Phase error estimation method, phase error compensation method and DAS system

Abstract

The invention provides a phase error estimation method, a phase error compensation method and a DAS system, and the method comprises the steps: obtaining a reference frame of a to-be-measured signal and a to-be-measured frame; performing cross-correlation calculation on the reference frame and the to-be-detected frame, and determining an initial time delay; at least three groups of time offset-cross-correlation calculation values are used for fitting, and a mapping function used for representing the relation between the time offset and the cross-correlation calculation values is obtained; obtaining correction time delay; and correcting the initial time delay by using the correction time delay to obtain total time delay and a phase error corresponding to the total time delay. According to the scheme, fitting is carried out by utilizing at least three groups of time offset-cross-correlation calculation values, so that the mapping function used for representing the relationship between the time offset and the cross-correlation calculation values is obtained, the correction time delay is further obtained, then the initial time delay is corrected by utilizing the correction time delay, and the time delay correction accuracy is improved. And the phase error estimation accuracy of the phase error estimation method can be improved.

Description

Technical Field

[0001] The present application relates to the field of sensor technology, and in particular to a phase error estimation method, a phase error compensation method and a DAS system. Background Art

[0002] Pulse jitter refers to the tiny fluctuations or glitches caused by various reasons such as slight touch by human hands and oscillations generated by circuit hardware when the pulse signal is rising or falling. These fluctuations will cause the pulse waveform to be distorted.

[0003] When pulse jitter occurs, the pulse has a time deviation relative to the predetermined time. This causes an additional phase error to be introduced into each demodulation phase acquired in the Distributed Acoustic Sensing System (DAS), which eventually increases the demodulation phase error.

[0004] Regarding the phase error caused by pulse jitter, there is still much room for improvement in the phase error estimated by the phase error estimation scheme in the related art. Summary of the invention

[0005] The purpose of the embodiments of the present application is to provide a phase error estimation method, a phase error compensation method and a DAS system, so as to at least improve the accuracy of the phase error estimation value.

[0006] In a first aspect, an embodiment of the present application provides a phase error estimation method, the method comprising: obtaining a reference frame and a frame to be measured of a signal to be measured; performing cross-correlation calculation on the reference frame and the frame to be measured to determine an initial delay; wherein the initial delay is a time offset corresponding to a maximum value of the cross-correlation calculation; performing fitting using at least three sets of time offset-cross-correlation calculation values ​​to obtain a mapping function for characterizing the relationship between the time offset and the cross-correlation calculation value; obtaining a correction delay; wherein the correction delay is a time offset corresponding to a time when the derivative of the mapping function is zero; and correcting the initial delay using the correction delay to obtain a total delay and a phase error corresponding to the total delay.

[0007] In the implementation process of the above scheme, at least three groups of time offset-cross-correlation calculation values ​​are used for fitting, so as to obtain a mapping function for characterizing the relationship between the time offset and the cross-correlation calculation value, and then obtain the correction delay, and then use the correction delay to correct the initial delay, which is conducive to improving the phase error estimation accuracy of the above phase error estimation method. In particular, it is suitable for calculating the phase error caused by pulse jitter in the DAS system.

[0008] In an implementation of the first aspect, performing cross-correlation calculation on the reference frame and the frame to be tested to obtain an initial delay includes: obtaining a delay estimation result of the signal to be tested; wherein the delay estimation result is used to characterize the relationship between the total delay of the signal to be tested and the unit sampling duration; if the delay estimation result is that the total delay is not less than the unit sampling duration, performing cross-correlation calculation on the reference frame and the frame to be tested to determine the initial delay; performing fitting using at least three groups of the time offset-cross-correlation calculation values ​​to obtain the mapping function used to characterize the relationship between the time offset and the cross-correlation calculation value; obtaining the correction delay; and correcting the initial delay using the correction delay to obtain the phase error.

[0009] In the implementation process of the above scheme, the reference frame and the frame to be measured will be cross-correlated only when the delay estimation result is that the total delay is not less than the unit sampling duration, which can reduce a large amount of invalid calculations and is conducive to improving the execution efficiency of the above phase error estimation method.

[0010] In an implementation manner of the first aspect, performing cross-correlation calculation on the reference frame and the frame to be measured to obtain an initial delay includes:

[0011] Obtaining a delay estimation result of the signal to be tested; wherein the delay estimation result is used to characterize the relationship between the total delay of the signal to be tested and the unit sampling duration;

[0012] If the delay estimation result is that the total delay is less than the unit sampling duration, a reference subframe and at least three subframes to be tested are selected from the reference frame and the frame to be tested respectively; a mapping function for characterizing the relationship between the time offset and the cross-correlation calculation value is obtained based on the reference subframe and the subframe to be tested; and the correction delay is obtained based on the mapping function; wherein the reference subframe and the subframe to be tested contain the same number of sampling points, the reference subframe and the subframe to be tested are respectively composed of a group of continuous sampling points in the reference frame and the frame to be tested, and at least three subframes to be tested correspond to different time offsets.

[0013] In the implementation process of the above scheme, when the delay is less than the unit sampling time length, by fitting the mapping function and obtaining the correction delay by selecting the reference subframe and the subframe to be measured in the reference frame and the frame to be measured respectively, it is beneficial to further reduce the calculation amount of the above phase error estimation method, and thus help improve the execution efficiency of the above phase error estimation method.

[0014] In an implementation of the first aspect, the mapping function for characterizing the relationship between the time offset and the cross-correlation calculation value obtained based on the reference subframe and the subframe to be measured includes: performing dot product operations on the reference subframe and at least three of the subframes to be measured, respectively, to obtain at least three sets of time offset-cross-correlation calculation values.

[0015] In the implementation process of the above scheme, after obtaining the reference subframe and the subframe to be measured, the cross-correlation calculation value between the reference frame and the subframe to be measured can be directly obtained through the dot product operation between the reference subframe and the subframe to be measured, and then the mapping function is fitted through at least three groups of time offset-cross-correlation calculation values, which is beneficial to improve the execution efficiency of the above phase error estimation method.

[0016] In an implementation manner of the first aspect, selecting at least three subframes to be tested from the frame to be tested includes:

[0017] A first subframe to be tested is selected from the frame to be tested; wherein the index of the sampling points in the first subframe to be tested is the same as the index of the sampling points in the reference subframe.

[0018] In the implementation process of the above scheme, when fitting the mapping function, the cross-correlation calculation value without time offset is taken into account, so that the fitted mapping function is closer to the actual mapping relationship, thereby obtaining a more accurate correction delay, which is beneficial to improving the phase error estimation accuracy of the above phase error estimation method.

[0019] In an implementation manner of the first aspect, selecting at least three subframes to be tested from the frame to be tested includes:

[0020] A first subframe to be tested, a second subframe to be tested and a third subframe to be tested are selected from the frame to be tested; wherein the index of the sampling point in the first subframe to be tested is the same as the index of the sampling point in the reference subframe; the index of the sampling point in the second subframe to be tested and the index of the sampling point in the reference subframe are spaced forward by one unit sampling time length; the index of the sampling point in the third subframe to be tested and the index of the sampling point in the reference subframe are spaced backward by one unit sampling time length.

[0021] In the implementation process of the above scheme, three subframes to be measured, namely the first subframe to be measured, the second subframe to be measured and the third subframe to be measured, are selected to fit the mapping function. On the one hand, it is beneficial to improve the fitting effect of the mapping function, and thus improve the accuracy of the correction delay; on the other hand, it is beneficial to reduce the amount of invalid calculations and improve the estimation efficiency of the above phase error estimation method.

[0022] In an implementation manner of the first aspect, differences between the time offsets and the initial time delays in at least three groups of the time offset-cross-correlation calculation values ​​all meet a preset difference threshold requirement.

[0023] In the implementation process of the above scheme, the difference between the time offset and the initial time delay in at least three groups of time offset-cross-correlation calculation values ​​all meet the preset difference threshold requirement, so that the cross-correlation calculation values ​​in at least three groups of time offset-cross-correlation calculation values ​​are concentrated around the maximum value of the cross-correlation calculation with a small degree of deviation. Using these time offset-cross-correlation calculation values ​​to fit the mapping function is conducive to improving the fitting accuracy of the mapping function, and then improving the estimation accuracy of the phase error.

[0024] In a second aspect, an embodiment of the present application provides a phase error compensation method, which includes the phase error estimation method provided by the first aspect or any possible implementation of the first aspect, and using the acquired phase error to compensate for the signal to be measured to obtain a compensated signal.

[0025] In a third aspect, an embodiment of the present application provides a DAS system, including: a data acquisition card and a host computer, wherein:

[0026] The data acquisition card is used to collect the signal to be tested and send it to the host computer;

[0027] The host computer is used to obtain a reference frame and a frame to be tested of the signal to be tested; perform cross-correlation calculation on the reference frame and the frame to be tested to determine an initial time delay; wherein the initial time delay is a time offset corresponding to a maximum value of the cross-correlation calculation; use at least three groups of time offset-cross-correlation calculation values ​​for fitting to obtain a mapping function for characterizing the relationship between the time offset and the cross-correlation calculation value; obtain a correction time delay; wherein the correction time delay is a time offset corresponding to when the derivative of the mapping function is zero; use the correction time delay to correct the initial time delay to obtain a total time delay and a phase error corresponding to the total time delay.

[0028] In a fourth aspect, an embodiment of the present application provides a computer-readable storage medium, on which computer program instructions are stored. When the computer program instructions are read and executed by a processor, the method provided by the first aspect or any possible implementation of the first aspect or the method provided by the second aspect or any possible implementation of the second aspect is executed. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments of the present application will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0030] Figure 1 A flow chart of a phase error estimation method provided in an embodiment of the present application;

[0031] Figure 2 A schematic diagram of the structure of the signal collection optical path provided in the embodiment of the present application;

[0032] Figure 3 A schematic diagram of a mapping function after fitting in a certain scenario provided in an embodiment of the present application;

[0033] Figure 4 A schematic diagram of the structure of a phase error estimation device provided in an embodiment of the present application;

[0034] Figure 5 A schematic diagram of the structure of an electronic device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0035] The following will describe the technical solutions in the embodiments of the present application in conjunction with the accompanying drawings in the embodiments of the present application. The following embodiments are only used to more clearly illustrate the technical solutions of the present application, and are therefore only used as examples, and cannot be used to limit the scope of protection of the present application.

[0036] The distributed acoustic sensing (DAS) system is a fiber-optic-based sensing system that uses the fiber's sensitivity to sound (or vibration) to achieve distributed perception of acoustic signals by measuring the phase change of light in the fiber. The DAS system is widely used in resource exploration, online infrastructure safety monitoring, environmental monitoring and other fields.

[0037] When pulse jitter occurs, the pulse has a time deviation relative to the predetermined moment. In the DAS system, the time deviation caused by pulse jitter will introduce additional phase errors in each demodulation phase acquired, and eventually the demodulation phase will deviate more and more from the true phase. Related technologies usually evaluate the phase deviation and then compensate for the phase deviation. However, due to the sampling method of discrete sampling, the phase deviation estimated by the phase deviation estimation scheme in the related technology can only estimate the time delay of an integer multiple of the unit sampling time, and the estimated phase deviation has a low accuracy.

[0038] Based on this, an embodiment of the present application provides a phase error estimation method, which uses cross-correlation calculation to determine the initial delay of the signal to be measured, and then fits at least three groups of time offset-cross-correlation calculation values ​​to obtain a mapping function for characterizing the relationship between the time offset and the cross-correlation calculation value, and then obtains the correction delay, and corrects the initial delay by the correction delay, thereby obtaining the phase error. The above scheme uses the correction delay to correct the initial delay, rather than simply obtaining a delay that is an integer multiple of the unit sampling time, which is conducive to improving the phase error estimation accuracy of the above phase error estimation method. In particular, it is suitable for the calculation of phase errors less than one unit sampling time caused by pulse jitter in DAS systems.

[0039] The following is a detailed description of the above phase error estimation method. Figure 1 , an embodiment of the present application provides a phase error estimation method, the method comprising:

[0040] Step S110: obtaining a reference frame and a frame to be tested of a signal to be tested;

[0041] Step S120: performing cross-correlation calculation on the reference frame and the frame to be measured to determine an initial delay; wherein the initial delay is a time offset corresponding to a maximum value of the cross-correlation calculation;

[0042] Step S130: performing fitting using at least three groups of time offsets and cross-correlation calculation values ​​to obtain a mapping function for characterizing the relationship between the time offsets and the cross-correlation calculation values;

[0043] Step S140: Obtaining a correction delay; wherein the correction delay is a time offset corresponding to when the derivative of the mapping function is zero;

[0044] Step S150: Correct the initial delay using the correction delay to obtain the total delay and the phase error corresponding to the total delay.

[0045] First, the method of obtaining the signal to be tested in step S110 is introduced:

[0046] It can be understood that the pulse detection signal in the DAS system is generally obtained through an acquisition optical path based on the heterodyne method, and finally the signal is acquired through a data acquisition card. The acquisition scheme of the pulse detection signal of the DAS system is a relatively mature technology in this field. Please refer to the relevant technology for the specific implementation method, and the embodiments of this application will not be repeated.

[0047] In addition, the pulse detection signal is collected by the data acquisition card in frames. After a pulse is emitted into the optical fiber, the backscattered light generated by it is completely received by the detector, and the complete timing signal formed is a frame of pulse detection signal. The reference frame is a fixed frame signal for cross-correlation calculation. In practical applications, the 0th frame signal of the pulse detection signal can be set as the reference frame, and other pulse detection signals except the 0th frame signal can be set as the signal to be tested, and the i-th frame signal currently obtained in the signal to be tested is set as the frame to be tested, and the above-mentioned frame to be tested is the data selected from the signal to be tested.

[0048] The following is an introduction to the scheme of performing cross-correlation calculation on the reference frame and the frame to be measured in step S120:

[0049] The cross-correlation function is a concept in signal analysis that represents the correlation between two time series, that is, the correlation between the values ​​of signals x(t) and y(t) at any two different times t1 and t2. The cross-correlation calculation is used to measure the similarity of two signals at different time offsets. Mathematically, given signals x(t) and y(t), the cross-correlation function R xy (τ) is defined as the convolution integral of x(t) and y(t+τ) (circular convolution of the sequence in the discrete case). In digital signal processing, the cross-correlation sequence of two signals is usually calculated directly, that is, for all possible time offsets τ, the dot product of x[n] and y[n-τ] is calculated, that is:

[0050]

[0051] Among them, x[n] and y[n] are discrete sequences respectively; τ is the time offset; y[n-τ] is the y[n] sequence after time offset. In discrete sequences, n represents the index value of the midpoint of the sequence, where n = 0, 1, 2, 3...N-1; the value of τ represents the multiple of the time offset relative to the unit sampling duration. For example, τ = 3 means that the time offset is 3 times the unit sampling duration.

[0052] Since the size of the cross-correlation calculation value obtained by cross-correlation calculation is related to the similarity of the two signals, specifically: the greater the similarity between the sequence y[n-τ] after time shift and the sequence x[n], the greater the cross-correlation calculation value R xy The larger the (τ) is, the smaller the cross-correlation calculation value R is. xy The maximum value of (τ) corresponds to the maximum similarity between the x[n] sequence and the y[n-τ] sequence. At this time, the time offset τ is the initial delay.

[0053] It can be understood that, taking the example that x[n] and y[n] correspond to the reference frame and the frame to be tested respectively, since the reference frame and the frame to be tested are both discrete sequences, they each contain a number of sampling points, and the sampling time of each sampling point is separated by a sampling unit time length. Time shifting the sequence y[n] is essentially shifting a number of sampling points forward or backward. In addition, it should be pointed out that when performing cross-correlation calculations, the number of sampling points contained in the reference frame and the frame to be tested is equal. Taking the index number of the sampling points contained in the sequence x[n] as 2 to 8 as an example, the index number of the sampling points contained in the sequence y[n] when it is not time-shifted can also be 2 to 8. If y[n] is shifted forward by a unit sampling time length T s , then the sequence y[n+T s ] becomes 1 to 7. If y[n] is shifted forward by a unit sampling time length T s , then the sequence y[nT s ] becomes 3 to 9. From the above description, it can be seen that the initial delay is generally an integer multiple of the unit sampling time length.

[0054] The result of the discrete sequence cross-correlation technique can only express the delay of an integer multiple of the sampling unit time length Ts, and cannot perform more precise calculations, that is, it cannot perform delay calculations less than the unit sampling time length. The following step S130 implements precise calculations.

[0055] The following is an introduction to the scheme for obtaining the mapping function between the time offset and the cross-correlation calculation value in step S130: It can be understood that multiple sets of time offset-cross-correlation calculation values ​​will be obtained when performing cross-correlation calculation, and the multiple sets of time offset-cross-correlation calculation values ​​can be used to fit the mapping function between the time offset and the cross-correlation calculation value.

[0056] As an optional implementation of the above phase error estimation method, the differences between the time offsets and the initial time delays in at least three groups of time offset-cross-correlation calculation values ​​all meet a preset difference threshold requirement.

[0057] It can be understood that when fitting the mapping function using multiple groups of time offset-cross-correlation calculation values, multiple groups of time offset-cross-correlation calculation values ​​whose cross-correlation calculation values ​​are located near the maximum value of the cross-correlation calculation can be selected to fit the mapping function. Since the initial time delay determined in step S120 is the time offset corresponding to the maximum value of the cross-correlation calculation, the degree of deviation between the cross-correlation calculation values ​​in the selected multiple groups of time offset-cross-correlation calculation values ​​and the maximum value of the cross-correlation calculation can be controlled by controlling the size of the above-mentioned preset difference threshold. For example: the above-mentioned preset difference threshold can be set to the unit sampling time length. At this time, the cross-correlation calculation values ​​in the at least three groups of time offset-cross-correlation calculation values ​​obtained will be concentrated around the maximum value of the cross-correlation calculation with a smaller degree of deviation.

[0058] In the above scheme, the difference between the time offset and the initial time delay in at least three groups of time offset-cross-correlation calculation values ​​all meet the preset difference threshold requirement, so that the cross-correlation calculation values ​​in at least three groups of time offset-cross-correlation calculation values ​​are concentrated around the maximum value of the cross-correlation calculation with a small degree of deviation. Using these time offset-cross-correlation calculation values ​​to fit the mapping function is conducive to improving the fitting accuracy of the mapping function, and then improving the estimation accuracy of the phase error.

[0059] In addition, it can be understood that, based on experience and experiments, the mapping function of the relationship between the time offset and the cross-correlation calculation value is generally a quadratic function. Therefore, the mapping function can be determined according to the Lagrange difference theorem through at least three sets of time offset-cross-correlation calculation values.

[0060] In practical applications, the total delay of the signal to be measured may be less than the unit sampling time, for example, the pulse jitter is in the picosecond level.

[0061] At this time, the initial delay is zero. Although the correction delay can still be obtained by adopting the above steps S120 to S140, the step of determining the initial delay in step S120 will increase the amount of invalid calculation. Based on this, the embodiment of the present application provides the following solution:

[0062] As an optional implementation of the above-mentioned phase error estimation method, the above-mentioned step S120 includes: obtaining a delay estimation result of the signal to be measured; wherein the delay estimation result is used to characterize the relationship between the total delay of the signal to be measured and the unit sampling duration; if the delay estimation result is that the total delay is not less than the unit sampling duration, then performing cross-correlation calculation on the reference frame and the frame to be measured to determine the initial delay; using at least three groups of time offset-cross-correlation calculation values ​​for fitting to obtain a mapping function for characterizing the relationship between the time offset and the cross-correlation calculation value; obtaining a correction delay; using the correction delay to correct the initial delay, and obtaining the total delay and the phase error corresponding to the total delay.

[0063] It is understandable that the delay estimation result of the signal to be measured can be input by the user into the electronic device that executes the above phase error estimation method. The user can combine the hardware parameters of the DAS system (such as the hardware accuracy level) and his own experience to determine the relationship between the time offset of the DAS system and the unit sampling duration, that is, to determine whether the initial time offset is zero.

[0064] The above scheme will perform a complete cross-correlation calculation on the reference frame and the frame to be tested only when the delay estimation result shows that the total delay of the signal to be tested is not less than the unit sampling duration, that is, cross-correlation calculation is performed for all possible time offsets.

[0065] It can be understood that if the delay estimation result is that the total delay of the signal to be measured is less than the unit sampling time length, the initial time offset is zero. At this time, multiple groups of time offset-cross-correlation calculation values ​​can be directly obtained by cross-correlation calculation between the reference frame and the frame to be measured, where multiple groups refer to at least three groups. Then perform the mapping function fitting step, the correction delay acquisition step and the phase error acquisition step. The calculation amount of this scheme is not only less than the full amount of cross-correlation calculation, but also improves the execution efficiency of the above-mentioned phase error estimation method to a certain extent. At this time, the phase error estimation efficiency has met the efficiency requirements of some scenarios. Moreover, using the correction delay to correct the initial delay, obtain the total delay and the phase error corresponding to the total delay, which is conducive to suppressing the pulse jitter problem. This scheme can have a better compensation effect on picosecond level jitter, which is conducive to reducing the demodulation phase error.

[0066] As an optional implementation of the above phase error estimation method, the above step S120 includes:

[0067] Obtaining a delay estimation result of the signal to be tested; wherein the delay estimation result is used to characterize the relationship between the total delay of the signal to be tested and the unit sampling duration;

[0068] If the delay estimation result is that the total delay of the signal to be tested is less than the unit sampling time length, a reference subframe and at least three subframes to be tested are selected from the reference frame and the frame to be tested respectively; based on the reference subframe and the subframe to be tested, the mapping function used to characterize the relationship between the time offset and the cross-correlation calculation value is obtained; based on the mapping function, the correction delay is obtained; wherein, the reference subframe and the subframe to be tested contain the same number of sampling points, the reference subframe and the subframe to be tested are respectively composed of a group of continuous sampling points in the reference frame and the frame to be tested, and at least three subframes to be tested correspond to different time offsets.

[0069] It can be understood that the reference subframe and the at least three subframes to be measured are composed of some sampling points in the reference frame and the frame to be measured, which can further reduce the amount of calculation.

[0070] When the delay is less than the unit sampling time length, the above scheme helps to further reduce the calculation amount of the above phase error estimation method by fitting the mapping function and obtaining the correction delay by selecting the reference subframe and the subframe to be measured in the reference frame and the frame to be measured respectively, and thus helps to improve the execution efficiency of the above phase error estimation method.

[0071] As an optional implementation of the above-mentioned phase error estimation method, a mapping function for characterizing the relationship between the time offset and the cross-correlation calculation value is obtained based on the reference subframe and the subframe to be measured, including: performing dot product operations on the reference subframe and at least three subframes to be measured, respectively, to obtain at least three sets of time offset-cross-correlation calculation values.

[0072] It can be understood that, according to the above introduction to the principle of cross-correlation calculation, the cross-correlation calculation value can be simply understood as the dot product value of a discrete sequence and another discrete sequence. Therefore, after obtaining the reference subframe and the subframe to be measured, the cross-correlation calculation value can be directly obtained by dot product.

[0073] After obtaining the reference subframe and the subframe to be measured, the above scheme can directly obtain the cross-correlation calculation value between the reference frame and the subframe to be measured through the dot product operation between the reference subframe and the subframe to be measured, and then fit the mapping function through at least three groups of time offset-cross-correlation calculation values, which is beneficial to improving the execution efficiency of the above phase error estimation method.

[0074] It can be understood that, based on experience and experiments, when the delay estimation result is that the total delay of the signal to be measured is less than the unit sampling time length, the peak value of the cross-correlation calculation is generally near the point (0, a2), where 0 represents the initial delay of zero, and a2 represents the cross-correlation calculation value between the reference subframe and the subframe to be measured when the initial delay is zero. Therefore, when fitting the mapping function, the point (0, a2) can be considered, so that a better fitting effect can be obtained. Based on this, the embodiment of the present application provides the following solution:

[0075] As an optional implementation of the above phase error estimation method, selecting at least three subframes to be measured in the frame to be measured includes: selecting a first subframe to be measured in the frame to be measured; wherein the index of the sampling point in the first subframe to be measured is the same as the index of the sampling point in the reference subframe. For example, the index of the sampling point in the reference subframe is 2 to 8, and the index of the sampling point in the first subframe to be measured is also 2 to 8.

[0076] As an optional implementation of the above phase error estimation method, selecting at least three subframes to be tested in the frame to be tested includes: selecting a first subframe to be tested, a second subframe to be tested, and a third subframe to be tested in the frame to be tested; wherein the index of the sampling point in the first subframe to be tested is the same as the index of the sampling point in the reference subframe; the index of the sampling point in the second subframe to be tested and the index of the sampling point in the reference subframe are spaced forward by a unit sampling time length; the index of the sampling point in the third subframe to be tested and the index of the sampling point in the reference subframe are spaced backward by a unit sampling time length. This implementation is, for example:

[0077] Taking the index of the N sampling points included in the reference subframe as (a, a+N-1) as an example, the index of the N sampling points included in the first subframe to be tested is (a, a+N-1), the index of the N sampling points included in the second subframe to be tested is (a-1, a+N-2), and the index of the N sampling points included in the third subframe to be tested is (a+1, a+N).

[0078] The above scheme selects the first subframe to be measured, the second subframe to be measured and the third subframe to be measured to fit the mapping function. On the one hand, it is conducive to improving the fitting effect of the mapping function, and thus improving the accuracy of the correction delay; on the other hand, it is conducive to reducing invalid calculations and improving the estimation efficiency of the above phase error estimation method.

[0079] The following is an introduction to the scheme of correcting the initial delay by using the correction delay in step S150:

[0080] In step S150, the total delay can be obtained by directly adding the correction delay to the initial delay, and the phase error can be determined by the total delay of the signal to be measured.

[0081] Most of the phase error compensation schemes in related technologies use clock synchronization, signal filtering, and feedback algorithm control, but each has certain disadvantages or application limitations, including:

[0082] (1) Clock synchronization refers to establishing a unified time reference between various components in the system to ensure that they operate in the same timing sequence to reduce pulse jitter caused by inconsistent timing. There are many ways to achieve clock synchronization, such as using a global clock source, a distributed clock synchronization protocol, or local clock synchronization based on a phase-locked loop (PLL). By ensuring the timing consistency between various components in the system, pulse jitter caused by inconsistent timing can be effectively reduced. Clock synchronization often requires additional clock synchronization equipment (such as high-precision clock sources, clock distribution networks, synchronization protocol hardware support, etc.) and complex designs to maintain clock consistency, which increases the cost and complexity of the system.

[0083] (2) Signal filtering refers to the process of processing pulse signals through electronic filters (such as RC filters, passive filters, active filters, digital filters, etc.) to remove high-frequency noise and unnecessary frequency components, thereby reducing jitter. Filters can effectively remove high-frequency noise and unnecessary frequency components in signals, reduce jitter, and improve signal quality. Excessive filtering may cause loss of some useful information of the signal, especially for valid signals with high-frequency components, and filtering is not effective in removing jitter.

[0084] (3) Feedback control is a closed-loop control system that monitors the output signal in real time, calculates the deviation from the expected value, and adjusts the input signal accordingly to dynamically suppress pulse jitter. By monitoring the output signal and adjusting the input signal through a real-time algorithm, the system can be dynamically adjusted to suppress pulse jitter, and it has strong adaptability. However, there is currently a lack of complete feedback control algorithms and implementable correction algorithms for DAS systems. Based on this, out of the same inventive concept, the present application also provides a phase error compensation method, which includes any of the above-mentioned phase error estimation methods, and uses the acquired phase error to compensate the signal to be measured to obtain a compensated signal.

[0085] The embodiment of the present application provides a new phase error compensation method based on the phase error estimation method provided in the above embodiment. The phase error compensation method obtains the phase error according to the phase error estimation method provided in the above embodiment, and uses this to compensate the signal to be tested to obtain a compensated signal.

[0086] As an optional implementation of the above phase error compensation method, the above method of compensating the signal to be measured by using the acquired phase error to obtain the compensated signal includes:

[0087] Perform IQ demodulation on the signal to be measured to obtain a demodulated signal;

[0088] The demodulated signal is compensated using the phase error obtained by the phase error estimation method provided in the above embodiment to obtain a compensated signal.

[0089] It can be understood that the above-mentioned IQ demodulation is a relatively mature technology in this field. Please refer to the relevant technology for the specific implementation method, and the embodiments of this application will not be repeated.

[0090] In the implementation process of the above solution, a better phase compensation effect can be obtained by first performing IQ demodulation on the signal and then performing phase compensation.

[0091] The following takes the specific implementation method of the phase error compensation method in a certain scenario as an example to introduce the specific implementation principles of the above-mentioned phase error estimation method and phase error compensation method:

[0092] In the above scenario, the delay estimation result is that the total delay of the signal to be measured is less than the unit sampling time. The specific steps include:

[0093] Step 1: Collect pulse detection signals;

[0094] Conventional DAS heterodyne schemes can be used to achieve signal acquisition, see Figure 2The 1*2 coupler in the signal collection optical path divides the light emitted by the light source into local light and signal light, wherein the signal light is modulated by the acousto-optic modulator AOM and amplified by the erbium-doped fiber amplifier EDFA, and then enters the detection optical fiber through the circulator. The back Rayleigh scattered light in the detection optical fiber is reflected and output to one input port of the 2*2 coupler through the circulator. The other input port of the 2*2 coupler is used to receive local light. The output port of the 2*2 coupler is connected to a balanced detector. The output signal of the balanced detector is collected by the acquisition card. The pulse detection signal collected by the acquisition card is uploaded to the electronic device that executes the above-mentioned phase error estimation method for subsequent processing.

[0095] Step 2, respectively calculating the cross-correlation calculation values ​​a2, a1 and a3 between the reference subframe and the first subframe to be measured, the second subframe to be measured and the third subframe to be measured;

[0096] Assuming that the index numbers of the N sampling points contained in the reference subframe are (a, a+N-1), the index numbers of the N sampling points contained in the first subframe to be tested are (a, a+N-1), the index numbers of the N sampling points contained in the second subframe to be tested are (a-1, a+N-2), and the index numbers of the N sampling points contained in the third subframe to be tested are (a+1, a+N). The dot product operation is directly performed on the reference subframe and the subframe to be tested to calculate the values ​​of a2, a1, and a3 respectively:

[0097] Step 3: Use the point (-T s , a1), point (0, a2) and point (T s , a3) performing mapping function fitting;

[0098] The fitted mapping function is as follows Figure 3 As shown, Figure 3 The horizontal axis represents the time offset, and the vertical axis represents the cross-correlation calculation value. The expression of the mapping function can be:

[0099] P=a1L1+a2L2+a3L3

[0100]

[0101]

[0102]

[0103] Step 4: Calculate the correction delay;

[0104] Derivative P is obtained, and the position where the derivative is zero is the peak point of the cross-correlation calculation value, from which the correction delay can be determined. The calculation formula for the position where the derivative is zero can be:

[0105]

[0106] Substituting the values ​​of a1, a2 and a3 calculated in step 2 into the above formula can determine the correction delay Δt1. Figure 3 It can be seen that when the delay estimation result is less than the unit sampling time, the peak point of the cross-correlation calculation value is at the time offset [-T s , T s ] is within the interval. Therefore, their mutual calculation only needs to be based on the point (-T s , a1), point (0, a2) and point (T s , a3) These three points can be used to quickly solve the specific value of Δt1 through the calculation formula of Δt1, and there is no need to perform a complete mutual calculation of the entire amount.

[0107] Step 5: performing phase demodulation on the signal to be measured;

[0108] IQ demodulation mainly includes three parts: mixing, filtering and demodulation. The specific steps are as follows:

[0109] (1) Mixing: Convert the intermediate frequency signal to baseband to obtain the IQ signal;

[0110] In order to obtain the IQ signal, quadrature mixing is required, that is, two local oscillator signals with a phase difference of 90 degrees are multiplied with the input signal to generate two components, I (In-phase) and Q (Quadrature).

[0111] (2) Filtering: Remove unwanted frequency components, especially image frequencies and other spurious signals generated during the mixing process, and retain the required signal bandwidth;

[0112] In this step, a low-pass filter can be used to remove the image frequency component generated by mixing, and only the baseband signal after the carrier is removed is retained;

[0113] (3) Demodulation: Use the I and Q signals as the basis for complex signal processing to restore the complex signal, s(t) = I(t) + jQ(t), where j represents the imaginary unit.

[0114] Step 6: Perform phase compensation;

[0115] After the DAS system is heterodyned by AOM, the intermediate frequency of the signal is f IF , after being affected by the correction delay Δt1, the additional phase error (or phase deviation) introduced is 2πfΔt1, so the complex signal of the compensated phase can be expressed as:

[0116] s′(t)=s(t)exp(-2πf IF Δt1)

[0117] This results in a phase-compensated signal.

[0118] The above implementation method determines the phase compensation by estimating the correction delay, which is beneficial to suppressing the pulse jitter problem. This solution can have a good compensation effect on the jitter at the picosecond level and is beneficial to reducing the demodulation phase error.

[0119] Based on the same inventive concept, a DAS system is also provided in an embodiment of the present application, the system includes a data acquisition card and a host computer, wherein:

[0120] The data acquisition card is used to collect the signal to be tested and send it to the host computer;

[0121] The host computer is used to execute any one of the above-mentioned phase error estimation methods or phase error compensation methods.

[0122] See also Figure 4 Based on the same inventive concept, the embodiment of the present application further provides a phase error estimation device 200, which includes:

[0123] The frame acquisition module 210 is used to acquire the reference frame and the frame to be tested of the signal to be tested;

[0124] The initial delay determination module 220 is used to perform cross-correlation calculation on the reference frame and the frame to be measured to determine the initial delay; wherein the initial delay is the time offset corresponding to the maximum value of the cross-correlation calculation;

[0125] A mapping function acquisition module 230, configured to perform fitting using at least three sets of time offset-cross-correlation calculation values ​​to acquire a mapping function for characterizing the relationship between the time offset and the cross-correlation calculation value;

[0126] A correction delay acquisition module 240 is used to acquire a correction delay; wherein the correction delay is a time offset corresponding to when the derivative of the mapping function is zero;

[0127] The phase error acquisition module 250 uses the correction delay to correct the initial delay, and obtains the total delay and the phase error corresponding to the total delay.

[0128] As an optional implementation manner of the above-mentioned phase error estimation device, the above-mentioned initial delay determination module 220 is specifically used to: obtain the delay estimation result of the signal to be measured; wherein the delay estimation result is used to characterize the size relationship between the total delay of the signal to be measured and the unit sampling duration; if the delay estimation result is that the total delay is not less than the unit sampling duration, then the reference frame and the frame to be measured are cross-correlated to determine the initial delay; at least three groups of the time offset-cross-correlation calculation values ​​are used for fitting to obtain the mapping function used to characterize the relationship between the time offset and the cross-correlation calculation value; obtain the correction delay; and use the correction delay to correct the initial delay to obtain the phase error.

[0129] As an optional implementation manner of the above-mentioned phase error estimation device, the above-mentioned initial delay determination module 220 is specifically used to: obtain the delay estimation result of the signal to be tested; wherein the delay estimation result is used to characterize the size relationship between the total delay of the signal to be tested and the unit sampling duration; if the delay estimation result is that the total delay is less than the unit sampling duration, then select a reference subframe and at least three subframes to be tested in the reference frame and the frame to be tested respectively; based on the reference subframe and the subframe to be tested, obtain the mapping function used to characterize the relationship between the time offset and the cross-correlation calculation value; based on the mapping function, obtain the correction delay; wherein the reference subframe and the subframe to be tested contain the same number of sampling points, the reference subframe and the subframe to be tested are respectively composed of a group of continuous sampling points in the reference frame and the frame to be tested, and at least three subframes to be tested correspond to different time offsets.

[0130] As an optional implementation manner of the above-mentioned phase error estimation device, the above-mentioned initial delay determination module 220 obtains the mapping function for characterizing the relationship between the time offset and the cross-correlation calculation value based on the reference subframe and the subframe to be measured, including:

[0131] Perform dot product operations on the reference subframe and at least three subframes to be measured respectively to obtain at least three groups of time offset-cross-correlation calculation values.

[0132] As an optional implementation manner of the above-mentioned phase error estimation device, the above-mentioned initial delay determination module 220 selects at least three subframes to be measured in the frame to be measured, including: selecting a first subframe to be measured in the frame to be measured; wherein the index of the sampling point in the first subframe to be measured is the same as the index of the sampling point in the reference subframe.

[0133] As an optional implementation manner of the above-mentioned phase error estimation device, the above-mentioned initial delay determination module 220 selects at least three subframes to be measured in the frame to be measured, including: selecting a first subframe to be measured, a second subframe to be measured and a third subframe to be measured in the frame to be measured; wherein the index of the sampling point in the first subframe to be measured is the same as the index of the sampling point in the reference subframe; the index of the sampling point in the second subframe to be measured and the index of the sampling point in the reference subframe are spaced forward by one unit sampling time length; the index of the sampling point in the third subframe to be measured and the index of the sampling point in the reference subframe are spaced backward by one unit sampling time length.

[0134] Based on the same concept, an embodiment of the present application further provides a phase error compensation device, which includes: the above-mentioned phase error estimation device 200 and a phase compensation module, wherein:

[0135] The phase compensation module is used to compensate the demodulated signal using the acquired phase error to obtain a compensated signal.

[0136] As an optional implementation manner of the above-mentioned phase error estimation device, the difference between the time offset and the initial time delay in at least three groups of the time offset-cross-correlation calculation values ​​all meet a preset difference threshold requirement.

[0137] Figure 5 A schematic diagram of an electronic device provided in an embodiment of the present application. Figure 5 The electronic device 300 includes: a processor 310, a memory 320 and a communication interface 330. These components are interconnected and communicate with each other through a communication bus 340 and / or other forms of connection mechanisms (not shown).

[0138] The memory 320 includes one or more (only one is shown in the figure), which may be, but not limited to, a random access memory (RAM), a read only memory (ROM), a programmable read-only memory (PROM), an erasable programmable read-only memory (EPROM), an electrically erasable programmable read-only memory (EEPROM), etc. The processor 310 and other possible components may access the memory 320 and read and / or write data therein.

[0139] The processor 310 includes one or more (only one is shown in the figure), which can be an integrated circuit chip with signal processing capabilities. The above-mentioned processor 310 can be a general-purpose processor, including a central processing unit (CPU), a micro controller unit (MCU), a network processor (NP) or other conventional processors; it can also be a special-purpose processor, including a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic devices, discrete gates or transistor logic devices, discrete hardware components.

[0140] The communication interface 330 includes one or more (only one is shown in the figure), which can be used to communicate directly or indirectly with other devices to exchange data. For example, the communication interface 330 can be an Ethernet interface; it can be a mobile communication network interface, such as an interface of a 3G, 4G, or 5G network; or it can be other types of interfaces with data transceiving functions.

[0141] One or more computer program instructions may be stored in the memory 320 , and the processor 310 may read and execute these computer program instructions to implement the phase error estimation method or phase error compensation method provided in the embodiments of the present application and other desired functions.

[0142] Understandably, Figure 5 The structure shown is for illustration only. The electronic device 300 may also include Figure 5 More or fewer components as shown, or with Figure 5 Different configurations are shown. Figure 5 Each component shown in the figure can be implemented by hardware, software or a combination thereof. For example, the electronic device 300 can be a single server (or other device with computing processing capabilities), a combination of multiple servers, a cluster of a large number of servers, etc., and can be both a physical device and a virtual device.

[0143] The present application also provides a computer-readable storage medium, which stores computer program instructions. When the computer program instructions are read and executed by a computer processor, the phase error estimation method or phase error compensation method provided by the present application is executed. For example, the computer-readable storage medium can be implemented as Figure 5 The memory 320 in the electronic device 300.

[0144] In the embodiments provided in the present application, it should be understood that the disclosed devices and methods can be implemented in other ways. The device embodiments described above are merely schematic. For example, the division of the units is only a logical function division. There may be other division methods in actual implementation. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some communication interfaces, and the indirect coupling or communication connection of the devices or units can be electrical, mechanical or other forms.

[0145] In addition, the units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0146] Furthermore, the functional modules in the various embodiments of the present application may be integrated together to form an independent part, or each module may exist separately, or two or more modules may be integrated to form an independent part.

[0147] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" in the specification and claims of this application and the above-mentioned figure descriptions and any variations thereof are intended to cover non-exclusive inclusions.

[0148] In the description of the embodiments of the present application, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meaning of "multiple" is more than two, unless otherwise clearly and specifically defined.

[0149] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0150] In the description of the embodiments of the present application, the term "and / or" is only a description of the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0151] The above description is only an embodiment of the present application and is not intended to limit the protection scope of the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A phase error estimation method, characterized in that: The method comprises: Acquire a reference frame and a frame to be measured of a signal to be measured; Performing cross-correlation calculation on the reference frame and the frame to be measured to determine an initial time delay; wherein the initial time delay is a time offset corresponding to a maximum value of the cross-correlation calculation; Using at least three groups of time offset-cross-correlation calculation values ​​for fitting, a mapping function for characterizing the relationship between the time offset and the cross-correlation calculation value is obtained; Obtaining a correction delay; wherein the correction delay is a time offset corresponding to when the derivative of the mapping function is zero; The initial time delay is corrected using the correction time delay to obtain a total time delay and a phase error corresponding to the total time delay.

2. The phase error estimation method according to claim 1, characterized in that: The step of performing cross-correlation calculation on the reference frame and the frame to be measured to obtain an initial delay includes: Obtaining a delay estimation result of the signal to be tested; wherein the delay estimation result is used to characterize the relationship between the total delay of the signal to be tested and the unit sampling duration; If the delay estimation result is that the total delay is not less than the unit sampling time length, the reference frame and the frame to be measured are cross-correlated to determine the initial delay; at least three groups of the time offset-cross-correlation calculation values ​​are used for fitting to obtain the mapping function used to characterize the relationship between the time offset and the cross-correlation calculation value; the correction delay is obtained; and the initial delay is corrected using the correction delay to obtain the phase error.

3. The phase error estimation method according to claim 1, characterized in that: The step of performing cross-correlation calculation on the reference frame and the frame to be measured to obtain an initial delay includes: Obtaining a delay estimation result of the signal to be tested; wherein the delay estimation result is used to characterize the relationship between the total delay of the signal to be tested and the unit sampling duration; If the delay estimation result is that the total delay is less than the unit sampling duration, a reference subframe and at least three subframes to be tested are selected from the reference frame and the frame to be tested respectively; based on the reference subframe and the subframe to be tested, the mapping function used to characterize the relationship between the time offset and the cross-correlation calculation value is obtained; based on the mapping function, the correction delay is obtained; wherein the reference subframe and the subframe to be tested contain the same number of sampling points, the reference subframe and the subframe to be tested are respectively composed of a group of continuous sampling points in the reference frame and the frame to be tested, and at least three subframes to be tested correspond to different time offsets.

4. The phase error estimation method according to claim 3, characterized in that: The acquiring, based on the reference subframe and the subframe to be measured, the mapping function used to characterize the relationship between the time offset and the cross-correlation calculation value comprises: Perform dot product operations on the reference subframe and at least three subframes to be measured respectively to obtain at least three groups of time offset-cross-correlation calculation values.

5. The phase error estimation method according to claim 3, characterized in that: Selecting at least three subframes to be tested from the frame to be tested includes: A first subframe to be tested is selected from the frame to be tested; wherein the index of the sampling points in the first subframe to be tested is the same as the index of the sampling points in the reference subframe.

6. The phase error estimation method according to claim 3, characterized in that: Selecting at least three subframes to be tested from the frame to be tested includes: A first subframe to be tested, a second subframe to be tested and a third subframe to be tested are selected from the frame to be tested; wherein the index of the sampling point in the first subframe to be tested is the same as the index of the sampling point in the reference subframe; the index of the sampling point in the second subframe to be tested and the index of the sampling point in the reference subframe are spaced forward by one unit sampling time length; the index of the sampling point in the third subframe to be tested and the index of the sampling point in the reference subframe are spaced backward by one unit sampling time length.

7. The phase error estimation method according to claim 1, characterized in that: The differences between the time offsets and the initial time delays in at least three groups of the time offset-cross-correlation calculation values ​​all meet a preset difference threshold requirement.

8. A phase error compensation method, characterized in that: The method comprises the phase error estimation method according to any one of claims 1 to 7, and The obtained phase error is used to compensate the signal to be measured to obtain a compensated signal.

9. A DAS system, characterized in that: The distributed acoustic sensing DAS system includes: a data acquisition card and a host computer, wherein: The data acquisition card is used to collect the signal to be tested and send it to the host computer; The host computer is used to execute the method according to any one of claims 1 to 8.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores computer instructions, and when the computer instructions are executed by a computer, the computer is caused to perform the method according to any one of claims 1 to 8.

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