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WVD cross term elimination method based on affine transformation

A technique of affine transformation and cross-term, applied in the field of WVD cross-term elimination based on affine transformation, to achieve the effect of eliminating cross-term

Pending Publication Date: 2022-02-15
YUNNAN POWER GRID CO LTD KUNMING POWER SUPPLY BUREAU
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  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

After studying the WVD time-frequency distribution of the incident signal and the reflected signal, it is found that there is a large characteristic difference between the self-term and the cross-term of the signal, that is, this difference cannot be directly reflected

Method used

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  • WVD cross term elimination method based on affine transformation
  • WVD cross term elimination method based on affine transformation
  • WVD cross term elimination method based on affine transformation

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0057] The cable is an open circuit two-port network. When there is a structural discontinuity defect in the middle of the cable section, the injected Gaussian envelope chirp signal will be reflected back to multiple signal components, and superimposed with the incident wave properties to form two or more signals with different time differences. . The simulation parameters of the reference signal set in this chapter are: pulse width Ts=0.6us; frequency width bs=5MHz; center frequency f0=5MHz; center time t0=5us; sampling rate fs=100MHz; 8.22×1012; the number of simulation points is set to N=2000; the simulation time T=20us; the reference complex signal s(t) can be obtained; then set the cable length l=200m, and obtain the cable end according to the simulation model of a single non-defective cable The returned reflected signal r(t); the real part of the sum of the incident signal and the reflected signal represents the time domain waveform of the signal, such as figure 2 .

...

Embodiment 2

[0062] In Example 1, simple coordinate translation is difficult to achieve accurate transformation, because the number of points in the image is limited, and the transformed points are misplaced, such as Figure 7 shown. A misplaced matrix will seriously affect the low-frequency filtering in the next step. The energy distribution under different slopes is as follows Figure 9 As shown, the slope k=0.5378 is known, and the affine transformation matrix can be given as follows:

[0063]

[0064] The WVD of the reference signal s(t) and the time-frequency distribution after affine transformation are as follows: Figure 10 as shown,

[0065] For the WVD time-frequency matrix including the incident wave and the reflected wave, there will be cross items, and the coordinate transformation effect under multiple waveform components can be obtained by using the affine transformation matrix to run, such as Figure 11 as shown,

[0066] Affine transformation can adaptively fill an ...

Embodiment 3

[0074] When a local defect occurs in the cable, 3 frequency modulation signals will appear in the time domain waveform, and 3 cross items will appear in the WVD time-frequency diagram. Use the processing steps in Section 4.2 to verify the feasibility of the method.

[0075] Set the cable length to 800m, set the defect position to 300m, and the defect length to 0.5m, calculate the WVD distribution, and then use the method in Section 4.2 to remove the cross item. Since the defect energy is too small, use a grayscale representation. The transformation process is as follows Figure 16 shown.

[0076] Find the time-frequency cross-correlation function with or without cross-terms, where the time-frequency cross-correlation function with cross-terms and the time-frequency cross-correlation function without cross-terms are as follows Figure 17 and Figure 18 shown.

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Abstract

The invention discloses a WVD cross term elimination method based on affine transformation. The method comprises the following steps: enabling a feature difference of a self term and a cross term to be reflected through linear transformation of a time-frequency distribution image coordinate, carrying out filtering processing on data of an affine transformation coordinate system, and finally obtaining WVD without the cross term through reverse affine transformation. The method has the beneficial effects that not only can a cross term be completely eliminated, but also energy of a self term is not reduced at all, that is, a time-frequency resolution of WVD is not affected.

Description

technical field [0001] The invention relates to the field of state monitoring and fault diagnosis of electric equipment, in particular to a method for eliminating WVD cross items based on affine transformation. Background technique [0002] The Wegener distribution is a powerful tool for analyzing non-stationary signals. For common time-frequency analysis methods such as short-time Fourier transform and wavelet transform, the WVD method avoids the use of window functions in the process of signal analysis and processing, and also avoids the problem of mutual restraint between the size of the window and the level of frequency in disguise. It is a method with high time resolution and frequency resolution, and it is also one of the most important time-frequency analysis methods at present. WVD can also satisfy high time-frequency focus and time-frequency edge characteristics at the same time, and its time-frequency resolution can reach the limit of Heisenberg's uncertainty prin...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G06K9/00
CPCG06F2218/06
Inventor 金宇赵威张国志杨进周涛万子逸吴尉民魏敏敏王浩州钱琪杨鸿景闵铁琦张智鑫李晓玲田威
Owner YUNNAN POWER GRID CO LTD KUNMING POWER SUPPLY BUREAU
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