A high-precision trigger correction method for a digital oscilloscope based on adaptive learning

Abstract

The application discloses a high-precision trigger correction method for a digital oscilloscope based on adaptive learning, and the method comprises the following steps: inputting an output signal of an arbitrary waveform generator into the digital oscilloscope to complete waveform data acquisition and buffering; then, setting a horizontal time base position of the digital oscilloscope, and enabling a trigger correction function of the digital oscilloscope; and through adaptive high-precision trigger correction, unstable trigger waveforms are corrected into stable trigger waveforms, so that the trigger precision of the collected trigger waveforms is greatly improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of digital oscilloscope, more specifically, to a high-precision trigger correction method for digital oscilloscope based on adaptive learning. BACKGROUND

[0002] With the development and continuous application of electronic measurement field, the demand for distributed acquisition application and transient test is increasingly strict, and high-precision trigger has become a key indicator of electronic measuring instruments. In order to capture the waveform of interest and expectation of users and make the waveform stable display, the trigger function has become an indispensable part of time domain test instruments represented by digital oscilloscope. As a significant feature of digital storage oscilloscope (DSO), with the continuous improvement of sampling rate of digital storage oscilloscope, the demand for high-precision trigger is increasingly urgent. In the traditional digital oscilloscope, the waveform trigger is to use the hardware comparison signal to directly map to the data, and to obtain the stable trigger waveform accordingly. This processing can be used in the oscilloscope with low sampling rate and low trigger precision requirement, but in the application of high-performance oscilloscope, the direct mapping of trigger signal brings great trigger error and trigger jitter problem, as shown in Figure 1 There are three cases of trigger waveform, which are respectively leading trigger waveform, ideal trigger waveform and lagging trigger waveform.

[0003] On the high sampling rate oscilloscope, due to the difficulty of FPGA internal working clock to reach GHz or above, and the sampling rate of ADC is usually in GSPS, therefore, the common method is to convert serial data into parallel data to ensure the data quantity unchanged, at this time, the trigger signal will be mapped to the parallel road number at the same time, it is difficult to ensure the correct trigger at a certain sampling point, and the trigger jitter is related to the parallel road number of data.

[0004] The disadvantages of the traditional trigger method mainly include the following aspects:

[0005] (1) The hardware circuit design is strict and meticulous, the signal noise and trigger edge distortion will bring the mis-triggering effect, resulting in the trigger waveform being a non-interested waveform;

[0006] (2) The parallel processing in FPGA is difficult to determine the trigger point, when the oscilloscope processes the interpolation measurement gear, the trigger point jitter error will be larger, and the trigger waveform jitter is obvious;

[0007] (3) The external trigger edge signal and the FPGA internal processing clock are asynchronous, and there are differences in the setup time and hold time of different semiconductor devices, so the trigger position is not correct when analyzing;

[0008] (4), the minimum trigger precision is related to the ADC sampling rate, and in the real-time sampling gear, the trigger precision is the minimum sampling interval, so it is difficult to realize higher hardware trigger precision.

[0009] In summary, most of the current conventional trigger methods cannot meet the requirements of high sampling rate and high trigger precision, especially in the multi-channel oscilloscope trigger application, the accuracy of the trigger position, trigger jitter and other problems cannot be guaranteed. SUMMARY

[0010] The present application aims to overcome the shortcomings of the prior art, and provides a digital oscilloscope high-precision trigger correction method based on adaptive learning, to improve the accuracy of the trigger position and reduce the trigger jitter.

[0011] To achieve the above-mentioned application purposes, the present application is a digital oscilloscope high-precision trigger correction method based on adaptive learning, characterized in that it comprises the following steps:

[0012] (1), waveform data acquisition and caching;

[0013] The output signal of the arbitrary waveform generator is input to the digital oscilloscope, and the stable parallel acquisition waveform is obtained by the acquisition system in the digital oscilloscope, and the analog trigger signal is obtained by the comparator in the digital oscilloscope;

[0014] When the FPGA in the digital oscilloscope detects the rising edge of the analog trigger signal, the FPGA controls the parallel acquisition waveform data to be cached to the parallel FIFO, until the parallel FIFO is full;

[0015] (2), set the horizontal time base gear of the digital oscilloscope, and enable the trigger correction of the digital oscilloscope;

[0016] (2.1), read the parallel data from the parallel FIFO, and then perform parallel-to-serial conversion to obtain serial input data;

[0017] (2.2), construct a two-dimensional waveform array through the serial input data;

[0018] (2.3), determine whether each row of waveform data in the two-dimensional waveform array is a single-period waveform, if not, go to step (2.4); otherwise, keep the two-dimensional waveform array unchanged, denoted as:

[0019]

[0020] (2.4), extract the single-period waveform data of each row of waveform data in the two-dimensional waveform array X, and then construct a new two-dimensional waveform array

[0021] (2.5), construct an attribute matrix A;

[0022] (2.6), obtaining the actual trigger point;

[0023] In the attribute matrix A, the average value x of the first column is imean The mode x is obtained by the mode method, and then the position index value p in the corresponding row is mapped according to the mode x iindex , and the position where p iindex is located is the actual trigger point and is used as the reference position index value for subsequent correction;

[0024] (2.7), the acquisition system in the digital oscilloscope obtains the position index value of the next trigger waveform when the next sampling period comes, according to steps (2.1)-(2.6) Then, according to the reference position index value p iindex , the trigger waveform is corrected, and after the correction is completed, the waveform is displayed;

[0025] Then, by analogy, in the subsequent sampling period, the adaptive learning correction process after waveform triggering is completed.

[0026] The invention purpose of the present application is realized as follows:

[0027] The high-precision trigger correction method of the digital oscilloscope based on adaptive learning of the present application inputs the output signal of the arbitrary waveform generator into the digital oscilloscope, completes waveform data acquisition and caching, then sets the horizontal time base position of the digital oscilloscope, opens the trigger correction enable of the digital oscilloscope, and corrects the unstable trigger waveform into a stable trigger waveform through adaptive high-precision trigger correction, greatly improving the trigger precision of the collected trigger waveform.

[0028] Meanwhile, the high-precision trigger correction method of the digital oscilloscope based on adaptive learning of the present application has the following beneficial effects:

[0029] (1), an advanced adaptive learning mechanism is adopted, combined with trigger correction technology, the digital oscilloscope can significantly improve the trigger precision, and its actual performance not only exceeds the traditional limit, but also breaks through the physical limit of ADC sampling precision, realizing more accurate signal capture capability.

[0030] (2), the high-precision trigger correction strategy for sampling data can significantly reduce the design threshold and challenge of the hardware trigger circuit, simplify the hardware circuit composition, effectively save the precious circuit layout area, and promote the miniaturization and cost optimization of the equipment;

[0031] (3), by implementing correction processing algorithm to the original sampling signal, the complexity of the trigger logic design inside the FPGA is simplified, not only effectively avoiding the logical processing problem caused by the cross clock domain between the external trigger signal and the sampling data, but also significantly optimizing the logic circuit architecture inside the FPGA, improving the performance and stability of the overall system. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 is a waveform diagram of early trigger, ideal trigger and late trigger;

[0033] Figure 2 is the relationship between the analog trigger position and the sampling point of the high sampling rate digital oscilloscope;

[0034] Figure 3 is the flow chart of the high-precision trigger correction method of the digital oscilloscope based on adaptive learning of the present application;

[0035] Figure 4 is an uncorrected analog waveform diagram;

[0036] Figure 5 is an analog waveform diagram after adaptive learning trigger correction. DETAILED DESCRIPTION

[0037] The specific embodiments of the present application will be described below in conjunction with the accompanying drawings, so that those skilled in the art can better understand the present application. It should be particularly noted that in the following description, when the detailed description of known functions and designs may obscure the main content of the present application, these descriptions will be omitted here.

[0038] EMBODIMENT

[0039] In this embodiment, in order to better illustrate the technical solutions of the present scheme, first, the waveform of the digital oscilloscope from acquisition, trigger to display process is simply introduced. The digital oscilloscope system is composed of conditioning channel, acquisition module, signal processing module, main control and display module. Among them, the digital oscilloscope acquisition framework is composed of analog-to-digital converter (ADC) and field programmable device (FPGA). Triggering as a significant feature of digital oscilloscope, high-precision trigger is particularly important for fine acquisition.

[0040] As shown in Figure 2 , under the data clock, the relationship between the trigger point and the sampling point data is: one trigger time corresponds to 8 sampling points. Since the trigger point and the sampling point in the sampling system are not one-to-one correspondence, the trigger jitter problem occurs, but its jitter range will only exist in X(8)~X(16), so the actual trigger point is also in it.

[0041] The application solves the limitation of needing additional hardware circuit to measure the trigger time and the sampling clock interval, and directly analyzes the data after the trigger to obtain the trigger time, so that high-precision trigger function can be realized as long as basic trigger structure and sampling data.

[0042] The application will be described in detail below, as shown in the following figure, and the specific steps are as follows: Figure 3

[0043] (1), waveform data acquisition and caching;

[0044] In this embodiment, an arbitrary waveform generator or a radio frequency signal source is connected to the digital oscilloscope, the arbitrary waveform generator or the radio frequency signal source generates an output signal satisfying the sampling law (the sampling frequency is more than twice the frequency of the sampled signal), the output signal is input to the digital oscilloscope, the stable parallel acquisition waveform is obtained by the acquisition system in the digital oscilloscope, and the analog trigger signal is obtained by the comparator in the digital oscilloscope.

[0045] According to the acquisition trigger principle of the digital oscilloscope, when the FPGA in the digital oscilloscope detects the rising edge of the analog trigger signal, the FPGA controls the parallel acquisition waveform data to be cached in 8 parallel FIFOs, the depth of each FIFO is 16k, and the parallel FIFO is written until it is full.

[0046] (2), set the horizontal time base position of the digital oscilloscope, and enable the trigger correction of the digital oscilloscope;

[0047] The digital oscilloscope generally has interpolation, real-time and extraction horizontal time base positions, and the waveform has been collected stably under the condition of low sampling rate in the large extraction position, and the waveform display is also stable, so the trigger correction is not needed.

[0048] In this embodiment, the application provides an enabling interface, which can automatically judge and perform the enabling operation according to the horizontal time base position set by the user, that is, the trigger correction function can be enabled, and the specific correction process is as follows:

[0049] (2.1), read the parallel data from the parallel FIFO, and then perform parallel-serial conversion to obtain serial input data;

[0050] (2.2), construct a two-dimensional waveform array through the serial input data;

[0051] Supposing that the serial input data contains 1000 waveforms, and each waveform contains 1024 sampling points, each row of the two-dimensional waveform array represents a waveform, and the elements in each row are the sampling points of each waveform, so that the two-dimensional waveform array with the size of MxN=1000x1024 is obtained. ​

[0052] (2.3), judge whether each row waveform data in the two-dimensional waveform array is a single period waveform, if not, go to step (2.4); otherwise, keep the two-dimensional waveform array unchanged, denoted as:

[0053]

[0054] (2.4), extract the single period waveform data of each row waveform data in the two-dimensional waveform array X, and then build a new two-dimensional waveform array

[0055] Take the data in the first row as the reference, find the edge of the waveform, extract the waveform data in the first row of the two-dimensional waveform array X, and then find the starting point and the ending point of any one period in the waveform data in the first row, and then extract the elements between the starting point and the ending point, denoted as n is the number of elements between the starting point and the ending point;

[0056] Take the element Take the n elements in the corresponding position in the remaining M-1 rows of waveform data in the two-dimensional waveform array X as the reference, and build a new two-dimensional waveform array

[0057]

[0058] (2.5), build the attribute matrix A;

[0059] For convenience of description, denote the two-dimensional waveform array X and The number of elements in each row of the two-dimensional waveform array is k, and then calculate the average value x imean of each row of elements in the two-dimensional waveform array, i=1, 2, …, M;

[0060]

[0061] Wherein, x ij represents the element corresponding to the i-th row and the j-th column in the two-dimensional waveform array, j=1, 2, …, k;

[0062] Find the position index value p iindex

[0063]

[0064] Build the attribute matrix A with the average value x imean of each row and the position index value p iindex

[0065]

[0066] ​(2.6), obtaining the actual trigger point;

[0067] In the attribute matrix A, the average value x of the first column is imean The mode x is obtained by the mode method, and then the position index value p in the corresponding row is mapped according to the mode x iindex , and the position where p iindex is located is the actual trigger point and is used as the reference position index value for subsequent correction;

[0068] (2.7), the acquisition system in the digital oscilloscope obtains the position index value of the next trigger waveform when the next sampling period comes according to steps (2.1)-(2.6) Then, the trigger waveform is corrected according to the reference position index value p iindex When , the trigger waveform needs to be moved forward by When , the trigger waveform needs to be moved backward by

[0069] After the correction is completed, the waveform is displayed, and then the adaptive learning correction process after waveform triggering is completed in the subsequent sampling period.

[0070] Experimental demonstration

[0071] According to the above principle, set the arbitrary waveform generator to output a 1kHz square wave signal, connect the output signal to the input channel of the digital oscilloscope, first enable the high-precision trigger correction function of the invention, set the digital oscilloscope to the appropriate time base position, select the rising edge trigger of the oscilloscope trigger mode, adjust the digital oscilloscope interface to display only one rising edge waveform, turn on the digital oscilloscope afterglow mode, and observe the waveform display, as shown in Figure 4 Then enable the high-precision trigger correction function of the invention, set the digital oscilloscope to the appropriate time base position, select the rising edge trigger of the oscilloscope trigger mode, adjust the digital oscilloscope interface to display only one rising edge waveform, turn on the digital oscilloscope afterglow mode, and observe the waveform display, as shown in Figure 5 Through the comparison and analysis of Figure 4 and Figure 5 , the analog waveform after adaptive learning trigger correction of the invention can greatly improve the trigger precision of the digital oscilloscope.

[0072] Although the above describes the specific embodiments of the invention for the purpose of facilitating the understanding of the invention by those skilled in the art, it should be clear that the invention is not limited to the scope of the specific embodiments, and for those skilled in the art, it is obvious that various changes are within the spirit and scope of the invention defined and determined by the appended claims, and all inventions utilizing the concept of the invention are within the scope of protection.

Claims

1. A high-precision trigger calibration method for digital oscilloscopes based on adaptive learning, characterized in that, Includes the following steps: (1) Waveform data acquisition and buffering; The output signal of the arbitrary waveform generator is input to the digital oscilloscope, and a stable parallel acquisition waveform is obtained by sampling through the acquisition system inside the digital oscilloscope. The analog trigger signal is obtained by shaping through the comparator inside the digital oscilloscope. When the FPGA in the digital oscilloscope detects the rising edge of the analog trigger signal, the FPGA controls the parallel acquisition of waveform data and buffers it into the parallel FIFO until the parallel FIFO is full. (2) Set the horizontal time base of the digital oscilloscope and enable the trigger calibration of the digital oscilloscope; (2.1) Read parallel data from the parallel FIFO, and then perform parallel-to-serial conversion to obtain serial input data; (2.2) Construct a two-dimensional waveform array by serially inputting data; (2.3) Determine whether each row of waveform data in the two-dimensional waveform array is a single-cycle waveform. If not, proceed to step (2.4); otherwise, keep the two-dimensional waveform array unchanged and denote it as: ； (2.4) Extracting the two-dimensional waveform array The single-cycle waveform data of each row of waveform data is then used to construct a new two-dimensional waveform array. ; (2.5) Constructing the attribute matrix ; Two-dimensional waveform array and The number of elements in each row of the array is Then calculate the average value of each row of elements in the two-dimensional waveform array. , ; Find the index of the element in each row that is closest to the average value. ; Average of each row and location index value Constructing the attribute matrix ; ； (2.6) Obtain the actual trigger point; In the attribute matrix In the middle, the average value of the first column Find the mode using the mode method. Then based on the mode Map the position index value in the corresponding row ,remember The location is the actual trigger point and serves as the reference position index value for subsequent corrections; (2.7) When the next sampling period arrives, the acquisition system in the digital oscilloscope calculates the position index value of the next trigger waveform according to steps (2.1) to (2.6). Then, based on the reference position index value The trigger waveform is calibrated, and the waveform is displayed after calibration is completed. Then, by analogy, the adaptive learning and correction process after waveform triggering is completed in subsequent sampling periods.

2. The high-precision triggering and calibration method for digital oscilloscopes based on adaptive learning according to claim 1, characterized in that, The construction process of the two-dimensional waveform array is as follows: Suppose the serial input data contains M waveforms, each waveform containing N sampling points. Then, each row of the two-dimensional waveform array represents one waveform, and the elements in each row are the number of sampling points for each waveform, thus obtaining a data array of size M. A two-dimensional waveform array.

3. The high-precision triggering and calibration method for digital oscilloscopes based on adaptive learning according to claim 1, characterized in that, In step (2.4), a new two-dimensional waveform array is constructed. The method is as follows: Extracting two-dimensional waveform arrays Take the first row of waveform data, then find the start and end points of any cycle in the first row of waveform data, and then extract the elements between the start and end points, denoted as . , The number of elements between the starting point and the ending point; With elements In a two-dimensional waveform array Using the position of the first row as a reference, in the two-dimensional waveform array the remaining Take the corresponding position from the line waveform data Each element point is used to construct a new two-dimensional waveform array. : 。 4. The high-precision triggering and calibration method for digital oscilloscopes based on adaptive learning according to claim 1, characterized in that, The method for constructing the attribute matrix in step (2.5) is as follows: For ease of description, let's call it a two-dimensional waveform array. and The number of elements in each row of the array is Then calculate the average value of each row of elements in the two-dimensional waveform array. , ; ； in, Represents the second wave in a two-dimensional waveform array. Line number The elements corresponding to the column, ; Find the index of the element in each row that is closest to the average value. ; ； Average of each row and location index value Constructing the attribute matrix ; 。 5. The high-precision triggering and calibration method for digital oscilloscopes based on adaptive learning according to claim 1, characterized in that, In step (2.7), the reference position index value is used. The method for correcting the trigger waveform is as follows: when At this time, the trigger waveform needs to be moved forward. ;when At this time, the trigger waveform needs to be shifted backward. .

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