Questions tagged [sampling]
In signal processing, sampling is the reduction of a continuous-domain signal to a discrete-domain signal.
739
questions
3
votes
1answer
281 views
Noise PSD and sampling rate relation
Let's consider generating samples of a random process like white Gaussian noise (AWGN). Let's assume I am generating $N$ samples of AWGN with variance $\sigma ^2$ in MATLAB by using randn() funtion i....
1
vote
2answers
596 views
Nyquist frequency and DC
Im studying the DSP book by Steven W. Smith. On page 41 he covers the Nyquist frequency. He makes up an example by writing the following.
... consider an analog signal composed of frequencies ...
1
vote
1answer
149 views
about sampling frequency
I am trying to make a DFT on a signal with frequency f=50 MHz main component plus some noise.
As far as I know if I sample it at F=100MHz I should be able to get a proper plot of the DFT since F=2f ...
0
votes
1answer
63 views
Reconstruction of sampled band-pass signal
I am pretty new to signal processing. I am currently trying to reconstruct a sampled band-pass signal created with the filtfilt and ...
3
votes
3answers
63 views
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
votes
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
votes
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 ...
2
votes
0answers
64 views
How can I extract the 2 polyphase components of a signal after sampling at the half of sampling rate
Suppose I have a continuous signal $x(t)$, which was sampled using sampling function $s(t)$ whose sampling rate is $T_s$.How can I sample the continuous signal by Ts/2 instead of Ts in order to get ...
0
votes
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 (Nicoletā¢ iS50 FTIR, ...
0
votes
2answers
64 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 ...
0
votes
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
votes
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
votes
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
votes
1answer
79 views
Sampling period
I started it but didn't how to continue , any help ?
1
vote
3answers
149 views
How Is a Signal Changed After Sampling?
I can't understand sampling signal mathematically.
for example $x(t) = 2\cos(100\pi t) + \cos(300\pi t)$ and I know I should use sampling frequency $300\textrm{Hz}$ to sample this signal.
and after ...
2
votes
1answer
82 views
FFT of white noise with different sampling rate
I have a question on how I should interpret the white noise power level (noise floor) obtain from FFT for different hardware sampling rates. I realized if I sample the same noise at different rates (...
0
votes
1answer
29 views
Perform frequency analysis on grouped pulses
I have a system which consists of individual pulses grouped in trains.
The trains have a frequency of 10 Hz, with a timing precision of sub ns.
The pulses have a frequency of 2.2 MHz with a timing ...
0
votes
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
votes
1answer
44 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
votes
6answers
990 views
Use of the Dirac delta as a sampling operator
As we are all taught in signal processing classes, the Dirac delta is not a normal function but a generalized function. It is sometimes defined as either the limit of some normal function whose ...
2
votes
3answers
237 views
Sampling Theorem and Signals Explained to a Mathematician
Let $f:\left(-\frac T2,\frac T2\right)\to\mathbb{R}$ for some $T>0$. The Fourier coefficients of $f$ are $$\left\{\begin{matrix}a_0&=&\displaystyle\frac 1T\int_{-T/2}^{T/2}g(t)\;dt\\a_k&...
3
votes
2answers
154 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 ...
1
vote
1answer
1k views
Sampling Rate Effect on Quantizer SNR
I am currently reading the 'Coding' chapter on Rabiner & Schafer's Book on speech processing.
In one of its exercises, the reader is given a simple A/D converter using 16-bit uniform ...
0
votes
1answer
50 views
Zone Plate Reconstruction
I am trying to reconstruct the Zone Plate image and am struggling to remove the last remaining aliasing.
ShaderToy: https://www.shadertoy.com/view/wdGGWK
In the shader above you can see that I am ...
0
votes
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
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....
0
votes
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.
...
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 ...
9
votes
2answers
932 views
Compressive Sensing vs. Sparse Coding
There apparently are different terminologies used to refer to the same field called "compressive sensing" such as (see this wiki page): compressed sensing, compressive sampling, or sparse sampling. I ...
0
votes
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 ...
0
votes
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
votes
1answer
70 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).$$
If the sample period is $T_s = \frac{\pi}{60}$ then according ...
0
votes
1answer
46 views
0
votes
1answer
88 views
Sample-rate, filtering, digital-filtering and aliasing
I am strugling with a question that I hope someone can help me with.
I am recording single molecule events which I detect is picoampere square deflections.
I wish to use as gentle low-pass bessel ...
0
votes
0answers
25 views
removing noise using Scipy.signal.butter:
I am going to remove the noise from a brain recorded signal. It was a continuous recording and with sample rate=30kHz, it was digitized. So now it is a digital signal.
I have written the code here ...
0
votes
1answer
48 views
Trouble with understanding moving average filter as an oversampling filter
I am struggling with understanding how an moving average filter can increase ENOB in a given sample.
I wrote a test for a simple MA (moving average) filter in matlab. The algorithm to create new MA ...
3
votes
1answer
435 views
Bridging CTFT and DTFT for a cosine
I'm trying to understand how I can start from the CTFT of a signal and end up with a DTFT.
For example if I take a basic example:
$$\begin{aligned}
x(t) &= \cos(\omega_x \cdot t) = \frac{1}{2} \...
0
votes
1answer
59 views
sampling a continuous time signal using MATLAB?
I have a continuous time signal $x(t)=cos(2 Ļft)$ 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
votes
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
votes
2answers
63 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
2answers
94 views
Sample Rate & Highest Frequency
Would I be right in saying that if a signal was sampled every 0.2ms, when converting it to digital. The sampling rate would be 5000(Hz)?
How would I go about working out the highest frequency it ...
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 ...
1
vote
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 ...
0
votes
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)$...
0
votes
2answers
100 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 ...
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}{...
3
votes
2answers
14k views
What is the difference between cubic interpolation and cubic “Spline” interpolation?. How to use it for upsampling purpose?
After considering a couple of advices and suggestions for upsampling techniques here, I finally converged to use the cubic interpolation technique to estimate the voltage values corresponding to ...
0
votes
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 ...
0
votes
1answer
42 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
vote
1answer
390 views
Are resolution increase and noise reduction from oversampling mutually exclusive?
Oversampling a signal means sampling it with a significantly higher sampling frequency than the Nyquist rate. As far as I know, there are three advantages:
Easier design of anti alias filter
Increase ...
