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Wavelet denoising method based on improved threshold function

A wavelet denoising and threshold function technology, applied in the field of signal processing, can solve the problems of discontinuity, fixed structure, poor denoising effect, etc., and achieve the effect of reducing uncontrollable noise and loss

Pending Publication Date: 2022-06-03
NANJING UNIV OF INFORMATION SCI & TECH
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Problems solved by technology

[0005] To sum up, the existing technology wavelet denoising still has the problem of constant deviation, discontinuity, fixed structure and lack of flexibility and inclusiveness in the threshold function, resulting in poor denoising effect

Method used

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  • Wavelet denoising method based on improved threshold function
  • Wavelet denoising method based on improved threshold function
  • Wavelet denoising method based on improved threshold function

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Embodiment Construction

[0037] like figure 2 As shown, a wavelet denoising method based on an improved threshold function in this embodiment includes the following steps:

[0038] (1) Input noisy signal;

[0039] (2) Select the wavelet basis function, decompose the noisy signal through the wavelet basis, and obtain the wavelet decomposition coefficient w j,k ;

[0040] (3) Estimate the noise variance σ in the noisy signal, and obtain the value of the critical threshold λ;

[0041] The VisuShrink threshold is taken as the judgment threshold, the wavelet coefficients larger than the threshold are reserved, and the wavelet coefficients smaller than the threshold are discarded to realize the denoising of the signal, which has strong applicability. The calculation formula of the λ value is:

[0042]

[0043] where N is the signal length, w 1,k Indicates the high frequency coefficient after the first wavelet transform, and 0.6745 is the adjustment coefficient of the noise standard deviation.

[...

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Abstract

The invention discloses a wavelet denoising method based on an improved threshold function. Noised signals are decomposed through a wavelet basis, and a wavelet decomposition coefficient is obtained; a VisuShrink threshold is selected as a judgment threshold, wavelet coefficients larger than the threshold are reserved, wavelet coefficients smaller than the threshold are abandoned, signal denoising is achieved, high applicability is achieved, a threshold function is improved, and an adjustable threshold function is obtained; filtering the wavelet coefficient according to the improved adjustable threshold function to obtain an estimated wavelet coefficient; and reconstructing the signal by using wavelet inverse transformation to obtain a denoised signal. The adjustable threshold function sets adjustable parameters in the application, and de-noising is carried out on different data systems; continuity and high-order derivation are achieved, and the defect that a hard threshold function generates discontinuity is overcome; the adjustable threshold function well retains the local features of the signal, reduces the influence of uncontrollable noise, and reduces the loss of low-frequency signal information.

Description

technical field [0001] The invention relates to signal processing, in particular to a wavelet denoising method based on an improved threshold function. Background technique [0002] In real life and work, noise is ubiquitous, and noise reduction methods such as finite impulse response filter, infinite impulse response filter and moving average method lead to weak signal correlation after denoising. The wavelet denoising method improves the shortcomings of the general denoising method to filter the signal globally in the frequency domain, and also has the same characteristics in the time domain, and also has the advantages of low entropy, etc., denoising the signal has obvious advantages, so , wavelet denoising has been widely used in many fields such as astronomy, medical imaging and computer vision. [0003] The different stages of wavelet transform to filter noise include: wavelet transform threshold denoising method, wavelet coefficient spatial correlation denoising meth...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G06V10/30
CPCG06F2218/06
Inventor 行鸿彦吴叶丽李瑾
Owner NANJING UNIV OF INFORMATION SCI & TECH
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