 with a weighting of 0.4 for the synchronization source 100. On the other hand, when the radiation fluctuation amount is 10000 rad or more, the time synchronization system 1B of this embodiment determines that the vibration fluctuation amount is too large and sets the weighting to 0, that is, Mode 4 in which the information of the synchronization source 100 is not used.

[0050] The present invention is not limited to the above-described embodiments, and can be realized in various configurations without departing from the gist thereof. The technical features in the embodiments corresponding to the technical features in each form described in the summary of the invention can be appropriately replaced or combined in order to solve some or all of the above-described problems, or to achieve some or all of the above-described effects. Further, if the technical features are not described as essential in this specification, they can be appropriately deleted.

Description of Reference Numerals

[0051] 1... Time synchronization system, 1A... Time synchronization system, 1B... Time synchronization system, 30... Oscillator (atomic oscillator), 31... Light source, 32... Gas cell, 33... Photodiode, 34... Detection circuit, 35... Crystal oscillator, 36... Phase circuit, 37... PLL, 38... Oscillator, 40... Detection unit, 41... Diode, 42... Analog-to-digital converter, 50... Storage unit, 60... Environment sensing block, 100... Synchronization source, 200... Arithmetic unit

Claims

1. A time synchronization system comprising: a plurality of synchronization sources each outputting time information; and a calculation unit that executes a predetermined process on each of the time information output from the plurality of synchronization sources, each of the plurality of synchronization sources includes an oscillator and a detection unit that outputs fluctuation information of the oscillator; A time synchronization system characterized in that the calculation unit changes the specified processing to be performed on the time information based on the fluctuation information output from the detection unit of each of the multiple synchronization sources.

2. 2. The time synchronization system according to claim 1, A time synchronization system, characterized in that the fluctuation information includes at least one of information regarding fluctuations in intensity of the resonance signal of the oscillator and information regarding environmental fluctuations surrounding the synchronization source.

3. 3. The time synchronization system according to claim 1, A time synchronization system, wherein the predetermined processing is a statistical processing of the time information output from each of the plurality of synchronization sources.

4. 4. The time synchronization system according to claim 3, A time synchronization system characterized in that the calculation unit changes a weighting in the statistical processing of the time information output from the corresponding synchronization source based on the fluctuation information.

5. 3. The time synchronization system according to claim 1, A time synchronization system, wherein the oscillator is an atomic oscillator.

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