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Questions tagged [nonuniform]

Nonuniform sampling means that the spacing between samples are not equal quantities of time or some other physical variable. Normally the sampling instances (and therefore spacing) are known, but the intervals between adjacent samples are not constant.

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Periodic non-uniform sampling - effective bandwidth to select correct anti-aliasing filter

What is the effective bandwidth of sampling at a rate $f_s$ for a burst of $N$ samples, where the bursts are triggered at rate $f_B$? For example, say $f_s \approx$ 10 kHz, $N \approx$ 1000 and $f_B \...
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For non-uniformly sampled data, how to decide whether interpolation or Lomb-Scargle periodogram is better?

When handling non-uniformly sampled data, we can use one of the following methods to estimate the frequency spectrum: Interpolation in time/space domain, then go for classical periodogram OR Use Lomb-...
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Recovering signal statistics from non-uniform sampled signal

I'm interested in estimating the mean and standard deviation of a signal that was sampled non-uniformly. Assuming I have an estimate of the signal bandwidth, what algorithms would provide estimates of ...
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218 views

Reconstruction of a signal from non-uniform samples [duplicate]

So I'm having some troubles with a signal that's been sampled but where the samples don't have consistent intervals. I've been looking into the NFFT (in python) as a starting point but I'm a complete ...
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96 views

Spatial spectrum of EEG data: non-uniform DFT?

I want to compute the spatial spectrum of EEG data collected using a non-uniformly sampled grid of sensors (as in the figure below). One way to do this would be to interpolate the data on a ...
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60 views

Non-uniform resampling - spacing between output samples given speed factors

I'm working on an implementation of time-varying resampling in python. I've got the windowed sinc interpolation itself working nicely, but can't figure out where exactly to sample my input data for ...
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108 views

Which type of quantization is better?

If a signal's amplitude has a uniform PDF, which is better in the sense of producing a smaller quantization error: optimal scalar quantization or quantization with compressor (non-uniform quantization)...
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140 views

How to calculate spectrogram from nonstationary, nonuniformly sampled signal

I have a high resolution 3D spatial signal (xy-elevation data collected via Terrestrial Laser Scan) with very nonuniform sampling (holes/shadows due to vegetation; point spread varies as a function of ...
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155 views

Denoising short, non-uniformly spaced, bandlmited sequences

Consider a bandlimited signal $x(t)$ with bandwidth $BW$. Samples of this signal are observed at non-uniformly spaced sample points in the presence of noise: $y(t_i)=x(t_i) + n_i \qquad i\in\{0,1,\...
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113 views

Non-uniform acquisition to fixed sample rate

I'm facing a challenge that requires me to process a signal from an engine knocking sensor. The acquisition is done synchronously with the engine speed (every 0.1 degree) which gives me a range from ...
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2k views

Resampling of signal with non uniform sampling frequency

I have a non uniform sampling frequency signal and I have to convert it in a constant sampling frequency. I tried to interpolate it with an Hermite spline interpolation but it make a lot of wrong ...
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1answer
305 views

2d dft of a scattered signal

I want to take the DFT of the data shown in the image. Note: my data consists of $(x,y,z)$ values for which I have shown $(x,y)$ in the image (i.e. their location). '$z$' is the amplitude of the data ...
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Methods for edge detection with non-equidistant samples

This posting describes two methods of edge detection for wave analysis in a water pipe. I am not sure about advantaged and disadvantages. Therefore I want to evaluate the best method for this ...
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148 views

non-equispaced DFT bandwidth

I need to construct Fourier transform of non-equispaced data. That is, I have signal $s(t)$, $t\in[0,T]$ sampled at non-equispaced points $t_k$, $k=0...N-1$ with sample values $s_k = s(t_k)$. For ...
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2answers
307 views

Nonuniform sampling band-limited gaussian white noise

I'd like to sample band-limited Gaussian white noise non-uniformly. One way to approximate this would be to filter Gaussian white noise with a lower cutoff frequency and non-uniformly pick samples ...
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1answer
283 views

Mathematical model of equivalent-time sampling, the resulting unevenly spaced periodic signal, and its interpretation

I sample a continuous signal $s(T)$ over time. This leads to $s[t]$, which depends on several factors of which some are (pseudo-) periodic. I am interested in the effect of one such periodic factors ...
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75 views

Period of non-harmonic Fourier sum

I am wondering if there is a formula for the period of the sum of $N$ cisoids of the form $e^{j\frac{2\pi}{N} i\, \omega_k}$ where the frequencies $\omega_k \in \left[-N/2,N/2\right]$, $k=0,\ldots,N-1$...
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389 views

Non Uniform DFT Algorithm by Dutt & Rokhlin

I have implemented Dutt & Rokhlin's FFT algorithm [1] for non-equispaced data but for some reason I am getting very large errors ($E_2=0.04$ and $E_\infty=0.1$). I was wondering if there are any ...
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1answer
153 views

What is the optimal adaptive grid for calculating a DFT using a fixed number of sampling points?

I'm currently facing the following problem: I want to approximate the Fourier transform $F(\omega)$ of a (let's say, $L^2(\mathbb R)$) function $f(x)$ by calculating the discrete Fourier transform, ...