Questions tagged [signal-processing]

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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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1 vote
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118 views

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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3 votes
1 answer
91 views

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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2 answers
86 views

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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1 answer
173 views

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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1 vote
1 answer
121 views

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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2 votes
0 answers
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Normalising DFTs Correctly

I have been playing around with convolutions in scipy's signal package: ...
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1 vote
0 answers
58 views

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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50 views

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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1 answer
65 views

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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2 answers
219 views

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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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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1 answer
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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 ...
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0 answers
52 views

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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2 answers
104 views

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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1 answer
129 views

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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1 answer
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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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1 vote
1 answer
403 views

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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2 votes
3 answers
222 views

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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3 votes
1 answer
331 views

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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2 votes
0 answers
813 views

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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261 views

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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1 vote
1 answer
2k views

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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2 votes
2 answers
1k views

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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4 votes
1 answer
286 views

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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2 votes
0 answers
62 views

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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6 votes
1 answer
437 views

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 ...
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5 votes
1 answer
131 views

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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20 votes
4 answers
5k views

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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