Questions tagged [nyquist]
The nyquist tag has no usage guidance.
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Ratio of aliased to desired energy of a sampled signal
In this article "Sampling: What Nyquist Didn't Say, and What to Do About It" from Wescott, the author shows in Figure 6, the plot of the frequency spectrum of a signal which goes through a ...
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Is there a test/statistic for the reliability of my data given my sampling?
I'm in a situation where I'm sampling blood pressure data over time (unequal sampling) to capture potential peaks. On average, the frequency of circadian blood pressure would be 1. But in reality, ...
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Combining two time series with different cadences (different Nyquist frequencies)...?
If it helps, I want to do perform the below computation in python.
Two time-series - 30-min cadence (Nyquist of 24 cycles / day) lasting 27 days, followed by 10-min cadence (Nyquist of 72 cycles / day)...
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modulation transfer function and ground resolved distance
I am trying to understand something in remote sensing but lack a background in science and technology so it is difficult. Hopefully this is a reasonable question to ask.
In sensing there are different ...
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Sampling a sinusoidal signal smaller than Nyquist rate
If we have a sinusoidal signal at 50 kHz and we sample it by an ADC with a sampling rate of 7 kHz. What would be the output of the ADC?
Since the sampling rate is way less than the Nyquist rate (...
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Choice of $N_{terms}$, frequency grid in Lomb-Scargle periodogram
I am completely new to signal processing! Please explain as if speaking to someone who knows nothing more than linear algebra and what a Fourier transform is defined as.
I am working with an 8-month ...
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Find constants such that the Nyquist criterion is satisfied [closed]
I have been given the following spectrum, and I want to find a and b such the pulse satisfies the Nyquist criterion, given that the bandwidth of the pulse is 2 kHz and the sampling frequency is 3 kHz. ...
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How to compute the ifft of a constant value?
I am clearly missing something obvious here because I am trying to do something that ought to be very simple: compute the ifft of a continuous signal.
My understanding is that the ifft of a continuous ...
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Time-interleaved ADCs, Nyquist zones et al
I am trying to decipher some notes on a Time-interleaved Analog-to-Digital Converter with 4 sub-ADCs (the author is unreachable at the moment), but there are few things obscure to me so I was hoping ...
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recreating nyquist regions using FFT python
using python I have sampled a signal and made FFT to see the spectral picture of the time domain signal.
the plot bellow shows only 1st and 2nd nyquist zone.
I want to expend the spectral image and ...
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A problem about SQNR, PCM, DPCM, and DM
A baseband analog message signal $x(t)$ with bandwidth 20 kHz, power
$10^{-3}$, and $|x(t)| \leq 1$ is waveform encoded and transmitted
through a channel of bandwidth 160 kHz. Besides, let the sampled ...
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Question about Nyquist sampling - filtering of high image copies
Suppose I sample an audio signal with a sampling frequency > twice the highest audio frequency.
ie, the frequency transform of the sampled signal looks like the image on top here, where there is no ...
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How do I match a filter to an AWGN channel?
I have the task to find a transition that fulfills the first Nyquist Criterion. After that I am supposed to match that filter to an AWGN channel. For the first part I thought a raised cosine ...
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LTI Filter for DAC Reconstruction
$\textbf{Question:}$ An analog-to-discrete is designed as,
$$x[n] = x_a(nT)$$
In an attempt to recover the analog signal from its samples x[n], a D/A converter is designed as ,
where $x_1(t)$ is ...
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Why does the bandwidth of a signal need to be half of the sampling rate? [duplicate]
Suppose I perform a DFT on some function with sampling rate of $\frac{1}{\Delta t}$. According to this page, the bandwidth, which is the maximum frequency that can be analyzed when performed the DFT, ...
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Moving average before downsampling: effect on Nyquist frequency?
First the simple questions:
Is there an effect on the Nyquist frequency when I apply a moving average filter on the raw data before I downsample?
And what does this do to aliased frequencies?
...
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Discrete Fourier Transform of real valued input using half the amount of frequency bins
Quick question:
Is it correct to define Discrete Fourier Transform like this, if my input signal is real valued:
$$
X[k] = \sum_{n=0}^{N-1} x[n] \cdot e^{-i2 \pi n \frac{k}{N}}
$$
Where $k \in \{0, 1, ...
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Nyquist frequency Plotting Distortions
I'm trying to plot some sinusoidal signals in Matlab.
But while frequency is getting higher (closing to fs/2), results are getting distorted.
I guess it's lack of my knowledge but distortion is ...
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Is there a way to compute the spectrum effect of a non-linear function?
I'm interested in developing audio software. I've read the books by Will Pirkle and there's something I'm struggling to understand about how non-linear functions affect the frequency spectrum of a ...
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Filter amplifies frequencies at nyquist frequency. What's the purpose of such a filter?
I'm currently facing a filter that amplifies frequencies at the Nyquist frequency. The sampling frequency is $f_s = 10$ Mhz.
What's a typical application for such a filter?
This is how I generated ...
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How does a CIC filter output meet Nyquist?
In this image from Understanding cascaded integrator-comb filters
The bottom image shows the output response, with the entire range as passband:
Even the CIC compensation filters are all passband to $...
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Is the slow waveform an alias - and why don't we see other alias'es of different frequencies?
The following figures are data from sampling the DC bus of an inverter for a BLDC/PMSM drive running a speed-loop with FOC.
The upper subplots are FFT's of the signal and the lower subplots are of the ...
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Are there any recommended filter types for passband frequencies near Nyquist?
Is there a recommended filter type for frequency bands near the Nyquist frequency?
I have been trying to design complex passband filter with passband $[0.8 ~~1]$ ( where $1$ corresponds to the ...
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Why are real-world digital images not bandlimited?
In the materials about image resampling, it always mentions that real-world digital images not bandlimited. However no explanation
is provided.
For example,
Sinc resampling in theory provides the ...
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167
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Having Nyquist bin = aliasing?
Here I motivate the question by deriving FFT upsampling for $N \rightarrow 2N$ with even $N$.
One might naively try xup = 2*ifft([xf[:N//2], zeros(N), xf[-N//2:]]), ...
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How is the maximum theoretical data rate of a channel equal to $2B\log_2(V)$ bits/sec.?
According to Andrew S. Tanenbaum (in "Computer Networks", Chap. 2, Section 4 "The Maximum Data Rate of a Channel"), the Nyquist/sampling theorem states that "if an arbitrary ...
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How to choose correctly oversampling ratio?
As many of us have noticed, last two months I am working on GMSK modulation and demodulation design. Before continuing my research, I want to be sure I chose the correct oversampling ratio ( how many ...
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Reconstructing a signal from a Nyquist plot
I have a system which is like a blackbox which has just one input which could be a sinusoidal wave which is a sum of a range of frequencies, now the problem is that I dont have the time-domain output ...
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What does the two following formulas mean?
I am a bit confused between the following two formulas:
$$ f\le \frac{f_s}{2} \tag{1}$$
and:
$$ f = \frac{f_s}{N} \tag{2}$$
Now I am given an ACF Plot of a sine/cosine wave and I am asked to find ...
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How do we determine the required sampling rate of a closed loop control system?
Consider the controlled dynamical system $\dot{x}_t = f(x_t, u(t-\tau_{sd}))$, where $0<\tau_{sd}$ denotes the time delay caused by sampling. It is intuitively clear that the time delay caused by ...
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What is the output signal's frequency when doing operations of two signals?
If I have two continuous time signals x(t) and y(t) of maximum frequencies Ω1, Ω2 respectively. I want to find the sampling frequency used used in continuous-discrete conversion of the following ...
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How do I determine the dominant frequency of a signal after sampling?
For example if I have a $10 Hz$ signal and I sample it at $19 Hz$ (less than the Nyquist frequency) how can I determine the dominant frequency of the output and why?
If I then apply a lowpass filter, ...
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Sampling, filters, windowing, FFT. From theory to help on this coding list
My plan is to analyse the spectrum of samples from a microphone.
I wonder how correct this suggestion is. The below description may then fail on several points. I am in need of somebody with a red ...
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Stanford EE 261 HW6 Q1 - Sampling below Nyquist Rate
The problem (taken from here) asks for possible sampling rates that will not cause aliasing in the following frequency spectrum:
The range of possible values after some math is given as $B_2 < f_s ...
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Given a signal that is not bandlimited, how do you properly take the FFT?
I assume that the Nyquist theorem doesn't apply, at least not in the standard sense, for a non-bandlimited signal. In my case, I sample the signal (in the time domain) above the Nyquist rate and then ...
user62718
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In what cases can you get aliasing below the Nyquist frequency?
I took the one-sided FFT of a signal and plotted up until the Nyquist frequency. Then, I took the real part of this FFT multiplied by $i\omega$ following a calculation that I'm trying to do of a ...
user62718
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Matching Filter & Raised Cosine Confusion
I'm reading from Communication Systems, 5th Edition by Simon Haykin. At some point we derived that
Which is how the effect due to AWGN is minimized. Meanwhile, to minimize ISI we need $P(f)$ to be ...
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The raised cosine spectrum and Nyquist's criterion for zero ISI
For the past hour, I've been trying to understand what the book is trying to say here:
This is Communication Systems, 5th Edition by Simon Haykin.
We know that the Nyquist criterion is
I'm unable to ...
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Inferring shape of information signal from its DFT?
I came across this question recently, and I am very confused by (b)(ii).
b(i) gives $x_n$ = [0.5, 0, -0.5, 0].
My approach to (ii) was to recognise that $X_m$ represents the frequency content of the ...
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What is the symbol rate achieved with raised cosine filter?
The bandwidth of the raised cosine filter is w=0.5(1+r)Rs, where Rs is the symbol rate, and r is the roll-off factor. r=0 represents the Nyquist filter, for which Rs=2w.
Any higher value for the roll-...
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Will or can a sampled signal with a limited sampling frequency have infinite bandwidth?
I know that a continuous-time digital signal with sharp edges (e.g. jumping from one y-Value to another discontinuously at the same x-value) will have infinite bandwidth. But what about sampled ...
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does T = 1/F always hold?
i just want to know if i use a sampling frequency of 100-110Hz and get a useful signal frequency of 50Hz (because of Nyquist–Shannon sampling theorem), is the period 1/50Hz or 1/100Hz?
I've been told ...
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Sampling frequency vs Signal frequency
I've started recently working with the ADXL345 accelerometer with the goal of finding the velocity.
And so far, I'm getting "okay" results after applying a second-order Butterworth filter to ...
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Sampling with Rectangular Pulse and Nyquist Condition
The classical Nyquist theorem assumes that the sampled signal is obtained by multiplying the signal with dirac-delta functions separated by width 1/f_sample or less. Given such sampling we can ...
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Aliasing in continous-time signal
I have the following signal and it was plotted with a sampling frequency (Fs) of 5Khz and F0 was then varied for 0.5Khz, 2Khz, 3Khz, and 4.5Khz. I obtained aliasing when F0 = 2Khz and 3Khz only.
...
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Why is the bandwidth of each ZigBee channel in the 2.4GHz frequency band 2MHz, while the sampling interval of the ZigBee receiver is 0.5us? [duplicate]
From the Wikipedia, the XBee paper, the BlueBee paper, and the WeBee paper, I learned that:
In the 2.4 GHz band, the bandwidth of each ZigBee channel is 2 MHz.
For receiving a signal over one of ...
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ADC sampling of incoming signal and aliasing effect [duplicate]
I know from the sampling theorem, that the signal frequency $f_{sig}$ shouldn't exceed 0.5 of sampling frequency $f_{samp}$.
I decided to have a look at it and tried for example $f_{samp} = 50 $ $kHz$ ...
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Misunderstanding of Nyquist sampling theorem and minimum sampling rate
I sample my time-domain (TD) signal using a distance between time-samples of $\delta = (t_{max} - t_{min}) / N_t$, where $N_t$ is the number of samples taken. The sampling rate is $1 / \delta$.
I have ...
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What sampling frequency should I use if Nyquist is not available?
I have the following homework question that confuses me:
We have an audio emitter that can emit two signals:
It either emits a sine wave at 23 kHz or it emits a sine wave at 25 kHz.
The receiver has ...
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The minimum frequency for signal modulation
I have a signal sampled with frequency 10 kHz. My spectrum is 1 kHz.
As far as I went, according to the Nyquist theorem I can module the signal with max. 5 kHz (1/2 of sampling frequency).
What's the ...
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