Questions tagged [sampling]
In signal processing, sampling is the reduction of a continuous-domain signal to a discrete-domain signal.
699
questions
0
votes
1answer
47 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
53 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
votes
0answers
22 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
votes
1answer
20 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
61 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
62 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
92 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
52 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
40 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 ...
0
votes
0answers
29 views
Signal to Quantization noise problem
a full scale signal of bandwidth 5 khz is sampled by an 10-bit ADC at a sampling rate of 2 Msa/sec
calculate the Signal to Quantization noise of the resulting DT signal
repeat for a 14-bit ADC at ...
0
votes
0answers
31 views
FFT first frequency
I have some problems understanding FFT. If I know Fourier analysis frame (1024 samples) and sample rate (48 000 Hz), how can I find the first frequency of harmonic sines and cosines?
2
votes
1answer
47 views
How to describe correlated noise after the signal is oversampled?
The Gaussian noise in discrete signal models is usually assumed to be independent and identically distributed variables (i.i.d.). Does this mean that the signal must be sampled with the sampling rate ...
0
votes
1answer
57 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 ...
0
votes
0answers
16 views
DTFT based Frequency Sampling
H($e^{jw}$)= 1, |w| < $\pi/2$ and 0, $\pi/2$ <= |w| <= $\pi$
I took M equally spaced frequencies from 0 to $2\pi$. If we assume h[n] to be causal, $H(e^{jw})$ should have some phase and it'...
0
votes
1answer
28 views
Band-limited signal recovery with finite bit depth
The sampling theorem tells us that a signal with no frequencies above $f$ can be completely described by sampling it a rate of $2f$. However, the theorem makes no reference to quantization, and so I ...
0
votes
0answers
42 views
Analog-to-Information Converters?
In Analog-to-Digital Converters(ADC), the signal is first sampled at a rate higher than or equal to the Nyquist, then quantized and encoded. In Analog-to-Informations (AIC), the sampling and ...
0
votes
1answer
68 views
1
vote
1answer
31 views
Sampling a signal with varying frequency
Question
I'm trying to figure out the sampling rate for my ADC to sample essentially signal essentially of the form:
$$y(t) = \sin(\max(t, \omega_{max})\times t) + n$$
where $n$ is noise.
Context
...
2
votes
1answer
47 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
21 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
1answer
51 views
with given Sampling rate, what max frequency human voice can be captured?
I'm new to signal processing and sampling rate, I was asked interview question related to this.
This is the exact question asked:
With 8Khz of sampling rate, whats the max frequency that human ...
1
vote
1answer
108 views
When calculating SNR, is noise included in signal?
Given a signal $x(t) = s(t) + n(t)$ where $s(t)$ is the desired signal voltage and $n(t)$ is the noise, should the signal to noise ratio of this signal be 20log(xrms/nrms) or 20log(srms/nrms)? i.e., ...
0
votes
1answer
31 views
$x[n]$ after sampling of $cos(16\pi t+\phi)$ at 12kHz
I'm not sure what the question really means, so this is just guesswork.
I think options 1 and 4 can be ruled out as $w_0<\pi$.
The CTFT of $cos(16\pi t+\phi)$ has two spikes at $16\pi$ and $-16\...
1
vote
0answers
25 views
Find integral of DTFT after sampling (Graph of CTFT given)
So for the first question:
If this is sampled at 10kHz, then the amplitude is scaled by 10000. In the DTFT, the frequency 3.5kHz gets mapped to 3.5/10* 2pi=0.7pi. So this point lies outside the range ...
1
vote
1answer
35 views
Find $X(j\omega)$ after sampling of $2\cos(2000\pi t)+\sin(5000\pi t)$ at 5 kHz sampling rate
The Fourier transform of the first term has two spikes at -2000pi and 2000pi of magnitudes 2pi for both.
The Fourier transform of the second term has two spikes at 5000pi and -5000pi having ...
0
votes
1answer
44 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
2answers
37 views
Passing a sampled signal through a filter
I was wondering why is it wrong to use a band-pass filter on a sampled signal?
If the signal we want to sample has frequencies up to fmax, we sample it with frequency fs = 2fmax (so that Nyquist ...
-1
votes
2answers
81 views
Derivation of Nyquist Frequency and Sampling Theorem [closed]
I have been looking through different sites and questions over the internet about Sampling theory, but couldn’t find the clear definition of how nyquist frequency condition is derived? It would be ...
0
votes
1answer
32 views
Inverse Fourier Transform Dirac impulse with scaled argument
Currently, I am dealing with the sampling problems and I don't understand how to calculate inverse Fourier transform of a scaling impulse function
$\textrm{IFT}\{\delta(\Omega T)\} = ?$, $T$ is ...
2
votes
0answers
56 views
Problem with 1st order PLL update equation
The output of a communication channel is given by:
$x(t) = \sum_n{a_n}h(t-nT)$,
where $\{a_n\}$ are BPSK symbols, $h(t)$ is the channel response, and $T$ is the symbol period. If there is an ...
0
votes
0answers
47 views
A Different Reconstruction Operation
I want to understand what is happening in below operation:
Here, x(nT) is sampled signal (say oversampled) and h(t) is its ideal reconstruction filter. As highlighted in the expression, amount of ...
0
votes
1answer
63 views
Conclusions of sampling around Nyquist Rate
I'm trying to understand some results of playing around with sampling around a signal's Nyquist sampling rate. For my example, I'm sampling a $B=5\mathrm{Hz}$ wave over a 1 second period.
In the ...
3
votes
1answer
46 views
Representing a continuous LTI system as a discrete one
I am aware that there are different ways to represent a continuous time system in discrete domain (e.g. bilinear transform, impulse invariance transform).
But my problem is as follows: Given an ...
0
votes
1answer
56 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 ...
0
votes
2answers
93 views
Proof regarding the periodicity of a continuous-time sinusoid after sampling
Question
A continuous-time sinusoid $x_a(t)$ with fundamental period $T_p = \frac{1}{F_0}$ is sampled at a rate $F_s = \frac 1 T$ to produce a discrete-time sinusoid $x(n) = x_a(nT)$.
Show that $x(n)$...
0
votes
1answer
85 views
Kalman Filter - How to combine data from sensors with different measurement rates?
I'm trying to implement a Kalman filter for tracking the position of a vehicle with the help of position data from GPS and Odometry measurements. The GPS data (WGS84 format collected from an app on an ...
0
votes
2answers
91 views
Minimum sample frequency of IMU accelerometer and gyroscope
I was wondering how I would justify a sampling rate of 125 Hz for accelerometer and gyroscope data from wearable sensors. This is a rate used in a lot of biomechanics literature, but I can't seem to ...
1
vote
1answer
60 views
Why does my sinusoid look “AM” in shape?
My code is :
Fs=200e6;
Ts=1/Fs;
NFFT=2^14;
Runtime=(NFFT-1)*Ts;
t=0:Ts:Runtime;
f_in=90*1e6;
y_in=sin(2*pi *f_in *t);
plot(t,y_in)
ylim([-1.5 1.5])
Then why does ...
4
votes
4answers
729 views
Is Fourier series a sampled version of Fourier transform?
I recently learned about dtft and how dft/dfs is the sampled version of dtft. I was wondering if Fourier series is also obtainable by sampling Fourier transform? I am a noob in the subject so sorry if ...
0
votes
1answer
57 views
Better understanding of downsampling (decimation) and upsampling (interpolation)
Although some questions were asked about this topic, I have not seen any that answers all the basic questions, that is why I took the liberty to ask more about this.
I suggest to limit, (or at lest ...
2
votes
2answers
146 views
How would you interpret the pattern in this picture? (generated by re-sorting pixels based on their RGB value)
Was playing with some pictures and ran the ruby code below. The code reads an input image using the ImageMagick library, gets an array of pixels, re-sorts the pixels and then writes out an image with ...
2
votes
2answers
72 views
Understanding Pitch Detection with Autocorrelation Methods
I've been reading through A Smarter Way to Find Pitch, describing its pitch detection algorithm using autocorrelation.
I've been having trouble understanding the accuracy claims. It says:
MPM runs ...
0
votes
3answers
65 views
Analyzing a signal that contains frequency content at Fs/2 doesn't seem to work unless there is a phase shift
I am trying to write a basic program that samples a 4 kHz sinewave at a sampling rate of 8 kHz and takes the FFT of the signal and plots it.
From everything I have read, as long as the signal you are ...
0
votes
1answer
105 views
Low-Pass Filtering of not evenly sampled signal
I have a signal sampled unevenly over 1 million ns.
the signal is sampled over 1GHZ clock and the samples are as the following:
0-100 ns - sample every 1 ns.
100-1000 ns - sample every 10 ns.
1000-...
0
votes
0answers
40 views
Cascading filters at different sampling rates
We are currently designing a type 2 compensator $G_1$ (1 pole at the origin, 1 zero and 1 pole) to stabilize a power factor correction (PFC) circuitry. The crossover frequency is low - 2-3 Hz - and ...
1
vote
1answer
39 views
Multiband undersampling
In Practical Signal Processing (Marc Owen), an exercise explore the topic of undersampling:
[...] Suppose you know that an audio signal is a sine wave with a frequency that might be in one of two ...
5
votes
1answer
63 views
Model-based Kalman filtering a noisy signal
In a healthcare application, I need to calculate urine flow by differentiating the mass of urine emitted by a person over time. The measuring instrument consists of a load-cell under a fluid container,...
0
votes
0answers
97 views
Understanding Upsampling Filter in Laplacian Pyramid
For the construction of a laplacian pyramid, images are downscaled and then upscaled again. My question is what is a wise decision of the kernel mask for the upscaling task ?
In more detail, lets say ...
0
votes
1answer
32 views
Sampled AC Voltage measurement
I want to implement a AC Voltage measurement function for a DMM. That DMM can sample up to 1,000,000 Samples/s.
With the sampling function I wanted to sample an input sigal (e.g. sine signal) and ...
3
votes
3answers
217 views
Should I sample at twice the bandwidth or twice the highest frequency?
I am confused about what rate I should sample at. I've heard 2 different ways:
1) Sample at twice the highest frequency
2) Sample at twice the bandwidth
If I have a signal composed of just cosine, ...
