Questions tagged [signal-processing]
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34
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Spectral Intensity of complex signal
I'm simulating an electromagnetic wave that has a real and imaginary part. Something like:
$$ E(x,t) = A(x,t) e^{-i(\omega t - k x)} $$
Where $A(x,t)$ is some complex amplitude. Then taking the ...
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Fourier Transform with logarithmic spacing?
I have a very long time series $f(t)$ (hours) dataset taken at a very high sample rate (250 MHz) and would like to understand its frequency structure at many different frequency scales (from milli-Hz ...
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Calculate the time taken to run an algorithm on GPU
I want to calculate the total time taken for a fixed code run using an NVIDIA GPU (for instance, Tesla K40). The code has to run 1 million single-bit comparisons. All the comparisons are independent ...
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Deconvolution of sinc function in spectrum calculation in FTS
In Fourier transform spectroscopy (FTS) I am calculating a broadband interferogram (e.m. frequency 190-300 GHz top-hat), then back-retrieving the spectrum by FT.
Here in the figure, you can see the ...
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Digital beamforming: how payload manipulation can change beam direction without manipulating the carrier?
I'm interested in how digital beamforming works and I can not find an answer for a lot of time.
I googled, asked teammates, and couldn't get it.
Let me describe my question.
From my understanding, the ...
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Fast evaluation of trigonometric polynomials
Suppose you have a trigonometric polynomial of the form
\begin{equation*}
x(t) = \sum_{k = 0}^N a_k \cos(2 \pi k f_0 t).
\end{equation*}
Using Clenshaw algorithm, one can evaluate this polynomial in $...
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Cauchy Lorentzian simulation on FFT with oscillation
Recently I do simulation on Lorentzian Function with FFT
Lorentzian Function is 2a/(x**2+a**2)
...
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Is the sine function periodic in $x$ or $y$?
I know sine is $2\pi$-periodic, but some people say the motion is "periodic in..."
Would it be periodic in $y$?
If we move along the $x$-axis, the function values $y = \sin(x)$ will repeat, ...
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Solving numerically a linear ODE
I start by saying that I do not have a strong background in numerical analysis, so I may miss some basic things or make trivial mistakes.
Motivated by some problems in digital signal processing, I ...
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Filtering out outliers in a vector field [closed]
I have a vector field that represents a incompressible fluid flow (ie. divergence-free, ideally) that contains a certain percentage of vectors that are completely incorrect, due to the procedure used ...
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Normalising DFTs Correctly
I have been playing around with convolutions in scipy's signal package:
...
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Live audio processing using c++ (standard or external libs 'ue4')
My goal is to get audio from the input of another device (either connected to computer throught aux or audio interface threw rca or coaxil(from an external device playing audio live) adapters to line ...
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Fast convergence of smoothing of periodic noise
I have essentially periodic data from a simulation (not exactly periodic but is qualitatively fairly periodic), and I'd like to take an average or noise filter of some sort that I can get a well ...
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Find shift in high resolution noisy signal if only local argmax data are available
Let's say I have a signal which consists several pulses of approximately equal height, and I have to correlate it with the expected positions of the peaks to find the shift of this signal w.r.t. a ...
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332
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identifying peaks in data
I have data with peaks on some background, for example:
The two prominent peaks at ~390 and ~450, as well as the much smaller peak at ~840. What are some options to programmatically find the position ...
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445
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What does the Jackson Kernel measure?
A certain filter I'm writing uses two different kernels. The Fejer kernel (which is common) and the Jackson kernel:
$$ \Delta_T(x) = T \,\left( \frac{\sin \pi T x}{\pi T x}\right)^2 \quad\text{and}...
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Cyclic Deconvolution
Suppose I want to generate a vector y which when circularly convoluted with a vector h gives me a vector ...
Abhi
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Can Mallat's pyramidal algorithm be extended to non-power of 2 input sizes?
Mallat's pyramidal algorithm for the discrete wavelet transform operates on power-of-2 vector lengths. Can it be extended to work on inputs of any size without resorting to zero padding?
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Which technique to use for signal/image processing or noise removal?
I have an image that looks like this (it might appear low res in a browser because it is 16 MB). This image was taken with a scanning electron microscope, but because the equipment is outdated there ...
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Is the inverse radon transform considered a linear operation?
I wanted to know if practically the inverse radon transform operation is considered linear and would be a good candidate for the application of compressed sensing. To my understanding it should be ...
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Hankel transform from paper works only for certain functions
I implemented an algorithm for solving the Hankel transformation based on a paper. My problem is: It works very good for the functions suggested in the paper (as test functions), it works pretty ok ...
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Power spectrum incorrectly yielding negative values
I have a real signal in time given by:
And I am simply trying to compute its power spectrum, which is the Fourier transform of the autocorrelation of the signal, and is also a purely real and ...
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Best way to to find fitting parameters for time series of decaying-growing oscillator type
I have discrete time series emerging from the numerical simulations.
It means that the time series can be slightly noisy.
The time series should "obey" to the following formula:
$$ \psi(t) = \sum_{i=1}...
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Amplitude at a given frequency in a wide band signal
Could anyone suggest the most computationally efficient method for finding amplitude at a given frequency having a noisy wide band signal.
To be more specific about a task. I have some physical ...
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334
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Estimating Regions of Flow in Grayscale Video
I am looking to find an algorithm/method by which I can detect regions of flow in a video. The video is that of a grayscale heatmap where the majority of the image is not in motion. The areas that are ...
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Fast Forward Laplace transform
There are examples for fast numerical inversion of the Laplace transforms. For example here:
http://www.mathworks.com/matlabcentral/fileexchange/32824-numerical-inversion-of-laplace-transforms-in-...
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Am I using the incorrect implementation of the fast Chebyshev transform?
I was told that the fast Chebyshev transform has superior spectral convergence, but I am unable to verify its rumored convergence. I was given plots of its spectral convergence, where the signal's ...
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Creating Periodic Noise in Matlab and then adding it to a signal
I am not sure if this is the correct forum for this question but here it goes. If this is not the correct forum please direct me to the appropriate forum.
I wish to add some periodic noise to a 1-D ...
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Parametric spectrum estimation using aryule: difference between Python and Matlab
I have some code illustrating my problem below. As you can see from the results- Matlab is significantly faster than python. It seems that the function which performs the levinson durbin recursion in ...
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385
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How can we compute statistics of the DFT of a random signal?
I would like to know how to compute the statistics of the discrete Fourier transform of a noise signal. To illustrate what I mean, I will first explain in detail a computation I have managed to do ...
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Error in treating non-uniformly spaced data as uniform
In discussing smoothing filters,
Numerical Recipes p. 772 says
... irregularly sampled data, where the values $f_i$ are not uniformly spaced ...
one can simply pretend that the data points are ...
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Calculate large and small frequency separation for the Sun
I want to determine the big and small frequency seperation from timeseries data for the sun. An excerpt of the data (timeseries and power series) is plotted below.
The power series is calculated in ...
user4452
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Use Butterworth and Chebychev filters
I need to calculate frequency response, phase response and apply to signals the Butterworth, Chebychev1 and Chebychev2 band-pass filters.
I'm developing in C++ with Qt, and I'm looking for algorithms ...
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What is the best way to find discontinuities of a black-box function?
It was suggested that this might be a better place for this question than Mathematics Stack Exchange where I asked it before.
Suppose one has a black-box function which can be evaluated anywhere (...
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