High-precision time stability measuring method and device

Abstract

The invention discloses a high-precision time stability measurement method, which is used for measuring time stability between a head node and a tail node of a synchronous network, and comprises the following steps: measuring frequency stability between the head node and the tail node of the synchronous network; determining a proportional relation between the time stability TDEV and the frequency stability ADEV under a set sampling interval and integral time condition; and obtaining a time stability index according to the proportional relation and the measured frequency stability. The invention also comprises a device for realizing the high-precision time stability measurement method. According to the invention, the problem of low measurement precision of the TDEV is solved.

Description

Technical Field

[0001] The present application relates to the field of time synchronization technology, and in particular to a high-precision time stability measurement method and device. Background Art

[0002] In the currently commonly used time transfer network, the time signal is transmitted through the IEEE 1588 protocol or the optical fiber timing technology, and then the 1PPS signal is output at each transmission node. In order to evaluate the quality of the time transfer performance of the network, the relative time deviation between the network nodes is usually measured, and the TDEV (Time Deviation) index is calculated. The current time deviation measurement is measured by a time interval analyzer, and the error of the time interval analyzer is relatively large. In order to improve the time deviation measurement accuracy, the present invention explores a method for improving the measurement accuracy of TDEV by improving the frequency measurement accuracy. Summary of the invention

[0003] The present application proposes a high-precision time stability measurement method and device to solve the problem of low measurement accuracy of TDEV.

[0004] In a first aspect, an embodiment of the present application provides a high-precision time stability measurement method for measuring the time stability between the first and last nodes of a synchronization network, comprising the following steps:

[0005] Measure the frequency stability between the first and last nodes of the synchronization network;

[0006] Under the conditions of set sampling interval and integration time, determine the proportional relationship between time stability TDEV and frequency stability ADEV;

[0007] According to the proportional relationship and the measured frequency stability, a time stability index is obtained.

[0008] In an embodiment of the present application, the measurement error of the time stability is converted into a frequency error, which is greater than the measurement error of the frequency stability.

[0009] In an embodiment of the present application, the degree to which the proportional relationship changes over time is less than a set threshold.

[0010] In the embodiment of the present application, the proportional relationship takes a constant.

[0011] In an embodiment of the present application, the measurement error increment introduced by the proportional relationship changing over time is smaller than the measurement error increment of the frequency stability when the measurement error of the time stability is converted into a frequency error.

[0012] In the embodiment of the present application, for the 1PPS signal, the proportional relationship is as shown in formula (7), and the theoretical value of the proportional relationship is a constant.

[0013] In an embodiment of the present application, a frequency signal having the same source as the time signal to be measured is selected, and a frequency stability measuring instrument is used to measure the second-level ADEV of the frequency signal.

[0014] In the second aspect, the present application also proposes a high-precision time stability measurement device for implementing the method described in any embodiment of the first aspect of the present application, including an acquisition module, a determination module, and a generation module.

[0015] The acquisition module is used to measure the frequency stability between the first and last nodes of the synchronization network;

[0016] The determination module is used to determine the proportional relationship between the time stability TDEV and the frequency stability ADEV under the set sampling interval and integration time conditions;

[0017] The generating module obtains a time stability index according to the proportional relationship and the measured frequency stability.

[0018] An embodiment of the present application further provides a computer-readable storage medium having a computer program stored thereon, wherein when the program is executed by a processor, the method described in any embodiment of the first aspect of the present application is implemented.

[0019] An embodiment of the present application also proposes an electronic device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements a method as described in any embodiment of the first aspect of the present application when executing the computer program.

[0020] At least one of the above technical solutions adopted in the embodiments of the present application can achieve the following beneficial effects: reducing the measurement error of the time stability (TDEV) obtained by time measurement; providing an alternative time stability measurement method when the device has no 1PPS output signal. In particular, the present invention utilizes the proportional relationship between TDEV and ADEV and proposes a method of replacing the time stability measurement with a more accurate frequency stability measurement: in particular, the unique proportional relationship at the second-level stability. The present application improves the measurement accuracy of the second-level time stability (TDEV) obtained by time measurement. When the device has no 1PPS time signal output, a method of replacing the time stability measurement with a frequency stability measurement is provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0022] Figure 1This is the 1PPS time deviation measurement topology diagram;

[0023] Figure 2 This is a flowchart for implementing the application method;

[0024] Figure 3 This is the topology diagram for 10MHz frequency deviation measurement;

[0025] Figure 4 A schematic diagram of the device of this application;

[0026] Figure 5 It is the measurement value of 1PPS time interval;

[0027] Figure 6 The sampling frequency accuracy is 1s. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solution and advantages of the present application clearer, the technical solution of the present application will be clearly and completely described below in combination with the specific embodiments of the present application and the corresponding drawings. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present application.

[0029] The key technical point of this application is to replace the time stability (TDEV) measurement with a higher-precision frequency stability (Allan variance) measurement. The core of the technical solution claimed in this application is to replace the time stability (TDEV) measurement with a higher-precision frequency stability (Allan variance) measurement.

[0030] The technical solutions provided by various embodiments of the present application are described in detail below in conjunction with the accompanying drawings.

[0031] Figure 1 This is the 1PPS time deviation measurement topology diagram. Figure 1 As shown, the signal source outputs 1PPS and 10MHz signals to the synchronous network equipment and test instrument. The time information of the signal source is transmitted through the synchronous network and returned to the test instrument. The instrument measures the relative time deviation of the 1PPS output by the first and last nodes as the time transmission accuracy of the network.

[0032] The TDEV formula is shown in formula (1):

[0033]

[0034] Where:

[0035] x i ——Phase sampling data;

[0036] τ0——the time interval between adjacent samples;

[0037] n——the number of samples within the integration time;

[0038] τ=nτ0——integration time.

[0039] x in the TDEV formula i That is Figure 1 The difference between the first and last nodes 1PPS, {x i By substituting the sequence into formula (1), we can get the time stability TDEV index of the time transfer network. For 1PPS signal, we usually pay more attention to the time stability at the second level, that is, the performance TDEV(@1s) when n=τ0=1 in the formula.

[0040] Since x in the usual TDEV formula i The time stability is measured by measuring the time interval of 1PPS with a time interval analyzer. Through analysis, it is found that the time measurement function of the time interval analyzer has a certain measurement error. For example, the time interval measurement accuracy of SR620 is 25ps. Since the error caused by measurement accuracy is usually evenly distributed, the impact of measurement accuracy on the measurement result is 10.2ps. The sampling time interval is 1s, which is converted to a frequency error of 1.0×10 -11 , which is far less accurate than what can be achieved by direct frequency measurement.

[0041] Figure 2 This is an implementation flow chart of the method of the present application. The embodiment of the present application proposes a high-precision time stability measurement method for measuring the time stability between the first and last nodes of a synchronization network, including the following steps 10 to 30.

[0042] Step 10: Measure the frequency stability between the first and last nodes of the synchronization network.

[0043] In an embodiment of the present application, a frequency signal homologous to the measured time signal is selected, and a frequency stability measuring instrument is used to measure the second-level ADEV of the frequency signal. Preferably, a frequency signal homologous to the time signal, such as a 10 MHz signal, is selected, and a frequency stability measuring instrument of the prior art is used to measure the second-level ADEV of the 10 MHz signal.

[0044] The reason for directly performing the frequency stability measurement is as described above. In the embodiment of the present application, the measurement error of the time stability is converted into a frequency error, which is greater than the frequency stability measurement error.

[0045] The measurement result expression of the relative time deviation of the first and last nodes 1PPS tested by the time interval test instrument is shown in formula (2):

[0046] ΔT=σ+δ (2)

[0047] Where σ represents the noise of network time-frequency transmission, that is, the actual 1PPS time deviation output by the network's first and last stations, and δ represents the noise introduced by the test instrument.

[0048] The noise introduced by the instrument mainly includes the error introduced by the measurement reference source and the error introduced by the measurement accuracy. The reference source uses the 10MHz signal of the signal source as an external reference, so it is the same source as the two measured 1PPS signals, so this factor can be approximately ignored. Measurement accuracy is an inherent measurement influencing factor of the instrument. For example, the measurement accuracy of the time interval analyzer SR620 is 25ps, so each measurement value contains a measurement error of 25ps. Since the influence of measurement accuracy on the measurement result is random, it is usually evenly distributed in the range of 0ps to 25ps, so x i The measurement error is

[0049]

[0050] According to the TDEV formula (1), x i+n -x i , including the first and last time interval measurements, so the error introduced by the instrument The sampling time interval is 1s, and the error of frequency measurement is 1.0×10 -11 @1s.

[0051] Since the frequency measurement is more accurate than the simple phase measurement, the frequency measurement accuracy can reach at least 1.0×10 -14 Therefore, the measurement error of the time stability converted into a frequency error is much larger than the measurement error of the frequency stability. In other words, the measurement error of the frequency stability is much smaller than the measurement error of the time stability converted into a frequency error. At present, the measurement accuracy of frequency stability (Allan variance, ADEV) can reach a very high level, such as 1.0×10 -15 Magnitude.

[0052] Step 20: Under the set sampling interval and integration time conditions, determine the proportional relationship between the time stability TDEV and the frequency stability ADEV.

[0053] Those skilled in the art know that the expression of TDEV is as shown in formula (1);

[0054] ADEV is:

[0055]

[0056] Therefore, according to formula (1) and formula (4), the ratio R of TDEV and ADEV can be obtained. It can be understood that, except for special set sampling interval and integration time conditions, the ratio of TDEV and ADEV is generally not a constant, but a value that changes with time.

[0057] Numerical analysis shows that the proportional relationship R between the two is distributed within a range. In the embodiment of the present application, the degree to which the proportional relationship changes over time is limited to be less than a set threshold.

[0058] In one embodiment of the present application, the proportional relationship may be a constant R0. When the proportional relationship between the two changes randomly over time, a constant, such as a mean value or a root mean square value, may be obtained by statistical means.

[0059] It can be understood that the random change of the proportional relationship leads to errors when converting from ADEV to TDEV. Considering that the measurement of ADEV has significant performance advantages over the measurement of TDEV, the uncertainty caused by the change of the proportional relationship can be tolerated within a certain range. In an embodiment of the present application, the measurement error increment introduced by the change of the proportional relationship over time is limited to be less than the increment of the frequency stability measurement error when the measurement error of the time stability is converted into a frequency error.

[0060] Since the 1PPS time signal is directly taken from the phase of the frequency signal at seconds, the stability of the 1PPS signal is consistent with the stability of the frequency signal. If the relationship between the frequency stability and the time stability is found, the time measurement is achieved by frequency measurement, which will greatly improve the measurement accuracy of the 1PPS time stability. In an embodiment of the present application, for the 1PPS signal, the proportional relationship is taken as formula (7), and the proportional relationship is a constant at this time.

[0061] Step 30: According to the proportional relationship and the measured frequency stability, a time stability index is obtained, that is, TDEV=R×ADEV, or TDEV=R0×ADEV.

[0062] Therefore, the conversion relationship between TDEV and ADEV can improve the measurement accuracy of 1PPS TDEV (1s). We analyzed the difference between TDEV and ADEV in 1s stability. The relationship of times is as shown in formula (7). Formula (7) is used to calculate the second-level measurement value of time TDEV.

[0063] The specific proof process is as follows:

[0064] For the TDEV(1s) indicator, n = 1, τ0 = 1, then

[0065]

[0066] For the ADEV(1s) indicator, τ = 1 sampling interval, then

[0067]

[0068] According to equations (5) and (6), at 1s stability

[0069]

[0070] Therefore, by measuring the ADEV value of the frequency signal at the second level stability, the TDEV of the time signal can be obtained. Based on the above analysis, the present invention proposes a method of using the homologous frequency signal stability (Allan variance) measurement to replace the 1PPS time stability (TDEV) measurement.

[0071] Therefore, the present invention proposes a high-precision time stability (TDEV) measurement method that uses frequency measurement instead of time measurement, and measures the frequency stability (ADEV@1s) of a frequency signal (such as 10MHz) homologous to the measured 1PPS to replace the 1PPS time stability (TDEV@1s). This will greatly improve the measurement accuracy of the 1PPS time stability and provide an alternative time stability measurement method when the device does not have a 1PPS output interface.

[0072] Figure 3 This is the topology diagram for measuring the 10MHz frequency deviation. The test method flow is as follows:

[0073] Select a frequency signal that is the same as the time signal being measured, such as a 10MHz signal;

[0074] Use the existing frequency stability measurement instrument to measure the second-level ADEV of the 10MHz signal. The test topology is as follows: Figure 3 As shown in the figure, the principle of high-precision frequency measurement is usually achieved by frequency difference multiplication method. Taking a 10MHz signal as an example, assuming that the measured signal frequency is 10MHz+Δf, Δf is the frequency deviation, the measurement steps are as follows:

[0075] Mix 9.999MHz with 10MHz+Δf signal to get 1kHz+Δf;

[0076] The mixed signal is multiplied by M, assuming that M is 10000, to obtain 10MHz+MΔf;

[0077] Mix 9.999MHz with 10MHz+Δf signal to get 1kHz+MΔf;

[0078] The sampling time is 1s. If the measurement resolution is 0.001Hz, it can be assumed that the frequency after mixing is 1.000002kHz.

[0079] The measurement accuracy can be obtained by calculation 2×10 -14 <<1.0×10 -11 , so the accuracy of the frequency measurement method is higher than that of the time measurement.

[0080] Finally, using formula (7), the second-level measurement value of time TDEV is calculated.

[0081] Figure 4 The present application provides a schematic diagram of a high-precision time stability measurement device, which is used to implement the method described in any one of the embodiments of the first aspect of the present application, including an acquisition module 41, a determination module 42, and a generation module 43.

[0082] The acquisition module is used to measure the frequency stability between the first and last nodes of the synchronization network, such as step 10, Figure 3 Test configuration shown.

[0083] The determination module is used to determine the proportional relationship R, or R0, between the time stability TDEV and the frequency stability ADEV under the set sampling interval and integration time conditions, such as the function described in step 20 of the embodiment of the present application.

[0084] The generation module obtains a time stability index according to the proportional relationship and the measured frequency stability, such as the function described in step 30 of the embodiment of the present application.

[0085] Figure 5 is the 1PPS time interval measurement value. We constructed the time signal noise to verify the method mentioned in the present invention. The original signal is as follows: Figure 5 As shown in the figure, the TDEV value is 7.8149×10 -12 @1s. Formula (6) can be further transformed to obtain formula (8)

[0086]

[0087] where y t Represents the frequency value within τ time. Figure 5 The measured value in is converted into the frequency accuracy of 1s sampling period, such as Figure 6 The figure shows the 1s sampling frequency accuracy. The Allan variance ADEV calculated by formula (8) is 1.3536×10 -11 @1s. By calculation It is proved that formula (7) is correct, so the TDEV of the time signal can be obtained by measuring the ADEV value of the frequency signal at the second-level stability.

[0088] It should be noted that the execution subject of each step of the method provided in the embodiment of the present application can be the same device, or the method can be executed by different devices. For example, the execution subject of step 10 and step 20 can be device 1, and the execution subject of step 30 can be device 2; for another example, the execution subject of step 10 can be device 1, and the execution subject of step 20 and step 30 can be device 2; and so on.

[0089] Those skilled in the art will appreciate that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0090] Therefore, the present application also proposes a computer-readable storage medium on which a computer program is stored. When the program is executed by a processor, the method described in any embodiment of the present application is implemented.

[0091] Furthermore, the present application also proposes an electronic device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the method described in any embodiment of the present application when executing the computer program.

[0092] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0093] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0094] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process in the computer or other programmable device. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0095] In a typical configuration, a computing device includes one or more processors (CPU), input / output interfaces, network interfaces, and memory. The memory may include non-permanent storage in a computer-readable medium, random access memory (RAM) and / or non-volatile memory in the form of read-only memory (ROM) or flash RAM. Memory is an example of a computer-readable medium.

[0096] It should also be noted that the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, commodity or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, commodity or device. In the absence of more restrictions, the elements defined by the sentence "comprises a ..." do not exclude the existence of other identical elements in the process, method, commodity or device including the elements.

[0097] The above is only an embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the scope of the claims of the present application.

Claims

1. A high-precision time stability measurement method for measuring the time stability between the first and last nodes of a synchronization network, characterized in that: The following steps are involved: Measure the frequency stability between the first and last nodes of the synchronization network; Under the conditions of set sampling interval and integration time, determine the proportional relationship between time stability TDEV and frequency stability ADEV; According to the proportional relationship and the measured frequency stability, a time stability index is obtained.

2. The high-precision time stability measurement method according to claim 1, characterized in that: The measurement error of the time stability is converted into a frequency error, which is greater than the measurement error of the frequency stability.

3. The high-precision time stability measurement method according to claim 1, characterized in that: The degree to which the proportional relationship changes over time is less than a set threshold.

4. The high-precision time stability measurement method according to claim 1, characterized in that: The proportional relationship takes a constant.

5. The high-precision time stability measurement method according to claim 1, characterized in that: The measurement error increment introduced by the proportional relationship changing with time is smaller than the measurement error increment of the frequency stability when the measurement error of the time stability is converted into a frequency error.

6. The high-precision time stability measurement method according to claim 1, characterized in that: For 1PPS signal, the proportional relationship is: Among them, τ0 is the time interval between adjacent sample values; n is the number of samples within the integration time; τ = nτ0 is the integration time.

7. The high-precision time stability measurement method according to claim 1, characterized in that: Select a frequency signal with the same source as the time signal to be measured, and use a frequency stability measuring instrument to measure the second-level ADEV of the frequency signal.

8. A high-precision time stability measurement device, used to implement the method according to any one of claims 1 to 7, characterized in that: It includes acquisition module, determination module and generation module; The acquisition module is used to measure the frequency stability between the first and last nodes of the synchronization network; The determination module is used to determine the proportional relationship between the time stability TDEV and the frequency stability ADEV under the set sampling interval and integration time conditions; The generating module obtains a time stability index according to the proportional relationship and the measured frequency stability.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the program is executed by a processor, the method according to any one of claims 1 to 7 is implemented.

10. An electronic device comprising a memory, a processor and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the computer program, the method according to any one of claims 1 to 7 is implemented.

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