Questions tagged [sampling]
In signal processing, sampling is the reduction of a continuous-domain signal to a discrete-domain signal.
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Question About Sampling White Noise
Assuming that we have a continuous signal $v(t)$
$$v(t) = \int_0^t g(u)\, \mathrm du\tag1$$
where $g(t)$ is white noise.Then take the derivative of it.
$$\frac{\mathrm d}{\,\mathrm dt} v(t) = g(t)\...
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Getting SNR of reconstructed signal in MATLAB
I am trying to run code to compare the efficiency of various basic sampling methods such as ideal sampling, natural sampling and so on. I want to then use average power to see how accurate the ...
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Determining timing error for sampling
I am writing a small program for sampling a series of sensors on an Arduino. The sampling process is not 100% perfect, depending on how many sensors I am reading, the actual difference between two ...
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4answers
47 views
What's the advantage/disadvantage of oversampling followed by decimation, verses sampling at the correct rate to begin with?
I read somewhere that oversampling somehow reduces sampling noise? How to quantify the reduction in noise? and why would it reduce noise if you are decimating the oversampled signal. What's the ...
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Range of updated/new time axis after upsampling?
I am reading the book "Signals and systems laboratory with MATLAB" by Alex Palamides and I am reading system properties on pg 154 of the book but I am confused about an example shown in attached photo....
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16 views
relation between Nyquist sampling theory and regression
Regression is mainly about estimating a function when only a finite number of samples of the function are available. Theories usually care about asymptotic performance as the number of samples tends ...
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3answers
535 views
Compress a signal by storing signal diff instead of actual samples - is there such a thing?
I am working with EMG signals sampled at 2kHz and 16 bits, and noticed that they "look smooth", that is, the signals are differentiable, and if I apply a "diff" function (...
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What exactly is captured in a Sample of the Nyquist-Theorem variety?
I'm new to DSP and was thinking of sampling in the traditional music creation way, in that you capture a sound and play it back, warp it, etc., but when I thought about the Nyquist theorem, I realized ...
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Intuitively, why is the comb function the sampling function?
The comb function can be used to sample a continuous signal. The comb function is defined as follows
$$
C_T(t) = \sum_{k=-\infty}^{\infty} \delta(t - kT)
$$
where $\delta$ is the Dirac function, ...
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1answer
64 views
Understading sampling theorem and aliasing
A real-valued analog signal with a flat spectrum between f = 0 Hz, and fmax is sampled at a sampling frequency fs = 24 kHz. The sampled signal is then processed with an ideal lowpass filter with ...
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2answers
57 views
Ideal sampling using sinc funcion
Let $ x(t) $ be a bandwidth limited signal such as $ \forall |\omega|>\frac{\pi}{T} : X^F(\omega)=0 $ while $ X^F(\omega)$ is the signal's Fourier Transform.
Let us denote $y[n]=\int_{-\infty}^{\...
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2answers
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What Does 'Zero Order Hold' and 'First Order Hold' Mean?
While studying the Image Magnification in spatial domain, I have come across this definition of Image Magnification by Replication:
Replication is a zero order hold where each pixel along a scan ...
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47 views
Alignment of 2 Set of Samples from Different Sensors
If we measure the heart rate of a subject with two different devices, which have big different sampling rates then how we can compare their outcomes. For instance, one of the devices has the sampling ...
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3answers
254 views
Precise 5th and 7th harmonics of a sampled sine wave
Does anyone know in decibels (to 1/100th of a dB) what the theoretical 3rd, 5th and 7th harmonic of a 0dB fs 24-bit (i.e. full-level; 0dB = -8,388,607 to 8,388,607) sampled sine wave without dither ...
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2answers
57 views
Multiple different length Windows for high resolution realtime FFT
I am looking at trying to achieve a 'realtime' (as quick as possible to acquire, process and present data) FFT application to analyse audio.
I have setup my app to acquire a set of samples, apply a ...
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2answers
52 views
Periodicity of sum of discrete signals
In my lecture slides for school and from this website here
"The sum $z[n] = x[n] + y[n]$ of periodic signals $x[n]$ with fundamental period $N1$, and $y[n]$ with fundamental period $N2$ is periodic ...
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histogram bin size vs. data sampling rate
I have a set of numerical signals that give me a set of zeros calculated based on some numerical procedure. I make a histogram of those zeros.
Here, a following problem arises:
If the histogram ...
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2answers
43 views
How to select the sampling frequency when the input signal frequency is not known
I am trying to observe the noise produced by UPS present in our lab, under no load (a normal running condition when its power is on). As I don't know its frequency range, I have randomly chosen 4 ...
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1answer
58 views
Relationship between the autocorrelations of X(t) and X(nt)
Defining:
$X(t)$ WSS random process with autocorrelation function $R_{X}(\tau) = \mathbb{E}[X(t)X(t+\tau)]$.
$Y[n] = X(nT)$ (sampling of $X$ at a rate $\frac1T$) with autocorrelation function $R_Y(\...
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Looking for a analytical formula to compute the central frequency of a signal analyzed by a discrete wavelet at a given scale
I am reading this paper by Han et al. (2014). In this article, the authors extract detailed information from geomagnetic data sampled at 1Hz using a daubechies 5 (db5) wavelet: they reconstruct the ...
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1answer
30 views
Amplitude Response at greater than half the sampling frequency
I am hoping to clear up some confusion I have. In a lab I am taking, we analyzed the amplitude response of a simple system. We found that as we increased the input signal frequency to greater than ...
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28 views
Minimum sample frequency that allows reconstruction of information signal but VIOLATES Nyquist?
Say in the frequency spectrum, you have an information signal between (-100, 100) Hz, and a noise signal between (-700, -500) and between (500, 700) Hz. What is the minimum possible sample frequency ...
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1answer
46 views
Nyquist frequency , sampling distance
I have few questions I tried to solve regarding nyquist theorem, and I would like to see your opinion if I'm doing it correctly?(one I know the answer second one not sure).
1.Let $f(x)$ and $g(x)$ be ...
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2answers
70 views
Nyquist sampling
I know that if $f_\mathrm{m}$ is the "Nyquist frequency" (max frequency) and $f_\mathrm{s}$ sampling rate then $f_\mathrm{s}>2f_\mathrm{m}$.
Am I correct so far?
I have a signal $x(t)$ with max ...
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0answers
27 views
What is wrong with my PSD computation?
I'm trying to calibrate the RX of my SDR Board to become a measuring receiver. I.e, by connecting it to a known source of power (in my case, a frequency generator), at a fixed frequency, I'm trying to ...
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1answer
88 views
Definition of DSP Terms
can someone define/explain briefly (or with some detail-> up to you) the following terms:
Block Processing? and what are the differences between it and Sample Processing?
(removed)
What is a 3D ...
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1answer
16 views
Sampling Frequency and Spectral Regrowth
Sampling a cosine wave of 10 Hz at Fs = 64 and number of samples Ns = 256
I setup my time vector for the cosine wave as n=(0:Ns-1)*(1/Fs)
If I change the sampling frequency from 64 to 64.0005 I get ...
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0answers
24 views
Why is my resampled signal cutoff when resampling with a windowed FIR filter in MATLAB?
I have an exercise to write a function which upsamples or downsamples a signal by a factor of F (integer) using a FIR filter windowed with a Kaiser window function. Exercise I had last week included ...
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0answers
33 views
How to obtain the steady state response of the sampled periodic signal data?
Below the green plot Vin is 5Hz sine voltage signal from a function generator output sampled at 12kHz sampling rate:
The blue plot Vout is the processed/filtered data by using the following code in ...
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2answers
28 views
Frequency Resolution Problem
Im trying to tackle the following problem while still not having a firm idea on what "frequency resolution" means :
Suppose we sample a continuous time signal with sampling period Ts = 1/2000, and ...
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1answer
47 views
Sample-rate, filtering, digital-filtering and aliasing
I am strugling with a question that I hope someone can help me with.
I am recording single molecule events which I detect is picoampere square deflections.
I wish to use as gentle low-pass bessel ...
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1answer
40 views
Nyquist Rate (Sampling Frequency) for $ {f}^{2} \left( x, y \right) $
We are given that $f(x,y)$ is highest frequency is $\omega$ what will be the frequency sample rate if we want to restore the function of the form $g(x,y)=f^2(x,y)$
Would it be correct to say that ...
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1answer
74 views
Calculate bandwidth of a signal for Nyquist–Shannon sampling theorem
I have to calculate the minimum sampling frequency for the Nyquist–Shannon sampling theorem which is Fc > 2*B, where B is the signal bandwidth.
I have this signals: $\text{sinc}^5(t/2 - 4)$ and $\...
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1answer
24 views
What's wrong with this Whittaker-Shannon-Kotel’nikov interpolation implementation?
I tried to implement Whittaker-Shannon-Kotel’nikov interpolation formula but I get unexpected results: the reconstructed signal lags with respect to the original.
I know that I can not expect a ...
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1answer
38 views
Sampling - Higher order harmonics
I have been studying about the sampling theorem and it seems that even though we sample at a frequency with the nyquist criterion, the harmonics (due to sampling process) remain within the nyquist ...
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1answer
144 views
What is the relationship between angular frequency and normalized angular frequency
This is a slide from my lecture notes:
My professor used the following words " We denote digital frequencies with capital letters and analogue frequencies with lower case letters"
The problem I have ...
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0answers
43 views
Proving Nyquist Sampling theorem for strictly bandlimited signals
I understand that the Nyquist sampling theorem dictates that the minimum sampling frequency, $f_s$, be s.t. $f_s > 2B$, where $ B $, is the bandwidth of the signal. I have read the explanation for ...
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1answer
239 views
Sampling and reconstruction of signal in Matlab
I'm trying to write a program in Matlab that samples (using Nyquist theorem) and recovers signal. I got stucked on recovery part...recovery signal doesn't match with the original one (see photo).
And ...
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1answer
53 views
Fourier like spectral analysis with uneven intervals and redesigned DFT matrix
I intended to use a discrete Fourier transform (DFT) on a time series sampled at uneven intervals. What I did was to calculate a DFT matrix where the elements are the values at the uneven locations ...
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1answer
36 views
What does the frequency band mean when it comes to finding aliases?
The time signal which i'm trying to find the aliases for is:
$$x:{\mathbb R}\rightarrow {\mathbb R}\\\ x(t)=\cos(50t) +2\cos(70t).$$
If the sample period is $T_s = \frac{\pi}{60}$ then according ...
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1answer
38 views
amplitude of upsampled and downsampled signal without filter
Given:
$$
DTFT\{x[n]\}=X(\omega)= \begin{cases}
1 & |\omega| \leq 2/\pi
\\
0 & 2/ \pi < |\omega| < \pi
\end{cases}\ \ \ \ \ (periodic\ 2\pi)
$$
If I downsample $X(\omega)$ by M. I get:
...
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1answer
26 views
Frequency spectra of a sampled process
I have a process $X$ with frequency spectra
I sample this process with sampling frequency $f_s = 2$.
What will the frequency spectra $R_z(f)$ of the sampled process $Z$ look like? I realize that ...
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1answer
35 views
Isosurfaces from three dimensional column data: methods
I have just been asked the following question, and I somehow felt short of smart answers. You are given a series of $N$ triplets of values ($P_1$, $P_2$, $P_3$), pertaining to physical measurements. ...
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1answer
74 views
What is Finite Rate of Innovation Signal?
I have read about Finite Rate of Innovation signal by Martin Vetterli in here. But i do not understand several basic things
The paper said that finite rate of innovation is the number of degree of ...
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29 views
How to simulate measured data with antialiasing filter
I wish to simulate measured data for developing signal processing methods. All properly measured data will have been through an antialiasing filter. How do I generate such simulated data? I have ...
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1answer
64 views
Choosing a Sampling Rate and a Cutoff frequency
I have an assignment:
You wish to generate a pure 1000 Hz tone digitally using a computer. How would you choose a sample rate that assures that you could generate the tone and use the same sample ...
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1answer
36 views
upsampling for a signal
We have a signal $s(t)$.
If we do an upsampling, does the signal duration increase?
What is the point of upsampling if the signal time increases?
Can we do an upsampling if we don't use a shaping ...
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1answer
64 views
Follow up question regarding: “Complex sampling can break Nyquist?”
I'm having some trouble understanding the sample rate limitations when considering a complex baseband signal.
I understand (based on the linked SE questions below), the either (1) physically ...
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1answer
419 views
Passband vs Baseband Bandwidth
Bandwidth is the difference between the upper and lower frequencies in
a continuous band of frequencies. A key characteristic of bandwidth is
that any band of a given width can carry the same ...
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1answer
56 views
Signals sampling
I have a simple question, but sadly I'm kind of "noob" in signals theory.
A signal having 4 harmonics at the following frequencies: 1 kHz, 2 kHz, 3.5kHz and 4.2 kHz.
(How can a signal have harmonics "...
