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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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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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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What is the difference between linear and non-linear filters?
How a mean filter is called as linear filter and a median filter is called as non linear filter? I understand how a mean and median filter operates, but I was not able to relate with the term linear ...
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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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answer
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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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Show others how I hear myself
Sooo .. I've been thinking about this stuff. We all know that we sound different from what we hear of our own voice. It is easy to find out how others hear us by recording oneself and listen to it.
...
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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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Is there any practical application for performing a double Fourier transform? ...or an inverse Fourier transform on a time-domain input?
In mathematics you can take the double derivative, or double integral of a function. There are many cases where performing a double derivative models a practical real-world situation, like finding the ...
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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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2
answers
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How do I determine if a discrete signal is periodic or not?
I want to know how I can determine whether a series of data is periodic or not.
I want to use Fourier transform/series. My data looks either aperiodic
[111100001111000110010101010000101]
or ...
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7
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Why does a longer observation time improve DFT resolution, but repeating a signal does not?
As was proven here: https://math.stackexchange.com/questions/228614/why-doesnt-repeating-a-signal-give-rise-to-a-finer-resolution-of-dft-fft repeating a certain sequence does not improve DFT frequency ...
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Obtain a signal's peak value if it's frequency lies between two bin centers
Please suppose the following:
The frequency of a signal's fundamental has been estimated using FFT
and some frequency estimation methods and is lying between two bin
centers
The sampling frequency is ...
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votes
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answer
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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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Why doesn't sampling a periodic continuous-time signal yield a periodic discrete-time signal?
I have been studying signals and systems lately and I have came across the following claim:
The uniform sampling of a periodic continuous-time signal may not be periodic!
Can someone please ...
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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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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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When Is a Kalman Filter Different from a Moving Average?
this thread asks when a discrete time Kalman filter is better/different from a simple moving average of the observations:
Why use a Kalman filter instead of keeping a running average?
there's no ...
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4
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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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How can I decompose a signal into square waves?
I am dealing with signals that are a superposition of different square waves with different amplitudes and phases. Normally, one would decompose a signal into sine waves with help of the Fourier ...
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What kind of modulation is this?
I'm trying to find out what kind of modulation and encoding is used by my window cover remote control, aiming to implement the same on a Raspberry Pi to add a bit of home automation.
A colleague ...
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6
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DSP programming in C/C++
I have exposure to MATLAB and have some basic exposure to signal processing and plotting in MATLAB... but I am more comfortable with C/C++ than MATLAB because I have been working in Image processing ...
9
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2
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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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1
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What's the similarities and differences between Wigner transform and wavelet transform?
Wigner transform and continuous wavelet transform are both some kind of time-frequency representation of a signal.
What are the similarities and differences between them? Could you give some ...
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Replacing "e" in Euler's formula with another number
Does Euler's formula remain valid if we use any real number other than the constant $e$? For example replacing $e$ with 5 would make the formula look like this: $5^{it}$.
I tried this idea in ...
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4
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the $L^2$-norm of a signal is also applied as its energy!
I am a newcomer in signal processing. I saw that the $L^2$-norm of a signal is also applied as its energy! How is this concept illustrated for those ones who are working in pure math.
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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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Why does signal averaging reduces noise levels by more than $\sqrt{n}$?
I have an electrophysiology signal, which is time-based. It basically measures neural activity in the form of potential differences over time.
The noise in this signal is assumed to be a random ...
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2
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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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Why complex numbers are represents as a+ib and can't be as (a,b)?
I am confused as why do we need to represent the complex numbers with the imaginary y-axis if we can simply represent them as (x,y) ?
I've read that Multiplication by i is an anti-clockwise rotation ...
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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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What are some methods for detecting a sinusoid in noise?
I'm looking for a broad classification on the kinds of techniques available. Something I can use to begin a literature survey.
Some details:
should be feasible for real-time implementation.
Binary ...
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votes
6
answers
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The Least Norm Solution of Under Determined Linear System
Suppose I have a matrix
$$A=
\begin{pmatrix}
1 & 0 & 1 & 0\\
0 & 1 & 1& 0\\
\end{pmatrix}
$$
where the variables are channel information like assume $X_1$, $X_2$, $X_3$ ...
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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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1
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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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Which sections to cover for my graduation thesis on blind source separation?
I'm not sure if I'm on right place to ask a simple suggestion, so please be kind and don't downvote my question. I'm not asking someone to do it for me, I just need short guidance how should I proceed....
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As of 2019, which discrete nonlinear, time-invariant systems with memory are considered "easy" to model and identify?
There are several types of discrete nonlinear time-invariant systems with memory ("NTIM") which are considered "easy" to model and identify. Any such system can be represented using a Volterra series, ...
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3
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Acoustic Scenarios With Negative SNR
For all the practicing engineers out there:
Where have you encountered a negative SNR?
How negative, in dB, was it or estimated to be?
Where would you expect to encounter a negative SNR?
Note: I ...
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White noise DC component
I'm really new to DSP, I'm actually studying Computer Science and took an elective on DSP so my knowledge is pretty limited.
I've learned that pure white noise signal for example has all possible ...
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votes
1
answer
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eigen values and eigen vectors of signal
What does the Eigen values and Eigen vector of a signal or function represent? What is its physical significance? I know about basis vectors of a signal which constitute the orthogonal planes where ...
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How Exactly Does MATLAB Zero Pad Signal?
I am doing some massive number crunching in MATLAB which involves millions of PSD estimations. Each data segment has length 41. So I have been using the multi-taper method with ...
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What's the noise in this signal ? (Beginner question)
There is this raw ECG signal that I have obtained its frequency content in Matlab. The signal was sampled at 600Hz. The following is signal and the frequency content. I want to know what the ...
6
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3
answers
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How can a signal be both periodic and random?
Do any examples of such signals exist where the signal is both periodic and random? Because as I see it, if a signal is periodic then the randomness kinda goes away because you know what the signal ...
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Observation Matrix in Kalman Filter
I've been trying to understand the concept of the Kalman Filter. I came across this great article which makes the concept sufficiently clear.
However I could not understand the concept of the matrix $...
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Simple and efficient algorithm to detect frequency and phase of a sine signal
I need an algorithm to detect frequency and phase of a pure sine signal. The frequency of the input signal changes between 0 and 100 Hz.
The value of the signal gets captured with a frequency of 20 ...
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3
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Is the system $y(n)=x(n^2)$ time invariant?
According to my solution,
$$y(n) = x(n^2) \tag{1}$$
for $y(n,k)$ i.e output for delayed input $x(n-k)$
$$x_2(n) = x(n-k)$$
so $$y_2(n) = x_2(n) = x\big((n-k)^2\big)$$
and for delayed output ...
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Compressive Sensing Incoherence Principle
As people acquainted with Compressive Sensing would know, incoherence and sparsity are two main principles. I've been reading about compressive sampling and developed an interest into the topic. What ...
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Negative values of the FFT
I try to describe a simple signal in the frequency domain with the use of FFT function:
...
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3
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How to derive the results that averaging $N$ signals yields a $\sqrt{N}$-fold increase in signal-to-noise ratio?
If I have understood correctly, averaging $N$ noisy independent segments or signals increases the signal-to-noise $\sqrt{N}$-fold.
How does one derive this result?
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How to Prove a System Is Invertible?
what i know is that for a system to be invertibel it should be one-one ,
but I am confused that if i am given a transfer function of a LTI system how can I prove or verify if it is invertible.
...
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