# Tagged Questions

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### Confusion with regards to units in Sinc pulse

I am currently reading a section in the Handbook for MRI Pulse Sequence book where it says that the time-bandwidth product for a SINC pulse is given by: $$T \Delta f = Z$$ where $T$ is the length ...
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### fscanf (filepointer, “%d\n%lg\n”, sig_length, sample_rate); how to interpret it? [migrated]

I have an audio format conversion from an audio format that predates the internet, it's from the get_signal() function on this page, i don't know how the sample values are formatted and why i need the ...
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### Is this graph of Wigner-Ville distribution OK?

I am studying some code for smoothed Wigner-Ville distribution. update 3- solution, graph was over amplified in a 2d overdrive/oversaturation effect. if i divide by 20 only a line is visible. Update ...
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### Application of the gabor limit to a time-frequency analysis

I want to do a time-frequency analysis for a signal containing several sinus signals with a frequency between $400\,\text{Hz}$ and $800\,\text{Hz}$, each with a frequency separation of $\Delta f$. The ...
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### Does MATLAB have a FM discriminator [closed]

I'm wondering if MATLAB communications or DSP toolboxes has a FM discriminator? If so, what is the name of the function/object?
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### Equalizers for controlled ISI and ICI

I am new to the physical layer and may not have all the necessary background. I have the following question on the design of Equalizers. Equalizers to combat the effect of ISI and ICI due to ...
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### Extract the frequency range/mean from time series using Wavelet

I am working with Wavelet for the first time, and I need your help. I have time series of velocity collected for 2 min at 32 Hz: x = [n] where n = 120 (sec)*32 = 3840 counts. I am using Morlet ...
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### Lowpass filter impulse response in frequency domain

A Linear Time-Invariant system with impulse response $h_1[n]$ is an ideal lowpass filter with cutoff frequency $\omega_c =\pi/2$. The frequency response of the system is $H_1\left(e^{j\omega}\right)$. ...
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### Wavelet transform of time series(PyWavelets)

I am a newbie in wavelet transform and I would be glad if you help me. I have different time series(ECG with rate = 1000 points in second, length = 100 000 points). I need to classify them in two ...
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### Matlab signal processing removing white noise from signal

What is the way to address the removal of white noise from a signal? Extra Details Hi I also agree the details are as follow: ...
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### How to find the energy of a single frequency from its time-frequency distribution?

I have a non-stationary time series. I am interested in finding the energy content of a single frequency (actually the ratio of that single frequency over the total energy of the signal). The problem ...
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### How does shifting a signal in the time domain affect its frequency domain?

Suppose the signal is shifted by dt (signal 'starts' later, say after 1s instead of 0s), does that correspond to a positive or a negative phase shift df in the frequency domain? There are certainly ...
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### Multidimensional EMD - Problem Plotting Spectogram

I'm having difficulty plotting the famous Time vs Frequency plot of the Amplitude. What I did so far is  1. Simulated a three dimensional signal using ...
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### Getting frequency content at different times from discrete wavelet transform coeffs

After being away from DSP for a long time, I am trying to familiarize myself with wavelet transform. Here is what I (think) have understood so far: Wavelet transform provides you high time ...
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### How does the Magnitude of an FFT relate back to the Time Series wave it was created from?

Alright, to start out I am a mechanical engineer with very little circuits and digital signal processing background. So please excuse my ignorance as this is far out of my usual territory. When ...
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### Find time lag between two time series

I am trying to find the time lag between two time series over t = [0,1000] using MATLAB (not that it matters). The first time series is simply t^2. The second is (t-15)^2 which is, of course, shifted ...
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### Is sub-sampling delay estimation possible without interpolation?

I want to estimate time delay between two complex narrow band signals. I can use any correlation method. There are several methods in the literature about sub-sample time delay estimation. Generally ...
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### How can I accurately represent an mp3's wave form in respects to time?

I'm trying to programmatically plot a sound wave that I have placed in a 2d array, however, I cannot consistently get the sound wave to reach the end of the window. For example, when you load a sound ...
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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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### Spectrogram, time vs frequency localization, and length of signal

So I'm having some trouble conceptually and am hoping somebody can clear something up for me. This is long and I apologize for that but I want to provide as much information as possible so that the ...
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### How to properly explain that computing wavelet at fine scale reveal localized high frequency component

I wonder if it is fair enough if I try to follow "Wavelet Tour of signal processing" which apply the Parseval formula:  Wf(u,s) = \langle f,\psi^{u,s}\rangle = \int f(t) \bar{\psi}^{u,s}(t)dt = ...
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### Time-Frquency Resolution issues

While Im studying wavelet transform, I have this questions in my mind which can't find it's answer: I understand that when we take longer time windows and take the fourier transform we would suffer ...
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### EEG Power at specific time points

I'm in the process of building features for an EEG machine learning problem and have been doing some reading about what features may be useful. Turns out, that alpha band (8-12Hz) power can make a ...
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### Python - time frequency spectrogram

I have some 64 channel EEG data sampled at 256Hz and I'm trying to conduct a time frequency analysis for each channel and plot a spectrogram. The data is stored in a numpy 3d array, where one of the ...
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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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### Defining an average in time for a density in time

I'm reading the text book "Time-Frequency Analysis" by Leon Cohen and I've made my way through a decent portion. There is however a conceptual issue I keep coming back to. The book states: If we ...
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### How to find a certain frequency in a signal that varies in time?

I have an EEG signal. It is amplitude verses time. I want to find out how certain frequencies in that signal vary with time. One way I think I can do this is to do a short-time-Fourier-transform on ...
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### 2 points and instantaneous phase sufficient to estimate amplitude and frequency of sinusoid?

If you have 2 points (x1y1,x2y2) in a Cartesian grid, there are an infinite amount of sinusoids that pass through them. But if you are also given the instantaneous phase (Th0) in radians or degrees at ...
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### How would I go about designing a difference equation for a given type of filter?

I have experience using design tools such as Xilinx's CoreGen and MatLab's DSP tool kit, but I have not really had much experience designing filters from the ground up. Reinventing the filter as it ...
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### Teager-Kaiser Operator vs. Hilbert Transform

Since a couple of months I started working on the extraction (estimation) of signal frequency and amplitude components by means of two different time-frequency approaches, namely the Hilbert transform ...
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### Signal Sampling

I am new in this field (junior year) and I have a question may a little lazy for the majority of the forum. I have a speech signal $x(t)=0.4\cos(100πt)+0.3\cos(1800πt)+0.2\cos(980πt)$ and I know ...
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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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### What is a 'time-variant' signal?

I have found in the literature a "time-variant signal" term , but I could not understand what that's mean. I know that there is "time-variant systems", but this is the first time, which I see a ...
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### system response: time vs frequency. Why do I get different magnitudes?

I am simulating a linear system described by the following equation $m \ddot{x} + c \dot{x} + k x = A \sin(\omega t)$ ...
217 views

### Get data ready for IFFT

I am having troubles applying the IFFT function to some data I have. I already had a look here Complex conjugate and IFFT and here What assumptions should be used to invert spectrum into time domain ...
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### Time Frequency Signal Analysis in Mathematica (MMA)

I want to know " Whether there is any Tool Box in Mathematica (MMA) for the Time-Frequency (TF) Signal Analysis". I am well-versed in MMA Programming, so want to do TF Signal Analysis in MMA. I think ...
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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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### 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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### 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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### Introduction to Clustering and Classification of Linear Sequence

I'm a programmer/engineer that is getting into developing prototype wearable technology. I would like to be in a position to interpret raw accelerometer data and categorised the data into activities ...
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### Does Wigner-Ville distribution provide the highest resolution?

For linear time-frequency representation, the resolution is limited by Gabor limit. However, if interference is allowed, the resolution may be higher. What is the possible resolution in such a case? ...
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### 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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### 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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### Is Gabor uncertainty a feature of the Fourier transform, or of nature?

By Gabor uncertainty, I mean the principle of uncertainty as applied to signals — with the result that you can't have arbitrary time and frequency localization. By way of background to my question, ...