Questions tagged [sampling]
In signal processing, sampling is the reduction of a continuous-domain signal to a discrete-domain signal.
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decomposition of a function to piecewise functions
Is the next answer correct:
$$a\left(z\right)=\sum _{\left\{k\right\}U\left\{k'\right\}:f_k\le \:z,\:z\:\in R,\:f_{k'}\ge z\:;\:z\ge 0}1-\frac{f_k}{z},\:b\left(z\right)=\sum _{\left\{k\right\}:f_k>...
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1answer
43 views
Is Sum of Absolute Value / $ {L}_{1} $ Norm of Differences Convex?
I'm not sure how to approach this exercise.
One idea is to derive it w.r.t z, show that there is a min-extremum at $z=f_k$ and then show that for each value from the right and the left of the loss ...
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23 views
sampling using L1 optimization
As much as I understand the F should be the interval medians (correct me if I wrong), according to the next slide, where is also the Loss function defined:
What I don't understand is the next note in ...
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1answer
35 views
Quantization and Sampling - putting it all together
So after I learned this two topic: quantization and sampling, I'm learning the way to look at both of them and try to optimize the split of a given amount of bit B to N and k, where N is the amount of ...
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23 views
NUFFT of non-uniformly sampled signal
I am trying to understand how to use nufft from the Matlab doc.
My goal is to compute a FFT of an image (2D) which has missing points (not sampled). I have a list x and y of coordinates of the points ...
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2answers
43 views
The peak in frequency spectrum from sampled data is higher than the true amplitude
I am given a task to do sampling on the function
$$f(t) = 1.3 \sin(2\pi \cdot 10 \cdot t)$$
with sampling frequency 4 Hz and start at time t_start = 0.0877s, so ...
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1answer
42 views
Relationship between amplitude and sampling rate
I'm loading a signal with librosa in python. With the original sample rate of 22050 Hz, i get the following waveplot:
When i choose to resample my signal with the sample rate of 512 Hz, i get the ...
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20 views
Response time of residual current device and sampling times
The table below is from this document: Schneider RCD
When the maximum response of the device is 40 mS, does it measure current doing RMS or peak detection? The document does not explicitly say it. ...
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1answer
23 views
Impulse invariance vs. DT representation of a CT system: Where is the inconsistency?
Suppose you have a continuous-time (CT) system $h_c(t)$, bandlimited to $B$. Your goal is to represent the system as a discrete-time (DT) system $h[n]$, sampled at $f_s \leq 2 B$. Clearly $h[n]$ won't ...
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207 views
What can be meant by “bandlimited”?
This question was a source of disagreement on whether "amplitude aliasing" can occur for a signal bandlimited to below half the sampling frequency. The question was closed before the ...
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2answers
364 views
Amplitude modulation vs sampling rate? [closed]
As a sampled tone's frequency nears $f_s / 2$, amplitude modulation grows apparent:
("Actual" curve in grey; blue is what we get if taking samples (dots) "at face value"). This is ...
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2answers
50 views
Coherent Sampling vs Windowing for 50/60 applications
Let's say I need to sample 50/60 Hz signals to find RMS. I can use for example 1kHz sampling frequency. That means 100ms sampling is 5 cycles of 50Hz and 6 cycles for 60 Hz. That's coherent sampling. ...
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2answers
284 views
Increasing SNR and Dynamic Range using Oversampling
How much gain in dynamic range and SNR can be expected if we are to oversample a signal with fixed analog input bandwidth. For Example if I have a analog filter at the input which limits the bandwidth ...
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1answer
71 views
Aliasing at $f_0 + kf_s$
In this question, it has been proved that $x(t) = \sin(2\pi f_0 t)$ and $x_k(t) = \sin(2\pi (f_0 + k f_s) t)$ have the same sample points. So sinusoids with frequencies $f_0$ and $f_0 + kf_s$ will ...
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39 views
Sampling frequency error in OFDM [duplicate]
If the sampling rates at receiver and at transmitter are different, there will be ICI.
However I don't find any practical technique to estimate and compensate this kind of error. Is it true that we ...
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1answer
60 views
Inverting a sampled system
I'm doing some self-study for an upcoming exam and came across the following question:
My first idea to solve it was using the bilinear transform to get some approximation of $H(Z)$ (or just using ...
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fo we need RMS in SNDR of harmonic distortion
In my system we have the following.
$$V_{in}=1+\cos(2\pi 900,000)$$
$$V_{sample}=V_{in}-0.01V_{in}^2$$
$$V_{noise}=200 \times 10^{-6}V$$
After the input i get in $V_{sample}$ the following ...
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1answer
48 views
why we do multiple aliasing of high order harmonics
the general rule for aliasing.
If my sampling frequency is Fs=800Mhz
signal frequency =120Mhz.
for the 4th harmonics 480MHz
its 80MHz above nyquist frequency(400Mhz) thus its mirrored 80MhZ back to ...
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27 views
Goertzel filter for non-equidistant sampling
We have a sensor that reports a new value asynchronously only when the value changes. Therefore, we receive samples at arbitrary time stamps. We basically receive value + timestamp of the measurement ...
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2answers
41 views
Why negative harmonics copies in sampling
i have a signal of 120Mhz and sampling at 800Mhz. we look at the region of fs/2=400MHz so obvios we have harmonics of the fundamental which is 240 360. But in the document i see that there is another ...
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1answer
86 views
Multiplying signals in discrete-time vs continuous-time
Given two discrete-time signals $a[n]$, $b[n]$ and its product $c[n]=a[n] b[n]$. The ideally interpolated, continuous-time version of $c[n]$ is
\begin{align}
c_1(t)&=\sum_{n=-\infty}^{\infty} a[n] ...
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1answer
71 views
Sampling Dirac function and a DC signal
Can we sample the Dirac function?
$$ x(t) = \delta(t) $$
Can we sample a DC signal?
$$ x(t) = 1$$
I think that we can't sample $x(t) = 1$ because the Fourier Transform of $x(t) = 1$ is $2\pi \delta(...
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3answers
94 views
Downsampling vs. ADC with lower Sample-Rate
I would like to know in general where the advantages and disadvantages are:
Downsampling of a high sampled continuous analog signal in FPGA or µC and
Direct use of a lower sampling rate, i.e. using ...
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0answers
55 views
What is the multiplication rate in FIR filter
Consider a system implementing a rational sampling rate change by 5/7: for this, we cascade upsampler by 5, a lowpass filter with cutoff frequency pi/7 and a downsampler by 7. The lowpass filter is a ...
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2answers
113 views
OFDM sampling frequency offset
how the 4G LTE Or 5G NR OFDM measures and corrects the sampling frequency offset? if there is an algorithm using matlab please help
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0answers
28 views
Showing that filtering a signal with bandwidth B with a brickwall filter of bandwidth W>B has no effect in time domain
The time-domain representation of $G(f) H(f)$, where $H(f)$ is an ideal brickwall filter of bandwidth $1/(2T)$ is:
$$
\int g(\tau) \operatorname{sinc}\left(\frac{t-\tau}{T}\right) d\tau
$$
I want to ...
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2answers
97 views
Can I sample at Nyquist rate if I know that my samples are taken only at the signal's maxima or minima?
I know that in general the sampling rate, $f_s$, must be greater than twice the highest frequency of the signal, $f$.
If I sample at the Nyquist rate, it can lead to the following:
However, if the ...
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1answer
108 views
Is spectral density sometimes normalized by sampling rate rather than bin size?
I'm a scientist conducting an experiment that requires some signal processing. My expertise is not in signal processing, thus here I am. We've basically re-created an experiment conducted by other ...
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1answer
93 views
number of multiplications per second required by the system
Consider a system implementing a rational sampling rate change by 5/7: for this, we cascade upsampler by 5, a lowpass filter with cutoff frequency π/7 and a downsampler by 7. The lowpass filter is a ...
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0answers
46 views
How to characterize the randomness of an event using it's PSD?
I have the power spectral density function of a stochastic phenomenon.
how can I generate a signal (time series) representing the randomness of this event over time?
How can I draw the probability ...
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0answers
70 views
minimum oversampling factor for D/A converter
Consider a D/A converter for audio signals consisiting of a zero-order-hold interpolator followed by a continuous-time lowpass filter with positive passband between 0 and 20KHz and stopband starting ...
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1answer
177 views
the number of multiplications per second required by the system
Q1. Consider a system implementing a rational sampling rate change by 5/7: for this, we cascade upsampler by 5, a lowpass filter with cutoff frequency π/7 and a downsampler by 7. The lowpass filter is ...
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3answers
94 views
How to distinguish between FFT power leak or close frequencies
This week I was having an interview with a Professor for Grad School. He asked a bunch of questions related to signal processing that lead up to some questions about power leak on the FFT spectrum. So ...
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2answers
79 views
D/A converter with
I am trying to figure out how to consider digital-to-analog conversion and how to consider oversampling based on a course I am taking online and figuring out the logic behind this. Unfortunately there ...
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2answers
47 views
How to reconstruct a time-discrete signal
German: Sie betrachten das zeitkontinuierliche Signal $s(t)$ mit einem digitalen Oszilloskop mit Abtastperiode $T_\mathrm{s}$ und messen das zeitdiskrete Signal $\tilde{s}[n] = s(n\:T_s)$
Nehmen Sie ...
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down sample and up sample
Does these codes hold true for up sampling and down sampling processes?
...
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24 views
Confusion in property of Z transform of ideal sampled waveform
I was reading about z transfom of ideal sampled signals and one of the properties of Z transform of sampled signal that surprised me,here it is (image)
So here this property of Z transform is quite ...
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2answers
89 views
Correction of amplitude after zero padding for upsampling purposes
I have time sequence in which the data is sampled at 0.8 Hz. The data is related to chromatography (chemical analysis), that is why the sampling frequency is relatively low. The instrument cannot ...
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35 views
Variable Window Size of Blackman FIR filter
I am trying to implement an FIR filter with a Blackman window function. The solution I got for my signal filtering problem is to have different window sizes for certain characteristics of the input ...
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1answer
59 views
Oversampling, decimation and Nyquist
I know this is a bit of a fundamental DSP question but I want to finally understand this and I think I need some help to finally put it all together.
Let's say I have an RF complex sampling ADC with a ...
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1answer
42 views
The impact on the frequency of adding zero samples and non zero samples
Can someone give me a brief explanation of what is going on in here? I struggle to understand the full differences between the impact on the frequency of added zero samples and adding samples which ...
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1answer
46 views
Cosine of amplitude 1 but GNU Radio shows FFT has amplitude > 30,000
I am doing an FFT on a cosine wave which has an amplitude of 1. The FFT is amplitude is not 1 but over 30,000. What am I missing here?
It's from the GNU Radio FFT wiki page:
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1answer
123 views
How to save Fourier series approximated signal to a WAV file
I changed this Matlab/Octave code to approximate square wave by using combination of Fourier series and Fejér taper:
...
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1answer
73 views
4G LTE Sampling Frequency Offset
Could someone please explain how the 4G LTE OFDM measures and corrects the sampling frequency offset?
I can see a number of algorithms proposed in the literature, but I am trying narrow it down to the ...
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Find the frequencies present when a non-sinusoidal wave is reconstructed
A 1.6kHz periodic (not sinusoidal) signal contains all its harmonics, both even and odd. The signal is sampled at 3.6kHz and ideally reconstructed. What frequencies are present in the output?
I know ...
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1answer
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Modulation upsampling method
I try to implement a qpsk modulator in Octave.
The chain is the state of the art I guess: Mapper -> Upsampling x4 -> Root raised cosine filter.
My main question is about the upsampling.
I try to ...
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0answers
19 views
Filtering a noise of F[sig] frequency [Example 20Khz] in measurement system
I am developing a system where there is inherent noise of F[sig] frequency. This is a DC measurement system and want to get rid of the noise by sampling at F[samp] samples per rate and taking multiple ...
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49 views
Where does the imaginary part of a singnal come from? [duplicate]
So I recently watched this lovely overview of DSP/SDR explaining how demodulation of AM and FM becomes trivial by turning a signal into a complex number. (AM being the magnitude of the number and FM ...
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1answer
31 views
Sampling the Wave Equation for String Vibration
I am having a difficult time understanding the basic principles when sampling the function describing the vibration of a string. Mainly I am confused on given a sampling rate how many samples to take ...
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1answer
32 views
Multisampling of an ADC channel in a PWM cycle in TI C2000
I want to sample an ADC channel multiple times in one PWM cycle.
I can trig any ADC channel in anywhere in my PWM timer counter now. But I want to trig and sample same channel in many times within a ...
