# Questions tagged [nyquist]

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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)...
1 vote
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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 ...
1 vote
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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 (...
1 vote
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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 ...
1 vote
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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 ...
261 views

### 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 ...
157 views

### 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 ...
1 vote
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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, ...
1k views

### 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? ...
1 vote
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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 ...
72 views

### 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 ...
249 views

### 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 ...
167 views

### 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 ...
160 views

### 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 ...
1 vote
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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 ...
1k views

### 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 ...
1 vote
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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 ...
718 views