Questions tagged [periodic]
The periodic tag has no usage guidance.
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0answers
36 views
How to find the period of a given signal? [duplicate]
I'm new to Signal Analysis. I have a manually generated Signal from a Gyroscope, which looks like in the picture below and I need to extract the X-Values for each period. Is there some technique to ...
1
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1answer
58 views
Why does this not work: Alt. way to compute the period of a discrete periodic signal that is a sum of 2 complex exponentials
I want to compute the fundamental period of the following discrete time signal:
$ x[n]= \exp^{(j\frac{2\pi}{3})n} + \exp^{(j\frac{3\pi}{4})n}$
I know I can do this by taking the fundamental periods ...
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0answers
17 views
How to find the filter coefficient of matched filter to detect the pulse of a signal?
I would to understand how to find the coefficient of a matched filter.
Let's consider we have a signal and the signal is buried in the following noise. we want to find the coefficient of a matched ...
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0answers
33 views
Periodicity of $\cos(2n + \theta)$
I have to calculate periodicity of e^j(2n + π/4)
If cos2n is Aperiodic then what is the periodicity of ...
1
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1answer
34 views
What is a periodic signal in image processing?
In the context of image processing (and computer vision), the concept of convolution comes up a lot. Convolution is quite related to the concept of Fourier transform and DFT. In the context of image ...
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2answers
108 views
Fourier Transform of Alternating Periodic Rectangular Pulse
I'm having trouble determining Fourier transform of signal. I have 2 ideas on how to solve this problem.
Given the signal is periodic I could use formula for Fourier transform of periodic signals:
$$...
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1answer
49 views
Finding period of a square wave with varying sampling frequency
I have a square wave (0-1.8V) with a varying sampling frequency (from a circuit simulator). It is also not a perfect square wave (the high and low signal could be very close to but not precisely zero ...
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2answers
56 views
Finding periodicity in discrete events
I have a program that detects events in a large amount of measurement data. When it detects an event, it writes a timestamp. I have thousands of event timestamps. What I wish to do is detect if there ...
2
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2answers
51 views
Making sense of the periodogram
I am trying to use the periodogram to tell when a signal is periodic or not by following the tutorial for the astropy Lomb-scargle periodogram here.
http://docs.astropy.org/en/stable/stats/...
0
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1answer
36 views
Reason of effect of continuity and discreteness on periodicity of signal?
We know that a sine signal in continuous time is a periodic signal with a period $2\pi$ whereas the same sine signal in discrete time is aperiodic.
My question is how changing just a type of signal (...
1
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1answer
197 views
How can I improve my fit of cosines to periodic data using Python?
I have a space-separated csv file containing a measurement. First column is the time of measurement, second column is the corresponding measured value, third column ...
0
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1answer
44 views
periodicity of constant discrete time signals
are constant discrete time signals periodic?
example \begin{equation}
e^{i10\pi n}
\end{equation}
my proffesor says that this signal is aperiodic, in the discrete sense. but it seems wrong, because
...
0
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1answer
74 views
Does dividing the magnitude spectrum of white noise by sqrt(2) give an RMS magnitude spectrum?
I understand that the RMS Amplitude of a sinusoidal signal is around 0.707 ($\frac1{\sqrt2}$) times the Peak Value, but this is not true for noise.
However, an FFT of a noise signal indicates ...
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2answers
53 views
Discrete signal testing for periodicity
How would one go about determining if the following discrete time signal x[n] is periodic, and if it is, determine its fundamental period?
I understand that the ...
0
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1answer
41 views
Finding the fundamental period by using four elementary operations (+,-,x,/)
The idea is to find the fundamental period of any periodic and bounded signal. This is all that we know about the signal. Nothing else. Only allowed operations are: $+,-,\times , \div$. We can also ...
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3answers
57 views
Ideal sampling of audio signals-Periodic spectrum [duplicate]
When applying ideal sampling on audio singals, why is the spectrum periodic ?
2
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3answers
81 views
Why must the angle contain $\pi$ for $\cos$ be periodic?
The $\cos(\frac{n}{6})$ is aperiodic, and $\cos(\frac{n\pi}{6})$ is periodic, why? What role does the $\pi$ play? By the way, $n$ must be integer
I have seen this question,Why is cos(n/6) aperiodic? ...
2
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2answers
2k views
How do I find the fundamental period of the given signal?
I am having a problem in finding the fundamental period of the signal $x(t)$ given below:
\begin{align}
x(t) &= 2\cos\left(\frac 45 \pi t\right)\sin^2\left(\frac{16}{3} t\right)\\
&= 2\cos\...
1
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1answer
39 views
how to extract a period of a periodic pulsed signal?
I rercorded a sequence of zeros and ones which is repeated many times. However, the first and the last repetitions may not be complete because I have to start recording at a random time, so the ...
0
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1answer
95 views
Estimating variance in arbitrary, periodic signal
I have a periodic signal $x[m], m \in [0;M-N+1]$ made of modulated templates $s[n],~ n \in [0;N-1],~ N \ll M = NK$ of finite energy and support (i.e. zero outside of its defined interval, which does ...
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1answer
23 views
detection of periodicities in n-dimensional signals
Generally speaking, what analyses are necessary and sufficient for the detection of periodicities in an n-dimensional signal amounting to a discretely sampled density distribution over n-dimensional ...
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1answer
91 views
Remove multiplied white noise from periodic signal
I need to remove noise that is multiplied to a periodic signal using a maximum of 7 periods having no information about the noise.
I have tried to use auto-correlation:
...
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0answers
93 views
State Space conversion of Sinusoidal model
i would like to learn how to convert sinusoidal model into state space form which has following equation
our model consist of sum of periodic components with additive of white noise, given by ...
0
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1answer
36 views
Numerical error while implementing a periodic pulse signal
I'm trying to illustrate the principle of constructing a periodic signal using an elementary pattern. This is the code I use (python 2.7 + numpy + scipy.signal) :
...
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1answer
66 views
Is Oversampling a Signal Same as Discretizing the Signal?
I am confused about the new terminology 'oversampling' I have encountered very recently.
To explain it better, I am going to use numerical examples.
Now let's assume I am using a BPSK modulator and my ...
0
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2answers
848 views
Calculating the complex signal's average power
$$x(t) = \cos(\pi i t/20+\pi/4) - 2je^{j \,12\pi i t} + 5\sin(2\pi i t/3+\pi/3) $$
I need to find the signal's average power.
How can I do that?
The $i$ index (represented in red in the below image) ...
2
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1answer
308 views
Fourier coefficients of product of two periodic signals
question:
If $x(t)$ and $y(t)$ are two periodic signals(both with period T) with Fourier coefficients $c_{n}$ and $d_{n}$ respectively then, Fourier coefficient of $z(t)=x(t)\cdot y(t)$ is:
(a) $\...
2
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4answers
184 views
Very basic question about how we define frequency in signal processing
When talking about general periodic continuous-time signals for which $$x(t + T_0) = x(t)$$ where $T_0$ is the fundamental period we define the fundamental frequency $\omega_0$ as $\omega_0 = 2\pi/T_0$...
3
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2answers
2k views
Finding the fundamental frequency of a periodic signal
Suppose we have the signal $$x(t) = e^{j\omega_1 t} + e^{j\omega_2 t} + e^{j\omega_3 t},$$ where all the frequencies are rationally related (that is, the ratio of any pair of frequencies is a rational ...
2
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1answer
49 views
Rationally related frequencies and the Fourier Series representation
Suppose that we have the signal $$x(t) = e^{j\omega t} + e^{j\frac{3}{2} \omega t},$$ and we want to find a Fourier Series representation for that signal. Is this possible? According to my ...
-1
votes
1answer
419 views
sum of two periodic signals with different length
So, I have those two signals (x1,x2) and I want to make a new signal (x) which is the sum of them. What bothers me here is the length of each one of the signals. I made this little code over here in ...
1
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1answer
374 views
DFT shift theorem proof
Learning DSP on my own time. Can't figure out the proof for DFT shift theorem which states the following:
Given, $x[n]$ to be a periodic with period $N$, $\text{DFT}\{x[n]\} = X[k]$, then
$$
DFT\{x[n-...
1
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2answers
176 views
Fourier Series of Aperiodic convolution of periodic functions
we were given the following classic exercise:
Given two periodic signals $x(t), y(t)$ with fundamental period $T$
with Fourier series coefficients $c_m^x, c_m^y$ respectively, find the
Fourier ...
3
votes
3answers
238 views
formula derivation for periodic signal power
Studying DSP on my own. Taking an introductory class. Was given a formula for signal power
$$ P = \lim_{M\to\infty} {\frac{1}{2M+1} \sum_{n=-M}^M} \lvert x[n] \rvert^2 $$
I do understand why the ...
2
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1answer
62 views
Periodic signal checking when using $\Sigma$
Is the following signal periodic?
$$ \sum_{κ=-\infty}^{\infty}\left[\mathrm{rect}\left(\frac{t+2κ}{10}\right)\right]+\cos\left(\frac{π}{75}t\right) $$
where rect is the rectangular signal
-3
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4answers
85 views
Signal periodicity in discrete-time
Let $x[n]$ be a discrete-time signal, and let
$$y_1[n]=x[2n]$$
You have to show that if:
$x[n]$ is periodic, then $y_1[n]$ is periodic. $y_1[n]$ is periodic,
then x[n] is periodic.
So for the ...
0
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1answer
185 views
Phantom harmonics when using cosine windows why do they appear and how to avoid them?
Given an L order cosine window, it is possible to show that the width of the main lobe is given by:
$$\omega_w = \frac{2 \pi L}{(2N+1)}$$
Where $L$ is the order of the window, $N$ is the maximum ...
3
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3answers
1k views
Periodicity of a constant signal!
This can be a very silly question, but I'm quite confused:
If we take the Fourier transform of any constant signal, we get an impulse at zero, which says that its frequency is zero and, hence, it is ...
0
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1answer
69 views
What is special about the frequency $\omega_0=\pi$ that suddenly causes rate of oscillation decrease?
In Alan Oppenheim's book Signals and Systems a comparison is made between the properties of discrete-time and continuous-time complex exponential signals in section 1.3 pg. 26. Specifically it says:
...
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1answer
120 views
Confusion about subtle difference between discrete-time and continuous-time
In Alan Oppenheim's book Signals and Systems a comparison is made between the properties of discrete-time and continuous-time complex exponential signals in section 1.3 pg. 26. Specifically it says:
...
3
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2answers
106 views
periodicity coefficient
I wonder if an efficient method exist to compute how much a signal is periodic, it should be ~1.0 when the signal is totally periodic (like a sinusoïdal signal) and ~0.0 when totally random, like a ...
4
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1answer
230 views
Fourier Series Coefficients
Question:
The fourier series coefficients is given as:
$$c_k= \begin{cases}
1 \qquad & k \ \text{ even} \\
2 \qquad & k \ \text{ odd} \\
\end{cases}$$
the period of the signal is $T=4$, ...
0
votes
1answer
573 views
How to calculate the FFT period
I have a question about finding the FFT duration for 802.11a preamble.
According to the standards, when the bandwith is $20 \textrm{MHz}$ and for $N=64$ we have $\Delta f = 20\textrm{MHz}/64 =312.5 \...
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0answers
48 views
Determining periodic pattern when there is pattern which period is multiple of former
I have periodic signal, say, it has year period, yearly pattern. I want to check if also has quarterly pattern.
Event if there is no visible quarterly pattern, Fourier Transform of this signal has ...
2
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2answers
165 views
Detecting pattern from signal data by gaussian mixture model?
I'm a machine learning newbie.
I have sensor data which is generated by several sensors.
The data is a series of 'time's. (it is not labeled, in other words, I cannot know which sensor generates ...
0
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1answer
146 views
Is sum of period samples in the DSP domain?
Following program outputs sum of samples of signal's period. Values in program are:
...
0
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1answer
2k views
How to find the period of a noisy signal using MATLAB's $\tt xcorr$?
Here is my code:
function [ T ] = FindPeriodicity2(x,Fs)
ac=xcorr(x,x);
[~,locs]=findpeaks(ac);
T=mean(diff(locs)/Fs);
end
and when I pass the signal ...
1
vote
1answer
473 views
Looking for cycles of periods longer than the input signal length
There was a similar question asked here, however I would like to focus on some specifics of this problem. Let me present the Python code sample to illustrate the situation when only a part of the ...
3
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1answer
326 views
Determination of periodicity in data and finding mean
I have to find whether there is any pattern (I mean periodicity or close to periodicity) and if there is, for one cycle i have to perform numerical integration to determine mean. In the first picture ...
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1answer
159 views
Periodicity of signals
$$x(t) = \cos(2 \pi t) \cdot u(t)$$
$$y(t) = x(t) + x(-t)$$Is $y(t)$ periodic. If so, what is the $T$?
$$x(t) = \sin(2 \pi t) \cdot u(t)$$
$$y(t)= x(t) + x(-t)$$
Is $y(t)$ periodic?
