Digital oscilloscope frequency domain triggering method based on direct digital integration method

Abstract

The application discloses a digital oscilloscope frequency domain trigger method based on a direct digital integration method, a group of cosine waves of specific frequencies are generated through self-defined analysis frequency bands and frequency resolutions, then a measured signal is multiplied by the cosine waves of the specific frequencies and integrated, energy of the signal on the frequency component is directly obtained, and finally the analysis result is used for a frequency domain trigger function in the oscilloscope.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of digital oscilloscope, more specifically, it relates to a digital oscilloscope frequency domain trigger method based on direct digital integration method. BACKGROUND

[0002] Trigger function is an essential part of oscilloscope design, the current common trigger method is designed for the time domain characteristics of the measured signal, which may not capture the signal concerned by the user in a more complex scenario.

[0003] Trigger function is also the key to the target signal captured by the oscilloscope, the common trigger method such as edge trigger, level trigger, etc. is from the time domain characteristics of the measured signal, by comparing the characteristics of the measured signal with the size of the preset value to control the read and write enable of the storage module, thereby realizing the trigger function.

[0004] But with the complication of signal in engineering application, the single time domain trigger method has been unable to meet the user's demand for capturing target signal, so it is necessary to start from other information domain, and research the frequency domain trigger module independent of the time domain trigger module.

[0005] Spectrum analysis is a key technology in signal processing, which is used to reveal the energy distribution of signals at different frequency components. It has wide application in communication, radar, speech processing, medical signal analysis and other fields. Generally, spectrum analysis converts time domain signal into frequency domain signal through Fourier transform, so as to show the strength of the signal at each frequency component.

[0006] FFT is an algorithm for efficient calculation of Fourier transform, which makes spectrum analysis feasible and efficient by reducing the computational complexity. FFT can quickly calculate the amplitude and phase information of the signal in the full spectrum, providing detailed frequency distribution, which is the standard method of spectrum analysis. FFT is particularly suitable for obtaining complete spectrum diagram, and is widely used in wideband signal analysis. However, the frequency resolution of FFT depends on the sampling rate and signal length, and the frequency distribution is fixed with equal interval. Although it is suitable for full-band analysis, the flexibility of FFT is particularly insufficient in application scenarios that require custom frequency resolution or only focus on certain specific frequency bands. SUMMARY

[0007] The purpose of the present application is to overcome the shortcomings of the prior art, and to provide a digital oscilloscope frequency domain trigger method based on direct digital integration method, which directly obtains the energy component of the signal at a certain frequency by multiplying and integrating the measured signal with the cosine signal of the frequency, and then uses it in the trigger function of the digital oscilloscope.

[0008] To achieve the above-mentioned purposes of the application, the frequency domain triggering method of a digital oscilloscope based on a direct digital integration method comprises the following steps:

[0009] (1) setting the analysis bandwidth and frequency resolution of the frequency domain triggering module on the software end of the digital oscilloscope;

[0010] (2) generating a plurality of cosine waves corresponding to the frequencies according to the analysis bandwidth and resolution on the software end;

[0011] (3) performing discrete processing on each cosine wave to generate cosine wave coefficients of the respective frequencies;

[0012] (4) downloading the cosine wave coefficients to the coefficient access module on the hardware end and storing them in a matrix form on the software end;

[0013] (5) reading the sampling data and the cosine wave coefficients by the calculation module to perform direct digital integration;

[0014] (6) generating a triggering signal according to the comparison result of the direct digital integration result and a preset triggering value by the triggering module;

[0015] The purposes of the application are achieved as follows:

[0016] The frequency domain triggering method of the digital oscilloscope based on the direct digital integration method generates a group of cosine waves of specific frequencies by defining the analysis frequency band and the frequency resolution, then multiplies the measured signal with the cosine waves of the specific frequencies and integrates them to directly obtain the energy of the signal at the frequency component, and finally uses the analysis result for the frequency domain triggering function in the oscilloscope.

[0017] Meanwhile, the frequency domain triggering method of the digital oscilloscope based on the direct digital integration method has the following advantages:

[0018] Beneficial effects:

[0019] (1) The application defines the analysis bandwidth and resolution, then acquires the frequency spectrum characteristics of the measured signal by performing digital integration on the measured signal and the cosine signal of the corresponding frequency, realizes more targeted narrowband analysis, greatly improves the flexibility of the spectrum analysis, and reduces the resource consumption.

[0020] (2) The application realizes the self-defined triggering mechanism for special signals by combining the spectrum analysis based on the direct digital integration with the frequency domain template triggering, greatly improves the accuracy of the frequency domain triggering module, and enriches the selection of the triggering mode. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 is the principle diagram of the frequency domain triggering method of the digital oscilloscope based on the direct digital integration method of the application;

[0022] Figure 2 is a storage matrix diagram;

[0023] Figure 3 is an operation diagram of a parallel summation unit;

[0024] Figure 4 is a comparator processing diagram in a trigger module. DETAILED DESCRIPTION

[0025] The specific embodiments of the present application are described below with reference to the accompanying drawings in order to better understand the present application by those skilled in the art. It should be particularly noted that in the following description, when detailed description of known functions and designs may obscure the main content of the present application, these descriptions will be omitted here.

[0026] EMBODIMENT

[0027] In this embodiment, as shown in the figure, a frequency domain trigger method of a digital oscilloscope based on a direct digital integration method comprises the following steps: Figure 1

[0028] (1) Set the analysis bandwidth and the frequency resolution of the frequency domain trigger module at the software end of the digital oscilloscope;

[0029] Set the analysis bandwidth B of the frequency domain trigger module, and the analysis bandwidth B can completely cover the measured signal;

[0030] Set the frequency resolution f0 of the frequency domain trigger module, and the frequency resolution f0 is less than the minimum value of the difference between any two adjacent frequencies in the measured signal;

[0031] In this embodiment, the measured signal is a multi-tone signal with multiple frequencies, and the frequency distribution is between 10 MHz and 50 MHz, wherein the minimum difference between two adjacent frequency components is 2 MHz; therefore, the analysis bandwidth B of the frequency domain trigger module is set to 50 MHz, the frequency resolution f0 is set to 1 MHz, the minimum analysis frequency f l is 5 MHz, and the maximum analysis frequency f h is 55 MHz;

[0032] (2) The software end generates n cosine waves corresponding to the frequencies according to the analysis bandwidth B and the resolution f0, wherein the frequencies of the n cosine waves are f l , f l +f0, f l +2f0, …, f h , n = B / f0 + 1, B = f h -f l , f l is the minimum analysis frequency, and f h is the maximum analysis frequency;​

[0033] In the embodiment, based on the analysis bandwidth B = 50 MHz and the frequency resolution f0 = 1 MHz of the frequency domain trigger module, the number n of cosine waves can be calculated as n = 51;

[0034] (3), respectively, the n cosine waves are discretely processed to generate the cosine wave coefficients of each frequency, wherein the jth cosine wave coefficient under the ith frequency is denoted as coe i,j , i = 1, 2, …, n, j = 1, 2, …, kM, k is a positive integer, and M is the number of parallel sampling data in the digital oscilloscope, which is set to 80 here;

[0035] (4), the software end sends the cosine wave coefficients to the coefficient access module of the hardware end;

[0036] First, the software end sends the first M cosine wave coefficients of the first frequency, i.e., coe 1,1 ~ coe 1,M , and then sends the first M cosine wave coefficients of the second frequency, i.e., coe 2,1 ~ coe 2,M , and so on. When the first M cosine wave coefficients of the last frequency, i.e., coe n,1 ~ coe n,M are sent, the software end sends the (M+1)th to the 2*Mth cosine wave coefficients of the first frequency, i.e., coe 1,M+1 ~ coe 1,2*M , and so on, until all the cosine wave coefficients of the frequencies are sent to the coefficient access module;

[0037] As shown in FIG. Figure 2 , the coefficient access module stores the cosine wave coefficients in a matrix form, and stores the first M cosine wave coefficients of the n frequencies in the first row of the storage matrix, stores the (M+1)th to the 2*Mth cosine wave coefficients of the n frequencies in the second row of the storage matrix, and so on. Finally, an X row Y column storage matrix is obtained, where Y = n * M and X = k;

[0038] (5), the calculation module reads the sampling data and the cosine coefficients for direct digital integration;

[0039] (5.1), the measured signal enters the digital oscilloscope for sampling to obtain M parallel sampling data; at the same time, the digital oscilloscope generates an effective signal with a duration aligned with the M parallel sampling data, and the effective signal is transmitted to the coefficient access module as a read enable;

[0040] (5.2), the M parallel sampling data are copied into n parts through a shunt, and then are respectively sent to n calculation units;

[0041] (5.3) In the first clock cycle of the effective signal, the first row elements in the storage matrix are read, and then the cosine wave coefficients coe 1,1 ~ coe 1,M are distributed to the first computing unit, and then the cosine wave coefficients coe 2,1 ~ coe 2,M are distributed to the second computing unit, and so on. n,1 ~ coe n,M are distributed to the nth computing unit.

[0042] When each computing unit receives the M sample values collected in the first clock cycle and multiplies them with the corresponding M cosine wave coefficients respectively, and then sums them up, the sum value S 1,i is obtained.

[0043] In this embodiment, let A i,j denote the jth sample value in the ith clock cycle during the duration of the effective signal; taking the first parallel summing unit as an example, as shown in Figure 3 , the M sample values collected in the first clock cycle are denoted as: A 1,1 , A 1,2 , …, A 2,M , and the corresponding M cosine wave coefficients are: coe 1,1 ~ coe 1,M , then A 1,1 is multiplied with coe 1,1 , A 1,2 is multiplied with coe 1,2 , and so on, and finally the M products are summed up to obtain the sum value S 1,i .

[0044] (5.4) In the second clock cycle of the effective signal, the second row elements in the storage matrix are read, and then the cosine wave coefficients are distributed according to step (5.3) and the sum value S 2,i of each computing unit is calculated, and then the sum values S 1,i , S 2,i are accumulated to obtain the accumulated value S i .

[0045] (5.5) In the third clock cycle of the effective signal, the third row elements in the storage matrix are read, and then the cosine wave coefficients are distributed according to step (5.3) and the sum value S 3,i of each computing unit is calculated, and then the sum value S 3,i is summed with the accumulated value S i , thereby updating the accumulated value S i .

[0046] (5.6) When the valid signal is in its (k+1)th clock cycle, start reading from the first row of the storage matrix again and repeat the above operation until the valid signal becomes invalid and the accumulation ends. Then, update the accumulated value {S1,S2,…,S}. i ,…,S n Input to the trigger module;

[0047] (6) Generate a trigger signal through the trigger module;

[0048] (6.1) As Figure 4 As shown, in the comparator of the trigger module, the accumulated values ​​S are compared. i Comparison with the preset threshold Q i Compare, if S i Greater than Q i If the energy of the frequency component of the measured signal meets the triggering requirements, the comparison result is set to 1; otherwise, the energy of the frequency component of the measured signal does not meet the requirements, and the comparison result is set to 0, thus obtaining a set of 0 and 1 sequences of length n.

[0049] (6.2) The user extracts one or more values ​​from the 0 and 1 sequence according to actual needs, and then performs an AND operation on the extracted values. The AND result is used as the trigger signal. If the AND result is 1, it means that the energy of the frequency components of interest to the user in the measured signal meets the triggering requirements, the target signal has arrived, and a trigger signal is generated. The trigger signal is active at a high level. If the AND result is 0, it means that the target signal has not yet arrived. At this time, the trigger signal is active at a low level and continues to wait.

[0050] Although the illustrative specific embodiments of the present invention have been described above to enable those skilled in the art to understand the invention, it should be understood that the invention is not limited to the scope of the specific embodiments. For those skilled in the art, various changes are obvious as long as they are within the spirit and scope of the invention as defined and determined by the appended claims, and all inventions utilizing the concept of the present invention are protected.

Claims

1. A frequency domain triggering method for a digital oscilloscope based on direct digital integration, characterized in that, Includes the following steps: (1) Set the analysis bandwidth and frequency resolution of the frequency domain trigger module in the software of the digital oscilloscope; Set the analysis bandwidth B of the frequency domain trigger module so that the analysis bandwidth B can completely cover the signal under test. Set the frequency resolution f0 of the frequency domain trigger module. The frequency resolution f0 is less than the minimum value of the difference between any two adjacent frequencies in the signal under test. (2) The software generates n cosine waves with corresponding frequencies based on the analysis bandwidth B and resolution f0, wherein the frequencies of the n cosine waves are f0, ... l ,f l +f0,f l +2f0,…,f h n = B / f0 + 1, B = f h -f l f l For the minimum analysis frequency, f h This represents the maximum analysis frequency. (3) Discretize each of the n cosine waves to generate cosine wave coefficients for each frequency, where the j-th cosine wave coefficient at the i-th frequency is denoted as coe. i,j , i = 1, 2, ..., n, j = 1, 2, ..., kM, k is a positive integer, and M is the number of parallel channels of sampled data in the digital oscilloscope; (4) The software sends the cosine coefficients to the coefficient storage module on the hardware and stores them in matrix form. (5) The calculation module reads the sampled data and cosine coefficients and performs direct digital integration; (5.1) The signal under test enters the digital oscilloscope for sampling to obtain M parallel sampling data; at the same time, the digital oscilloscope generates an effective signal whose duration is aligned with the M parallel sampling data, and the effective signal is transmitted to the coefficient storage module as a read enable; (5.2) M parallel sampling data are copied into n copies by a splitter and then sent to n computing units respectively; (5.3) During the first clock cycle of the valid signal, read the first row of elements in the storage matrix, and then calculate the cosine coefficients coe. 1,1 ~coe 1,M Distribute to the first calculation unit, and assign the cosine coefficients coe 2,1 ~coe 2,M Distribute to the second calculation unit, and so on, to distribute the cosine wave coefficients coe. n,1 ~coe n,M Distribute to the nth computing unit; After each computing unit receives the M sampled values ​​acquired in the first clock cycle, it multiplies them one by one with the corresponding M cosine coefficients and then sums them to obtain the summation value S. 1,i ; (5.4) In the second clock cycle of the valid signal, read the elements of the second row in the storage matrix, and then distribute the cosine coefficients according to step (5.3) and calculate the summation value S of each calculation unit. 2,i Then sum the values ​​S 1,i S 2,i Accumulate to obtain the accumulated value S. i ; (5.5) In the third clock cycle of the valid signal, read the third row of elements in the storage matrix, and then distribute the cosine coefficients according to step (5.3) and calculate the summation value S of each calculation unit. 3,i Then sum the values ​​S 3,i With accumulated value S i Summation is performed to update the accumulated value S. i ; (5.6) When the valid signal is in its (k+1)th clock cycle, start reading from the first row of the storage matrix again and repeat the above operation until the valid signal becomes invalid and the accumulation ends. Then, update the accumulated value {S1,S2,…,S}. i ,…,S n Input to the trigger module; (6) Generate a trigger signal through the trigger module; (6.1) In the comparator of the trigger module, the accumulated values ​​S are compared. i Comparison with the preset threshold Q i Compare, if S i Greater than Q i If the result is 1, the comparison result is set to 1; otherwise, the comparison result is set to 0, thus obtaining a sequence of 0s and 1s of length n. (6.2) The user extracts one or more values ​​from the 0 and 1 sequence according to actual needs, and then performs an AND operation on the extracted values. The result of the AND operation is used as the trigger signal. If the result of the AND operation is 1, it means that the trigger signal is active at a high level. If the result of the AND operation is 0, it means that the trigger signal is inactive at a low level.

2. The frequency domain triggering method for a digital oscilloscope based on direct digital integration as described in claim 1, characterized in that, The method for sending cosine coefficients from the software is as follows: First, the software sends the first M cosine coefficients of the first frequency, i.e., coe. 1,1 ~coe 1,M Then send the first M cosine coefficients of the second frequency, i.e., coe 2,1 ~coe 2,M And so on, after sending the first M cosine coefficients coe of the last frequency... n,1 ~coe n,M Then, it switches to sending the (M+1)th to (2*M)th cosine coefficients of the first frequency, i.e., coe 1,M+1 ~coe 1,2*M This process continues until all cosine coefficients of all frequencies have been sent to the coefficient storage module.

3. The frequency domain triggering method for a digital oscilloscope based on direct digital integration as described in claim 1, characterized in that, The method by which the coefficient storage module stores the cosine wave coefficients in matrix form is as follows: The coefficient storage module stores cosine coefficients in matrix form. The first M cosine coefficients at n frequencies are stored in the first row of the storage matrix, the (M+1)th to the 2*Mth cosine coefficients at n frequencies are stored in the second row of the storage matrix, and so on, until an X-row, Y-column storage matrix is ​​obtained, where Y = n*M and X = k.

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