Questions tagged [time-frequency]

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Plotting a scalogram of a signal's Continuous Wavelet Transform (CWT) in python

So I've been learning about wavelets for a few weeks because I'd like to use them in a research project I'm working on and I've been trying to grasp the general ideas behind them.I've been struggling ...
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Reconstruct signal from its Spectrogram only

The spectrogram of a signal throws away the phase information, but it is said to be possible to reconstruct the signal only from the spectrogram [1] via $$s(t) = \frac{1}{2\pi s^*(0)}\int_{-\infty}^{\...
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Interpretation of instaneous time and instaneous frequency in time-frequency plane?

In this paper: Sparse time-frequency representations, Given signal $x(t)$, the time-frequency representation was got by Gabor transform and was denoted by $\chi(t,\omega)=|\chi(t,\omega)|\exp(\mathrm{...
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Hints and helps to implement an accurate wavelet packet transfrom

I want to implement a Time-Freqency analysis by wavelet packets. I don't know what level and sampling rate should I use. I've tried different value for level(3,4,5,6,). but I couldn't get an accurate ...
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Instantaneous Frequency Estimation by Hilbert Transform - Theoretical Justification and Proof

I would like to better understand why the instantaneous frequency estimation by Hilbert transformation works (and especially why it doesn't work / lead to precise results in many cases). The ...
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Does anyone recognize this modulation?

I'm trying to extract the code of my garage remote, but i have some difficulty to find witch modulation has been used. At first I thought it was a simple digital modulation, but there is some strange ...
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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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How to derivate in the frequency domain

I have two Time Domain functions, $f_1(t)$ and $f_2(t)$. I have both Fourier Transforms, $F_1(\omega)$ and $F_2(\omega)$. Functions $f_1$ and $f_2$ are not independent and, in fact, $f_1$ is also a ...
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Vibration signal analysis of non-stationary movement

my task is to develop a condition monitoring system of a machine module. For that I am using the vibration sensors placed on the machine housing. I want to focus on only one module of the machine, a ...
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2 votes
1 answer
236 views

Does the instantaneous frequency contradict the uncertainty principle?

The uncertainty principle states that there is a trade off between time and frequency. So, finding frequency components at specific time is impossible. However, the instantaneous frequency measure the ...
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Why does using a log scale ruin (warp) my scaleograms?

I'm trying to make a scaleogram of neural data using the continuous wavelet transform (with Morlet wavelets). As a starting point, I use just a simple sine wave built from two frequencies, 50 and 80 ...
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How to restore time domain signal after multiply cosine signal when cosine signal has unknown initial phase?

I use AD9954 as cosine signal generator,then use ad835 to multiply this cosine signal with antenna signal. As ,the antenna signal frequency shifted after ad835,then ...
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Estimating Average HR from PPG sensor

I am reading Smartphone based Blood Pressure Monitoring via the Oscillometric Finger Pressing Method, which is trying to estimate blood pressure from a PPG sensor and a small applied force finger ...
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Time spans in coherence computation

Currently I'm writing my master thesis and I'm having troubles with coherence definition. My question is similar to https://stats.stackexchange.com/questions/92412/clear-steps-to-calculate-coherence-...
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Bandpass filtering with passband changing with time

Is it possible to implement some sort of filter which adapts as a function of time? Specifically, say I have a "noiseless" model of some signal which has the same frequency components at the same ...
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302 views

Power spectral density of a pulse

A little background: I am simulating the response of an antenna to a pulse. The pulse has a wide frequency range, but the antenna only responds to a fairly narrow frequency. I can extract voltage and ...
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232 views

How to sample a transfer function (angular spectrum) in the frequency domain?

I am having this problem in Fourier optics, where I am using the Angular spectrum method (a lti filter) to calculate the electric field at the required plane given ...
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For extracting the characteristics of the signal what minimum duration should be considered?

Being non signal processing student I have a limited understanding of concepts. I have a continuous periodic bearing faulty signal of 10 seconds duration sampled at 12 kHz. So I have 120,000 ...
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Feature recognition within a single song

I want to write an algorithm in C++ which is capable of identifying specific features within a single song, e. g. the sound of a drum which is played 100 times during 5 min. State of the project So ...
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Dividing a signal in channels

I have a signal in time domain, and I have to convert it into frequency domain and divide it into 100 channels, and find the center frequency of each channel. I am not good in "MATLAB" so how to do ...
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Time-frequency analysis

I had this question in the exam without any further explanation. Why the time translation invariance is an important feature for time-frequency distributions? I am writing to ask whether anyone can ...
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How can I get frequency information in wavelet?

I am working in image processing. I am confused while getting into wavelet. I applied the fft2() function on Lena image and I got frequency information for the same. But when I applied bior4.4, a ...
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Heisenberg boxes image for Matching Pursuit

I'm using the MATLAB algotirhm Matching Pursuit to obtain the Gabor atoms forming a signal. But now I want to graph them in a "Heisenberg boxes" graph. Does someone how if is there a function to graph ...
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Estimating The Time-delay using the Phase of the Cross- Correlation function

I am relatively new to time delay estimation. I am working on a project where I am estimating the time-delay from the phase of the cross-correlation function (CCF), since it is more reliable in ...
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483 views

Correct way to implement Discrete and Stationary Wavelet Transform?

Can someone please confirm if this is indeed the correct way to compute DWT: ...
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1 answer
307 views

Variance of the Discrete Gabor Transform for practical implementation

When we design a discrete Gabor filter for a 1D signal, how do we determine the variance of the filter, depending on the time step of the signal? Is there any empirical theorem/result that we should ...
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overlap and save method) relation zero padding with double size FIR filter coefficient

i'm doing overlap and save method at frequency domain to do this, i added one block back and forth at filter and signal respectly The problem is my filter is bessel function and that is look like this ...
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Gabor uncertainty and time-frequency resolution

I have a question about Gabor's uncertainty theorem, and how it relates to time and frequency resolutions. As I understand it, Gabor's uncertainty theorem states that the standard deviations of a ...
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Estimating significance in time-frequency spectrograms

I want to investigate the common input of two EMG signals using a wavelet-based approach. To this end, I chose the continuous wavelet transform to approach my research question. In addition, I would ...
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Problem with creating wavelet transform

I am trying to create time-frequency representation of my brain signal. I would like to create the data for frequencies from 0hz - 120hz (so it can cover, delta, theta, alpha, beta, low-gamma and high-...
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40 views

How to use tfa.image.sparse_image_warp?

I have the log mel spectrograms of a few audio clips and I am trying to augment the spectrograms using tfa.image.sparse_image_warp so that time warping can be achieved as done in Google's SpecAugment. ...
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48 views

filtering large wiggles in signals

I am trying to filter out large wiggles showing in a signal. Those wiggles are happening due to many signal processing layers and a final sine Fourier transform (no phase) Here's the python code i am ...
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How to interpret a break in linearity when performing detrended fluctuation analysis?

I have time series with 1048 values and when I perform detrended fluctuation analysis on this time series (using the windows or scales of 2^4 to ...
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Reconstructing signal from frames

Edit: Please treat code here as python-esque pseudo-code; it would syntactically fall closest to MATLAB or Python+numpy+scipy users. If I have a signal in frames, and I want to put it back together - ...
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Calculating the spectrogram of the center of pressure time series in human standing balance

I have some biomechanical data of a few subjects standing on a force plate. The center of pressure along the x and y axes was measured. The total time of measurement was 30s and the sampling frequency ...
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Varying speed of shaft Spectral Kurtosis

I want to perform Spectral Kurtosis (Kurtogram) on 10-second vibration signal of 25.6 kHz sample rate, where the shaft is varying in speed. Will a preprocessing step of resampling the signal be ...
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Time Frequency bin

I am doing research in audio signal processing for DOA estimation. I came across the term Time-Frequency bin. I have gone through several articles but none of them specify a TF bin rather it specifies ...
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How to tell, which coefficient corresponds to which frequency while computing wavelet transform?

I am applying wavelet transform on functional Near Infrared Spectroscopy (fNIRS) signal. My aim is to get the info that which coefficient corresponds to which frequency in the signal. Is it possible ...
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CWT coefficients as features for ML algorithms

I use CWT coefficients as features in ML algorithms and then I did the feature selection using the chi-square test but recently I figured out that the chi-square test can only be applied for ...
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How to choose notch frequencies for filtering line noise?

I'm using the function to filter out line noise at 60 Hz (and 120, 180 Hz) caused by electrical noise: ecogNotch In the case below I can effectively filter out the line noise with a notch filter at ...
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130 views

Any examples of analysis in time domain to extact information

I am sending a 20Khz signal from my phone and capturing all the signals while doing exercise above it. Here I have a signal of a person doing "hand scissors exercise" I am doing analysis on how many ...
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How accurate is Wavelet packet decomposition for emg signals with frequencies from 10 to 40 Hz?

I have an electromyographic signal sampled at a frequency between 10 and 40 Hz in a time window of 300ms. Is wavelet packet decomposition adequate in order to perform features extraction for ...
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Variation of Pulse width with center frequency in Pulse Compression technique

Assume a chirp with BW = 1 Hz (frequency range 0-1 Hz) for a period of 700 sec. The pulse compression technique (obtained through auto correlation function) applied on the chirp generates a pulse ...
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pattern recognition in a time series

I understand that the question I am asking seem the be somewhat related to another question which has been asked already. But I feel that this is an entirely different question. I have a huge (over ...
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For discrete signals, why does phase change not correspond to time shift?

I'm going through a Signal Processing lecture where the professor mentions this fact and the argument given is: Suppose you have a sinusoidal signal: $Acos(\omega t)$ Now if you change the phase of ...
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272 views

Frequency and time marginals of STFT and Wigner-Ville Distribution

I want to compare time and frequency marginals of Wigner-Ville distribution and STFT. I can calculate WVD's marginals by simple sum operation since WVD is real. But I could not figure out how to deal ...
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Fast Fourier Transform and Clustering of Time Series

I'm making a project connected with identifying dynamic of sales. That's how the piece of my database looks like: There are free columns: Product - present the group of product Week - time since ...
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287 views

Algorithms for removing oscillations?

I am interested in removing oscillations from a signal to capture the lower-frequency variations, similar to the objective of this problem. The oscillations vary in frequency in the time domain, so ...
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TDOA using demodulated signal

Is it possible to find time delay of arrival using demodulated signals (of bandwidth ~200hz)? I have a setup in which I receive (multiple receivers, of course) modulated signal from a source. I want ...
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Time of sound-signal

Let's say I have a sound file, I then compute the Spectrogram and segment each part of it. Assume that it is a recording of someone saying the word "Hello" and therefore, each piece is given like so: ...
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