# 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.

19 questions
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1answer
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### 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 ...
2answers
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 ...
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 ...
0answers
57 views

### 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 ...
1answer
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 ...
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 ...
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 ...
0answers
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 $\omega_k \in \left[-N/2,N/2\right]$, $k=0,\ldots,N-1$...
3answers
389 views

### Non Uniform DFT Algorithm by Dutt & Rokhlin

I have implemented Dutt & Rokhlin's FFT algorithm  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 ...
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, ...