# Questions tagged [periodic]

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### finding period with autocorrelation is not correct

I have recorded a signal, which I know is periodic (apart from noise). The period length is unknown. I want to extract the last period from the signal. Before going to a noisy signal, I first tested ...
61 views

### Confused about the period of a discretised time-series

I have managed to confuse myself about the periods of discretised time series. It is all rather embarrassing. This is one period extracted from my continuous signal (radians on y, time on x): To ...
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### Why DFT exact for periodic signals?

I have in my course notes: $$\sum_{k=0}^{N-1}y(k)e^{-j\omega_nk}\approx\sum_{k=-\infty}^{\infty}y(k)e^{-j\omega_nk}$$ Where the $\approx$ for some reason becomes $=$ when $y(k)$ is periodic. Could ...
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### Fourier transform artifacts

My starting point in what follows is a radially symmetric random field. Taking the Fourier transform of this (and plotting it in logarithm to highlight the patterns), I obtain the following image in ...
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### How to Calculate the Period of the Discrete Time Sequence from Taking Its DFT

This is my discrete time periodic signal, the time resolution of the samples is 0.2ms. And it's periodic after each 11 samples. So the fundamental period of the signal is 2ms or the fundamental ...
920 views

### Finding if a signal is periodic

Hello I just started learning Signals and Systems and I have a question regarding periodic signals. For instance: $x(t) = \cos(3.2t) + \sin(1.6t) + e ^{j2.8t}$ is periodic because of the HCF of the ...
220 views

### Testing discrete data for periodicity

I have some data which looks roughly periodic - is there a nice way to measure this? This is an example I'm working on and I'd like a metric that I will be able to just threshold to give a decision ...
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### Determine whether a signal is periodic or not and get fundamental period

Here is my signal Cos(n/2)*cos(pi*n/4) cos(n/2) has period 4pi and cos(pi*n/4) has period 8 Now, the question is will the signal be periodic for fundamental ...
691 views

### how to sample sine wave to 4 points dft output

sinusoid x(t)=1+sin(2*pi *500) sampling rate :1000 samples/s Can I have 4 points DFT output with the above data.
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### Phase reference of a periodic signal

Assume an arbitrary (discrete) signal that is periodic and known over a whole period. I need a way to select a characteristic point along the signal such that I can always retrieve it even when the ...
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### use prony method for damped exponentials

let us consider represented of damping exponential model by prony method,there is source code ...
223 views

### Fourier transform with periodicity at the harmonic frequency

Let's suppose I have a signal $F(t)$ that is periodic, with two periodicities $P1$ and $P2$, with $P1>P2$ Suppose that I know the values of the two periodicities. Using the Fast Fourier transform ...
876 views

### ARMA models for non stationary signals

let us suppose that we have non stationary signal,whose value is given by ...
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### Spectral leakage - understanding the integer number of cycles while windowing

I am reading tutorials about windowing and have read following sentence: For an integer number of cycles, all smoothing windows yield the same peak amplitude reading and have excellent amplitude ...