Questions tagged [sampling]
In signal processing, sampling is the reduction of a continuous-domain signal to a discrete-domain signal.
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questions
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DFT for signals of different length and sampling rate
I would like to compare oscillations of biological object. I have multiple datasets which are taken with different sampling rate and have different length.
My current workflow:
Take derivative, ...
0
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4answers
47 views
Why is In-phase Quadrature sampling not used to record and store digital audio?
I/Q is a standard method to sample radio frequency and its use is even seen in some non radio signals like sonar. But it seems that it is not used to sample acoustic frequencies.
What property of ...
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1answer
54 views
Fourier Transform of sampled reflectance measurements
Goal:
Calculate the complex index of refraction ($\hat n = n +jk)$ from reflectance measurements.
Data:
Reflectance measurements for various materials were taken with a FTIR (Nicolet™ iS50 FTIR, ...
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0answers
15 views
Sampling points on a face of a human body mesh
Is there a known shape analysis technique to sample points of a not necessarily naked human body mesh (more specifically the head part).
The goal would be to randomly sample (uniform distribution) ...
0
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2answers
67 views
How do Anti-Aliasing Filters filter the signal?
I have programmed a anti-aliasing filter that uses the fourier-transformation and makes a perfect cutoff on my desired cutoff frequency for downsampling without aliasing.
I have read about other ...
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0answers
30 views
Canceling interference (such as harmonics from out of band source )
I have a vague-ish question, if it makes sense:
The desired received signal (from source S1) was carried at 3 GHz passband carrier frequency, with bandwidth 20 MHz. It was interfered with by the 3rd ...
0
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3answers
37 views
does aliasing occur always if i sample a vibration in real world applications?
I was reading about the aliasing effect and nyquist. I understand that aliasing effect occurs if the sampling rate is lower than twice the maximum frequency in the signal I want to sample.
So I was ...
0
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1answer
45 views
Nyquist theorem vs sampling theorem vs shannon sampling theorem?
Is there any difference between these three?or these are just three names of same theorem?
0
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1answer
37 views
Phase difference measurement of a 100 kHz tone
I would like to measure the phase difference of a 100 kHz tone. The tone is transmitted and then received.
The received tone is sampled using an 1 MHz 12 bit ADC(IQ) and the SNR is at least 35 dB.
...
0
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2answers
38 views
Interpretation of sample rate
I'm a little confused about the sample rate:
If I have an audio file that was recorded with a sample rate of 48kHz, this means that there are 48,000 values per second in this file, right?
So when I ...
4
votes
5answers
187 views
Reconstructing/interpolating small regions of a bandlimited signal by taking the fewest possible samples
I have a signal which is bandlimited and can be sampled at arbitrary continuous positions. The value at any position is given by an expensive computation. I need to do some further computation on ...
0
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1answer
21 views
Doubt in Frequency Modulation code
While searching for something FM, I came across this code. I am not able to understand a particular line of code. I have written a comment against that line of code.
...
0
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1answer
55 views
IQ Sampling and Oversampling Differences? *Confused*
Two different thought process that produce two different alias band calculations .... What concepts are these?
If I have two 1 GHz ADC's and they sample with 90 degree offset (A comment said this is ...
0
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1answer
63 views
How to make low pass filter using frequency sampling method?
https://www.allaboutcircuits.com/technical-articles/design-of-fir-filters-using-frequency-sampling-method/
So there is two main equation:
I wish to filter out frequency $\le 10000Hz$, for example. ...
0
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1answer
46 views
0
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0answers
25 views
removing noise using Scipy.signal.butter:
I am going to remove the noise from a brain recorded signal. It was a continuous recording and with sample rate=30kHz, it was digitized. So now it is a digital signal.
I have written the code here ...
0
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1answer
48 views
Trouble with understanding moving average filter as an oversampling filter
I am struggling with understanding how an moving average filter can increase ENOB in a given sample.
I wrote a test for a simple MA (moving average) filter in matlab. The algorithm to create new MA ...
0
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1answer
59 views
sampling a continuous time signal using MATLAB?
I have a continuous time signal $x(t)=cos(2 πft)$ where $0\leq t \leq 2$.
I want to plot discrete time signal $x(n)$ where $0 \leq n \leq 19$ for sampling frequency 100 Hz and signal frequency 10 Hz.
...
0
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1answer
45 views
Torque signal fft
I have the following torque signal picked up with a 10.240Hz sampling rate from a testbench.
I am studying its fft which I create on Octave with the following code:
...
0
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2answers
64 views
Why is the digital frequency highest at $\pi$ and what does it mean in terms of analog frequency? [duplicate]
I can't seem to comprehend why the digital frequency is highest at $\pi$. I know the relationship between the digital and analog frequency is given by:
$$\omega = 2\pi\frac{F}{F_s}=2\pi f$$
Where $F$ ...
0
votes
1answer
39 views
Build an inverse model for a train of gaussian pulses
I have a stationary signal from a train of Gaussian pulses.
My sampling window is too wide (cannot be reduced). In the example 1 ms. So it is not possible to clearly distinguish one pulse from another....
1
vote
1answer
66 views
relation between DFT to CTFT
The signal $$x(t)\;\;\;\;0\leq t\leq 0.2s $$
We know that the CTFT of $x(t)=0$ when $|w|>2*\pi*10^4$
We sample $x(t)$ in sample space of $$T=25\mu s$$ or $$F_s=1/T=40000Hz$$and we get a series ...
0
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2answers
49 views
find the maximum of the DFT of sampled signal
The signal $$x(t)=\cos(10\pi t+\phi)+\cos(20\pi t)$$ is sampled with a sampling frequency $F_s$ as $25 \mathrm{Hz}$ where the phase $\phi$ is unknown.
Sampling the continuous time signal $$y[n]=x(nT)$...
1
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3answers
71 views
Poisson summation formula and periodic summation of Fourier transforms
One of the forms of the Poisson summation formula is
$$
\sum_{n=-\infty}^{\infty} T\cdot x(nT)\ e^{-i 2\pi f T n}\;
{=} \;
\sum_{k=-\infty}^{\infty} X\left(f - k/T\right),$$
where $x(nT)$ are ...
1
vote
1answer
62 views
Discrete time aperiodic signal: Concept of frequency?
Is concept of frequency to a-periodic signal whether it is continuous or discrete time is valid?
I am bit confused, since discrete time sinusoids have frequency $-\pi<\omega<\pi$ or $-\frac{1}{...
0
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1answer
43 views
Choosing right cut-off frequency for a LP filter in upsampler
I'm implementing a upsample function in Matlab but it's not perfect right now,for reasons I'm not sure. Here is my code:
...
1
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2answers
43 views
How sampling aperiodic signal will result in periodic repetitions of the same
I am reading "Digital Signal Processing" - Proakis and often read that sampling guarantees periodicity (not exact as read)
But I wonder how sampling aperiodic signal will result in periodic ...
4
votes
1answer
46 views
Can the Nyquist sample rate be extended to stochastic sampling?
It appears there are lots of questions here about Nyquist, and a few questions about stochastic sampling here. But I haven't found any that address quite what I'm after. This is the closest I've ...
3
votes
5answers
1k views
A question about sampling rate of cosine signal
Given $$c(t) = \cos(2\pi\cdot 30 \cdot t) $$
If we sample this signal at the Nyquist rate 60 Hz and at a higher rate of 80 Hz, we get the following:
There is no aliasing as $f$ = 30 Hz is less than ...
1
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0answers
19 views
Calculate sampling lattice matrix in 2D
The pattern in which the sample points are distributed in 2 dims, is called a
sampling lattice, and can be defined by a generator matrix.. In 2 dimensions, the generator matrix consists of 2 vectors. ...
1
vote
1answer
90 views
How do I convert a sampled complex signal to a real signal?
I’m writing a Soapy SDR plugin for the FL2K-SDR. Soapy SDR expects plugins to produce and consume IQ samples. However, the FL2K-SDR driver consumes only real samples. I know you can convert a real ...
0
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1answer
32 views
Recoverable continuous function after average sampling
I have a personal interest in this question, but I don't know if it is unfounded.
Suppose I have a continuous function x (t), which is sampled using an average sliding window, which performs a ...
0
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3answers
81 views
confusion sampling vs quantization?
while converting analog signal to digital equivalent,we have a process that is called analog to digital conversion and it has two main steps/stages sampling and quantization? I am confused whether y ...
2
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2answers
251 views
Phase difference between signals sampled at different frequencies
I want to know that if it is possible to measure the relative phase difference between a signal that has been sampled at two different locations with different sampling frequencies? Also can that ...
0
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0answers
13 views
What is the difference between SFO (sampling frequency offset) and SCO (Sampling clock offset)?
What is the difference between SFO (sampling frequency offset) and SCO (Sampling clock offset)?
I think they are essentially the same phenomenon?
1
vote
2answers
85 views
anti-alias filter of square pulses
I'm trying to determine whether or not an anti-alias filter is needed for sampling square waves. The goal is to sample square wave pulses from a video detector with an ADC, do some time-domain digital ...
0
votes
2answers
63 views
Nyquist sampling in image acquisition
I know that in the image acquisition stage, after obtaining the analog image from the sensors, it is sampled and quantized. How the Nyquist sampling is achieved? The sampling frequency must be at ...
0
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2answers
50 views
Sampling $x(t)=\cos(4\pi t)+\cos(2\pi t)$
Imagine that we sample the signal $x(t)=\cos(4\pi t)+\cos(2\pi t)$ with a certain sample frequency $f_s$ and we obtain $x[n]$. Now, by ideal interpolation, we get $y(t)$ from $x[n]$.
How can we know ...
0
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1answer
54 views
ADC sampling rate implications Matlab/Simulink M-PSK modulation
I am trying to find a way to evaluate what would be the minimum sampling rate used in a modulated waveform using matlab / Simulink.
The real scenario would be let say a M-PSK waveform of Y bandwidth ...
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0answers
34 views
How to generate Digital Sine Wave? [closed]
I am trying to generate a sine wave digitally. I am using LMS7200m RF chip from Lime microsystems. I want to generate a sine wave of 100KHz. The DAC on the chip has a sampling rate of 640 MHz with ...
0
votes
1answer
48 views
I/Q plane plot understanding?
I am experimenting with some signals. I ma generating a 2.47 Ghz signal from signal generator and receiving it by an SDR (LMS7002m Rf chip) with Rx frequency tuned to 2.47 GHz. Upon plotting the ...
0
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1answer
69 views
How to determine sampling frequency for an x(t) signal avoiding aliasing?
The antitransform of the function is given:
$ \hat{x}(f) = \frac{123 + i246\pi f}{246 - 24600 \pi^2 f^2 + i4920\pi f} $
I'm asked to determine which frequency can I sample using the function x(t) ...
2
votes
0answers
92 views
Lagrange Vs Sinc interpolation
I was wondering what is the practical difference between Lagrange Interpolation using Farrow Structure and Sinc Interpolation? Both require pre-computation of time offset coefficients using a lookup ...
0
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0answers
36 views
Nyquist sampling theorem / Nyquist - Shannon theorem evaluation over M-PSK
I am trying to simulate an M-PSK Tx-Rx System on Simulink and analyse what the effect of sampling rate reduction would have on it. More, particular I am trying to prove what Nyquist sampling theorem ...
0
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1answer
40 views
How to get RMS to Frequency chart for discrete samples of acceleration?
I’m reading a book on Motorcycle dynamics and want to compare the vibration profile of my motorbike against this chart:
I am not sure how to get the RMS of acceleration at different frequencies.
I ...
0
votes
1answer
68 views
Why is my filter unstable and self-oscillating in this case?
I am using resonant bandpasses to simulate modes of guitar/piano strings for audio synthesis. While attempting to introduce coupling effects I have encountered a problem.
I will illustrate with some ...
2
votes
1answer
71 views
Variance of a signal
How to calculate the variance of noise samples modeled as follows:
$n_a(t)$ is a
Gaussian zero-mean white noise process with (two-sided) power spectral density $\frac{N_0}{2}$. $n_a(t)$ is passed ...
4
votes
3answers
118 views
Digital to analog aliasing or mirror query… DAC can output negative frequency?
Using a clock Fs = 1 MHz.
The Digital to Analog (DAC) can make frequencies upto 500 KHz.
500 kHz to 1 MHz is an alias? Or is it called a mirror?? Is aliasing a concept only on the ADC and sampling ...
0
votes
2answers
72 views
how a signal for which calculate RMS can be filtered and have a fast settling time?
i designed a sinusoidal pwm amplifier (3KHz to 20KHz) that regulates its output voltage reading the RMS value of output current.
The RMS is obtained squaring the signal sampled by AD converter @...
0
votes
1answer
50 views
What is the difference between t=n*Ts sampling vs impulse train sampling?
I know that if I sampling with impulse train so I get in the frequency plane
X(f)*h(f)
(when x(f) is my signal, * means convolution and h(f) is fourier transform of impulse train).
what the ...
