Questions tagged [signal-analysis]
The processing of signals for the purpose of extracting a parameter or property embedded in a signal. Signal goes in and far fewer numbers come out.
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What are advantages of having higher sampling rate of a signal?
Being a non signal processing science student I have limited understanding of the concepts.
I have a continuous periodic bearing faulty signal (with time amplitudes) which are sampled at $12\textrm{ ...
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I and Q components and the difference between QPSK and 4QAM
Both 4QAM and QPSK apparently produce the same waveform, but are they the same mathematically?
In a QPSK constellation, are the mapping points at 45, 135, 225 and 315 degrees while the 4QAM is at 0, ...
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Role of window length and overlap in uncertainty principle?
I am trying to predict epilepsy using spectrograms and a convolutional neural network.
So far I have achieved a validation accuracy of 86% which i feel like is pretty good. Lots of the papers doing ...
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How to check if a signal is power signal or energy signal?
What is the procedure to check the signal type?
example:
$ x(t) = A \sin (\omega t) $
$ y(t) = A e^ {-\lambda |t|} $
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Is deep learning killing image processing/computer vision?
I'm looking forward to enroll in an MSc in Signal and Image processing, or maybe Computer Vision (I have not decided yet), and this question emerged.
My concern is, since deep learning doesn't need ...
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Negative group delay and envelope advance
I am having a doubt reading about delays in signal processing.
Let there be an input to a LTI system with frequency response $H(f)$, given signal $x(t) = a(t)\cos(2\pi f_ot)$, where $a(t)$ is a ...
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Help calculating / understanding the MFCCs: Mel-Frequency Cepstrum Coefficients
I've been reading bits and pieces online but I just can't piece it all together. I have some background knowledge of signals / DSP stuff which should be enough prerequisites for this. I'm interested ...
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Why Does the DFT Assume the Transformed Signal Is Periodic?
In many signal processing books, it is claimed that the DFT assumes the transformed signal to be periodic (and that this is the reason why spectral leakage for example may occur).
Now, if you look at ...
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Shift a signal by fraction of a sample
I have a signal with a sample time of 0.5 micro seconds and I would like to shift this signal by a fraction of the sample time, say by 3 nano seconds.
I have read a few online resources about ...
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Gaussian Equivalent of Convolving an Image 50 Times with a Box Filter
I have a image that I'm convolving 50 times with a box filter, and I like to replace this with a single gaussian filter. Because both box filter and gaussian filter are separable I can just study the ...
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Generalized Cross Correlation
What is the definition of Generalized Cross Correlation?
I need it for estimating the delay (time offset) between two audio signals. The time offset between the two signals might be as large as 500ms....
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Segment/Idenfication of signal from a spectrogram
I have the following Spectrogram of a signal:
Essentially, in this signal, I know there is one point of interest (between 60-80) and between the the particular frequencies.
I could, potentially ...
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GPS signal acquisition
I have a set of GPS satellite signal data, the set is 1 ms long and has the information of two satellites (satellite number, code phase and frequency) buried in noise. This data has a carrier ...
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GPS Coarse Acquisition PRN Codes
Are the actual 1023 bit sequences for each of the 32 GPS satellites available to consumers? I found the IS GPS 200 but it doesn't list the entire sequences. Are verified sequences available for ...
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How do I find the fundamental period of the given signal?
I am having a problem in finding the fundamental period of the signal $x(t)$ given below:
\begin{align}
x(t) &= 2\cos\left(\frac 45 \pi t\right)\sin^2\left(\frac{16}{3} t\right)\\
&= 2\cos\...
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Relationship between energy, power and sampling rate?
Excuse my silly question, but I think the energy increases as the sampling rate increases. In the time domain, the number of samples increases so the energy increases; In the frequency domain, ...
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Meaning of Hilbert Transform
I understand the Fourier Transform which is a mathematical operation that lets you see the frequency content of a given signal. But now, in my comm. course, the professor introduced the Hilbert ...
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Why do we say that "zero-padding doesn't really increase frequency resolution"
Here is a sinusoid of frequency f = 236.4 Hz (it is 10 milliseconds long; it has N=441 points at sampling rate ...
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Calculate and interpret the instantaneous frequency
I'm new to the principle of calculating the instantaneous frequency, and came up with a lot of questions on it. You find them all in a bullet-point list at the end of this text. The text might be a ...
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Duration of unknown rectangular pulse with additive white Gaussian noise
Problem.
There is a discrete signal $f[i]$ (example below).
It is known, that $f[i]$ have a form of rectangular pulse with additive white Gaussian noise.
$f[i] = s[i] + n[i]$,
$s[i] = \alpha(\...
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Magnitude-squared Coherence calculation inconsistence
I have to calculate the magnitude-squared coherence (MSC) between two signal. However, using a routine that uses only one taper (or no tapers at all) my result is always 1, despite the signals are ...
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Random sampling vs uniform sampling
In this paper of Lustig, he speaks about a something which appears unintuitive: sampling at random may exhibit better performance than sampling uniformly. I tried to understand this starting from page ...
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How condition for existence of Fourier transform is valid?
The condition for Discrete time Fourier transform to exist for function $f(n)$ is given as
$$\sum_{-\infty}^\infty |f(n)| < \infty.$$
In case of continuous Fourier transform the difference is ...
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What is meant by *sampling* in terms of the *sampling theorem*?
Let $y:\left(-\frac T2,\frac T2\right)\to\mathbb{C}$ be a square integrable function. The Fourier coefficients of $y$ are $$\underline{Y}(k):=\frac 1T\int_{-T/2}^{T/2}y(t)e^{-i\omega_kt}\;dt\;\;\;\...
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How to calculate the instantaneous frequency of a signal?
I am trying to do the complex trace analysis of a seismic trace in Matlab where I need to calculate the instantaneous frequency of a discrete signal. I have used the formula according to Barnes. I am ...
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Eye pattern construction and interpretation
I have read some text about the eye pattern (or eye diagram), but I do not understand how should I read it.
The wikipedia definition of it is this one:
In telecommunication, an eye pattern, also ...
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IIR Lattice Filter in C programming
I would like to implement Lattice IIR filter in c, i can't defined the value of gN, i know that x(n) = fN(n), but how to initialize gN ?. you can find the algorithm here : n
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understanding discrete-time convolution in LTI systems
I'm trying to understand the discrete-time convolution for LTIs and its graphical representation. standard explanations (like: this one) start with the idea of decomposing an input signal $x[t]$ into ...
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Sampled and aliasing signal
𝑥(𝑡) = cos(200𝜋𝑡) + 2cos(320𝜋𝑡). 𝑥𝑝(𝑡), is produced by sampling 𝑥(𝑡) at sampling frequency $f = 300 Hz$.
Is the signal sampled or aliased and why?
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Frequency Analysis (DFT / FFT) of a Signal Without a Constant Sampling Frequency (Non Uniform Sampling in Time Domain)
I'm a stack exchange user for some time and now I'm registering to ask a simple question (I think!).
I have a vibration signal with an amplitude and time (sampling frequency not constant) in a $...
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Does "keying on" a sine wave at a zero-crossing reduce its bandwidth?
I understand that a pure sine wave of infinite duration occupies no bandwidth, i.e. it is only the modulation of a carrier that gives it sidebands. Does the exact timing of a sudden modulation make ...
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Range-Doppler Coupling in FMCW
I did some derivation of the IF signal of the FMCW using sawtooth LFM.
A chirp with sawtooth LFM is expressed like below
$$x_T (t)=\cos\left(2\pi f_c t + \frac{\pi}{T}B (t-mT)^2 \right)$$
Where, $f_c$ ...
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What is the practical meaning of the variance, covariance, mean value?
What is the practical meaning of variance, covariance and mean for a signal?
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Hartley Transform vs Fourier Transform
Can you explain to me in what way Hartley Transform differs from Fourier Transform? Is it even used today or is it some mostly forgotten, obsolete archaic thing?
Please don't use equations - I dont ...
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Finding the right measure to compare sound signals in the frequency domain
I am comparing the spectral contents of some sound signals with MATLAB. I have quite a few measures but wanted one that represents the centre of gravity of the spectrum.
I used ...
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Is convolution distributive over multiplication?
Is there any formula or expansion for
$$a(t)*[b(t) \cdot c(t)]$$
$$a(t) \cdot[b(t)*c(t)]$$
where $*$ denotes the convolution?
By expansion I mean something like $a(t)\cdot[b(t)+c(t)]=a(t)b(t)+a(t)...
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How to be sure that we chose the correct sampling rate in practice?
Let say I perform an experiment and I record data at a given frequency sampling $F_s$ and then I perform FFT analysis on these results.
As I do not know the characteristics of the perturbation that I ...
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A DFT “periodic inputs” question
Why do people say that the fast Fourier transform (FFT) “views”, or “interprets”, or “assumes” its input sequence is periodic? I ask this question because the activities of viewing, interpreting, and ...
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Proving Nyquist Sampling Theorem for Strictly Band Limited Signals (Whittaker Shannon Interpolation Formula)
I understand that the Nyquist sampling theorem dictates that the minimum sampling frequency, $f_s$, be s.t. $f_s > 2B$, where $ B $, is the bandwidth of the signal. I have read the explanation for ...
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Comparing multiple signals for similarity
I have multiple (between 2 and 100) signals and need to determine when a significant number diverge from the rest. We're exploring machine learning techniques, but we also want tackle this as a signal ...
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Signal Processing using Fourier Transform
How can I derive the fourier transform of
...
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Estimate the Discrete Fourier Transform / Series of a Signal with Missing Samples
Assuming we have a discrete signal $ { \left\{ x \left[ n \right] \right\}}_{n = 1}^{N} $.
Which has a Discrete Fourier Transform / Series.
Now, assume I'd like to estimate its Discrete Fourier ...
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Why do we get ripples in the frequency spectrum of a chirp, and how do I remove it?
The ripples in the amplitude spectrum of a linear spectrum is undesirable. I desire to obtain a flat spectrum response. Hence, how can I remove these ripples? Also, which factors (like time bandwidth ...
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What is the difference between undersampling and oversampling in analog to digital conversion ?
When converting a signal from analog to digital, we observe undersampling and oversampling.
Does oversampling means that the sampling frequency is greater that the signal's frequency and does ...
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Audio Signal Separation - Identifying Interest points
I asked this question here: Audio Separation of .wav signal but it wasn't clear, so, here is my second attempt:
First off, assume that I have a .wav file containing a sentence as follows:
"My name ...
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The normalization of the autocorrelation function and how it changes the definitions you've learned about signal analysis in communication systems
Since this question is book-oriented, I will kindly ask you to accompany it with a book that is considered by many researchers the bible of Digital Communication: Proakis - Digital Communications, one ...
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Dynamic convolution vs Volterra series
I'm trying to understand how a dynamic convolution model relates to something like a Volterra series, and what kinds of effects the latter can capture that the former can't (and vice versa). By ...
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How to alleviate the edging effect of the Hilbert transform?
I am trying to use Hilbert transform to extract the envelope of a residual signal. After implementing the Hilbert transform, I find that envelope jumps very high at its boundaries. May I ask the ...
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Relationship between $E_b/N_0$ and $\rm SNR$ with channel coding
I would like to know what would be the relationship between $E_b/N_0$ and $\rm SNR$ when there is a coding rate of $R_c=K/N$. Normally when there is no channel coding according to this link.
$$\...
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Significance of $ \lambda $ in Basis Pursuit
In basis Pursuit, L1 minimization is done to perform compressed sensing. In the literature there is a $ \lambda $ parameter used as a regularizer.
What is its significance?
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