A wavelet is a wave-like oscillation with an amplitude that starts out at zero, increases, and then decreases back to zero.
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1answer
25 views
Phase of a signal with multi delayed windowed (rectangular window) signal with different amplitudes
I have a signal $x(t)$ which is composed of multi delayed linear chirps with different amplitudes and phases but they share the same $w$ and $\alpha$, the signal can be expressed as follows:
$$\...
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1answer
23 views
Dimensional reduction from DWT with threshold
I have been trying to find out how can the discrete wavelet transform (DWT) be possible to reduce dimension of data.
Then I saw the question which is seemingly related to my work:
Feature extraction/...
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0answers
10 views
How to select EEG signal band for Dual Tree Complex Wavelet Transform? [closed]
My EEG dataset's sapling frequency is 1000Hz. I want to apply Dual Tree Complex Wavelet Transform for selecting beta band (14Hz to 30Hz) How can i do this?
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3answers
76 views
Denoising a signal
I'm starting hydraulic experiments, where I'd have to measure velocity in an unsteady flow with a device called Acoustic Doppler Velocimeter. In DSP terms, I'd have a nonstationary signal in a shape ...
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0answers
18 views
From Fourier (k space) to wavelet domain in MRI sensing
In compressed sensing MRI (cSENSE MRI) technology the idea seems to entail sampling from the Fourier domain (k space) in a way that, when transformed to the wavelet domain ("sparsification"), the ...
2
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2answers
71 views
Orthonormal Dictionaries for Band Limited Signals
If $\mathbf{x} = [x_0, x_1, \ldots, x_{N-1}]^T$ is the time sampled input signal and $\mathbf{Y} = [Y_0, Y_1, \ldots, Y_{N-1}]^T$ is the Fourier transform of the input signal, then a linear ...
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1answer
23 views
Detection of Troughs and Notches in a PPG Signal
I'm working a project which tries to determine Blood Pressure from PPG signals.I'm trying to extract the features as shown below...
I'm having problem in finding the troughs and dicrotic notch for ...
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0answers
22 views
signal denoising by continuous wavelet transform
i want to use Morlet mother wavelet for signal denoising so i should employ cwt only. Is there any proper MATLAB code for this target?
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0answers
55 views
How does the Scipy implementation of CWT actually work?
I'm trying to use the SciPy implementation of the Continuous Wavelet Transform to analyze EEG data.
I am using The problem is that I have no idea what the width parameter should be. It says that it's ...
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0answers
41 views
How to interpret Discrete Wavelet Transform Coefficients?
I want to extract features from DWT coefficients like Power Spectral Density, Max frequency, Min frequency etc.
After taking DWT, we get coefficients D1, D2, A2 etc. But my question is, Are D1, D2, ...
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0answers
52 views
Wavelet transform and FFT using to extract feature power bands with EEG signals
I am using 5 channels [ fz , cz , c3 , c4 , pz] to detect drowsiness of driver
My First Question is, what is the right input to get feature power band ( Theta , alpha , gamma , beta ) to wavelet ...
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0answers
12 views
Do the magnitude of the signal changes in the wavelet filtering
I am using Daubechies 4 wavelets to extract a required signal.
In my signal there is a magnitude change. My raw signal lies from $-3$ to $3$, but when I choose the detail coefficients of the Db4 ...
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1answer
31 views
Isolating frequency-specific oscillation from transient
I am performing time-frequency analysis on electrophysiological data with complex morlet wavelets. Each decomposition in the attached figure shows total power following the onset of a stimulus (top ...
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0answers
24 views
Determine scales for continuous wavelet transform (cwt) obtained
How to obtain the corresponding scales for frequencies while computing cwt in Matlab or any other formulae?
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0answers
23 views
Does a “chirp”-like generalization of the Gabor or Morlet wavelets definitions exist in the lit somewhere?
I have asked this at the Math SE also.
Predicating this on the definition of the continuous Fourier Transform preferred by most electrical engineers:
$$ X(f) \triangleq \mathscr{F} \Big\{ x(t) \Big\}...
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10 views
Wavelet central frequency
What is the definition of the central frequency of a Wavelet and the bandwidth of a Wavelet? How do they affect the resultant waveform of the wavelet?
Thanks.
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0answers
32 views
Algorithm Question for Haar Scaling Function and Discrete wavelet transform
Let $\displaystyle f(x)= \begin{cases} 4x^2-4x+1 & 0\le x\le 1, \\ 0 & \text{otherwise}. \end{cases} $
a) Find the approximation $f_{-3}$ of $f \in V_{-3}$ using the Haar scaling function
...
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0answers
138 views
Plot CWT (Continuous Wavelet Transform) in 3D using Python
I am working on a project using signal processing.
Part of my work is to apply the CWT on the signal I have.
As I read, that I can plot the signal in the frequency-time domain using CWT.
So my ...
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0answers
12 views
Implementing Wavelet family matrices
I want to use CS to reconstruct an image from fewer samples, and I would like to use wavelet coefficients but I don't know how to define them when making a Psi matrix.
I have written wavelets ...
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0answers
7 views
Wavelet Quality factor
I read in my lectures that a wavelet should have a constant quality factor Q but without any explanation. Can anyone please explain what do we mean by a quality factor. Thanks..
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1answer
37 views
Can I apply CWT on a digital signal?
First, I am so sorry for my dumb and stupid question, I am very beginner with signals.
Say that I have an ultrasonic sensor cabled to an ADC (Analog to Digital Converter).
The ADC converts the analog ...
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0answers
21 views
Daubechies orthogonal Wavelets
I read a document that it said: "Daubechies orthogonal wavelets D2-D5". Then I've searched on the Internet to get information about this kind but I haven't found any information about it. Moreover, to ...
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0answers
20 views
Qrs complex detection using haar wavelet
I am using this algorithm to detect QRS complex from ECG signal that is samled at 360Hz that is decomposed to level 5 with haar wavelet
In the fourth step it says that the duration of the QRS ...
1
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0answers
17 views
why is my inbuilt function is not matching with the db5 CA and CD coefficients generated by my code
I am working on wavelet decomposition.As read by the theory i have implemented wavelet decomposition in MATLAB. CA and CD for wavelet decomposition of db1 matches with the inbuilt function but not ...
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1answer
32 views
Alternative function for Matlab Stationary Wavelet Transformation
I'm currently working on a project of mine where I have to use stationary wavelet transformation. I found a perfect way to do the transformation using wavelet toolbox of the Matlab. But since it is ...
1
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0answers
48 views
How to define the scales in a biorthogonal, dyadic Discrete Wavelet Transform in Python
I am sorry if this has been discussed before but I could not find any answer.
I am trying to implement an algorithm that I found in a paper which asks for a biorthogonal, dyadic DWT with scales 1 and ...
3
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0answers
44 views
wavelet reconstruction
I am doing mtech project now.
Actually I am working on discrete wavelet transform.I have done till wavelet decomposition. I have been stuck in reconstructing the signal back to original .please help ...
1
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2answers
114 views
How to implement a filter associated to a specific wavelet
I am working on ECG signals, to eventually extract features in order to detect an arrhythmia and classify it.
I am using Discrete Wavelet Transform with biorthogonal wavelet bior6.8
During my research,...
2
votes
2answers
140 views
How to extract features of individual spikes in non-negative signal?
I have data of non-negative (in the sense there's no signal below baseline) spiking waveforms, which are in the form of a 1D array of numbers:
Spikes that cross some threshold are considered real ...
2
votes
3answers
95 views
Denoise techniques when clean signal and pure noise is available
I have the clean version of the signal.
I can obtain the environmental noise.
I want to apply an effective denoising technique on a noisy signal (i.e., clean plus environmental noise).
Some ...
1
vote
1answer
73 views
What the entropy equations mean?
In wavelet packet image compression, different types of entropy methods can be used, like Shannon and log-energy.
Shannon entropy uses this equation $\mathrm{ent}= -\sum (x^2 \times \log(x^2))$, ...
1
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0answers
85 views
Log energy and Shannon entropy?
For best tree decomposition using wavelet packets, i have tried both Shannon and log energy entropy functions. I noticed that log energy leads to images with higher PSNR values. Could you please help ...
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0answers
487 views
Applying a wavelet transform to a 1D time series
I'm preprocessing a non-stationary financial time series as input for a machine learning algorithm, and I'm trying to reduce noise in my data. All the research I've looked at points towards wavelet ...
3
votes
0answers
57 views
Selection of transforms, windows, wavelets for current signal analysis
I am new to this topic but I already read about the propperties of different signal analysis methods. I am stuck with the obvious advantages of FFT, STFT and Wavelet transforms but can't find good ...
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0answers
245 views
Calculating and plotting Wavelet Power Spectral Density
I would like to calculate the power spectrum of the wavelet coefficients for an observed signal and compare it with the Fourier power spectrum of the same signal. I want to do this to show how the ...
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votes
0answers
8 views
Obtaining a fixed number of wavelet coefficients from variable-length inputs
I recently discovered wavelet transforms, and have studied some work done using them to create (meta-)features for machine learning classifiers. However, all the work I've seen thus far uses images/...
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0answers
33 views
Daubechies Transform Example on Integer Array
I'm very new to wavelet transforms and I've had difficulty in finding examples that do a good job illustrating the steps clearly enough for me to turn those steps into code. One of the best sources I'...
1
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0answers
747 views
Discrete wavelet transform: visualizing relation between decomposed detail coefficients and signal
I'm trying to directly visualize the relation between discrete wavelet transform (DWT) detail coefficients and the original signal/its reconstruction. The goal is to show their relation in an ...
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0answers
28 views
I want to understand the Dual Tree Complex Wavelet Transform
I want to understand the dual tree complex wavelet transform for vibration analysis of motor faults.I search a lot of books and materials but couldn't understand
Can anyone recommend me a book or ...
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1answer
47 views
Wavelets and bank filters
The wavelet transform has a problem as it gives poor time resolution for low frequencies and poor frequency resolution for high frequencies according to uncertainty conditions.
This appears well ...
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0answers
57 views
Frequency Response of MODWT Filters at Various Scales
I am trying to find the frequency response for wavelet filters -- specifically MODWT wavelet filters at various scales (for scales 1, 2,3, 4,..).
Given a MODWT filter at Scale 1 (Daubechies 4-tap):
...
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votes
1answer
36 views
Question about normalization before estimate the spectrum
I work with a Electrophysiologist Team and i have seen something who interrogate me (i'm a noobs in DSP).
They acquires a signal into a brain structure (an LFP to be precise) :
in a first time they ...
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0answers
17 views
continous wavelet transform
continous wavelet transform gives better resolution or not i'm facing the problem here, i generated a sine wave which shown below. Having the frequency components i.e.,2000 hz and 800 hz.
And I have ...
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0answers
21 views
How can one obtain a “local” Fourier transform from a discrete wavelet transform?
Is there a certain wavelet transform that one could perform globally that would allow one to calculate a local power spectrum at any point in time? This is for a discrete data set.
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0answers
173 views
How to implement real time wavelet transform
I have a real time system where incoming data rate is 512 Hz. This signal needs to be filtered in real time. My algorithm has a mix of wavelet filters and FIR filters.
During my algorithm development, ...
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votes
0answers
45 views
Wrapped vs Unwrapped Phase Signal in Image
After a wavelet transform, you could easily get the phase of an image by atan2. Usually the phase obtained is wrapped between $-\pi$ to $\pi$, and for a noise-free ...
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0answers
30 views
Delay compensation in wavelet decomposition
I am working on wavelet based ECG delineation and I'm trying to implement the algorithm developed by J.P Martinez.
I'm applying a quadratic spline wavelet and using the atrous algorithm(using the swt ...
2
votes
1answer
150 views
Making sense of Haar transform and inverse Haar transform
Yesterday, my teacher taught us about the Haar transform (for pictures). We had to implement it in Python and when I finished I was wondering: what was the point?
I can't explain the purpose of what I'...
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0answers
60 views
Phase Shift in Image Processing: Some Questions about Local and Global Phase
I'm trying to clear my head about the phase shift I have read on academic papers and online. As we all know, the phase of an image could be obtained via many methods, two commonly used is Fourier ...
1
vote
1answer
38 views
Integer Wavelet with Only Positive coefficients
Is there any Integer Wavelet Transform which produce only positive coefficients?
Currently i'm using Haar wavelet but it produces both positive and negative coefficients.
