Questions tagged [nyquist]

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Changing the Bandwidth of a signal of fixed Sampling frequency [closed]

If sampling frequency is fixed, how can I generate a frequency domain signal of a particular bandwidth from a time domain signal of dimension $1\times N$? e.g. if $f_s=100\,\text{kHz}$, how can I ...
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1answer
265 views

Reconstruct under sampled signal

I have a signal from a PWM inverter that was sampled at 3,84 kHz. The PWM has a switching frequency of 5 kHz. The pwm signal is feeding an induction motor. If I low-pass filter the PWM signal it ...
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1answer
379 views

what is difference between Alias vs. down sampling? [closed]

could someone help me explain downsampling in the context of Nyquist–Shannon sampling theorem and tell the difference between Aliasing and downsampling.Also is downsampling and undersampling the same ?...
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668 views

Nyquist frequency - Sampling theory

If a signal contains frequencies from $500$ to $1000\textrm{ Hz}$, what is the Nyquist sampling frequency, $2$ times $500$ or $2$ times $1000$? Twice the highest frequency of the signal, or twice ...
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1k views

Determine maximum frequency of input signal to make system LTI

This is question 4.26 from the third edition of Alan Oppenheim's textbook "Discrete-time Signal Processing". It is stated as follows: Firstly, the answer is the input signal should be bandlimited to ...
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1answer
526 views

Digital signal and frequency analysis

I am generating a digital signal with software. I have defined the vector $$[0,1,1,1,0,1,0,1,0,1,0,0,0,0,0,0,0,0,0,0] $$ and my sampling rate is 8 million per second. The frequency spectrum is ...
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2answers
63 views

Minimum recording time for a signal

I am familiar with both Nyquist frequency and Nyquist rate. What I cannot seem to find information on is the minimum time necessary to detect a signal. In my use case I am using a multiplexer to ...
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3answers
423 views

Signal values we will 'miss' between sampling instances during sampling of band limited signals

According to the Nyquist–Shannon sampling theorem, any continuous time signal with a bandwidth $B$ smaller than Nyquist frequency $f_N=f_s/2$ (with $f_s$ the sampling frequency), which is sampled at ...
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1answer
220 views

Noise Peaks Near Nyquist Frequency

I am working on an audio upsampling/oversampling project where I am testing different interpolating schemes in hardware and comparing measurements to my expected results. In one of my interpolating ...
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8answers
8k views

Nyquist Frequency Phase Shift

The figure below shows in dashed lines sinusoidal signals of the same frequency at three different phase shifts. The signals are then sampled such that the sinusoidal frequency is exactly a half of ...
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1answer
252 views

Nyquist rate determination and oversampling [duplicate]

I'm new to this. I'm using ShannonGui to generate a sine wave with a $1\textrm{ Hz}$ signal frequency. From what I can tell to determine the Nyquist rate I need to double the highest frequency, since ...
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1answer
879 views

Properties of root raised cosine filter

In communication systems, the transmitted signal is often passed through a root-raised cosine filter to avoid, in textbook language, intersymbol interference (ISI). An identical filter at the receiver ...
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1answer
816 views

Convolving a discrete time sequence with a continuous-time filter?

I am a newbie to DSP, and have what seems to me a fundamental question. I have a discrete-time sequence $g[n]$ of length $N$. I am supposed to pass this signal through a root-raised cosine filter $...
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1answer
879 views

Sampling theory and frequency spacing

If a CT signal $x(t)$ is sampled for one ($1$) second and $4096$ samples are generated: Isn't the highest frequency that can be sampled without aliasing ($4096/2$) $2048\textrm{ Hz}$? If a $4096$ ...
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3answers
409 views

Time Domain Example of Nyquist/Shannon?

I looked at an old thread, Nyquist Frequency Phase Shift, but was left wondering still about oversampling. I learned Shannon 40 years ago, then worked 30 years in (s/w) engineering, but now retired I ...
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1answer
474 views

Elegant way of calculating minimal sampling frequency without aliasing for annoying signals

Given a symmetric Fourier transform with finite support as below, there's an algorithmic procedure to determine the minimal frequency for sampling without aliasing: Find an integer $L>1$ ...
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1answer
243 views

Given a continuous time signal, does the minimum Nyquist sampling rate depend on the choice of the set of basis functions?

This is my first question on a StackExchange. When the basis functions to represent a signal are chosen as $e^{j\omega t}$ such as in a continuous-time Fourier transform then the sample rate $f_\...
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1answer
130 views

What is the maximum allowed transition band of the low-pass filter used in the reconstruction kernel for a CD with maximum speech frequency of 4 kHz?

My question is if the transition band in the question below would be from 4Khz to the Nyquist frequency of 22.05Khz or from 4Khz until 44.1Khz-4Khz=40.1Khz?
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1answer
245 views

Determining the Nyquist rate of signals added and multiplied together

Suppose I have a signal in the frequency domain $x(\omega)$. Suppose I know that its Nyquist rate is $\omega_0$ (and let $\omega_m$ be the its maximum frequency). I need to get the Nyquist rate of $...
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1answer
632 views

Output a sine wave from samples-limits?

Using a micro-processor of 48MHz, I am trying to output a sine wave from the DAC (digital to analog ), and I am not sure if my ...
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2answers
3k views

The relationship between downsampling and frequency resolution

I am having trouble understanding a concept that I have seen in many published papers. For example, in this paper (http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0082748) they wrote ...
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1answer
4k views

Calculating a signals frequency when given the number of samples

This place has been great in helping me to understand my online image and signals class! I've moved on to another question and wanted to see if I'm correctly grasping the subject. The next question ...
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1answer
203 views

What is the LOW frequency resolution rule analogous to Nyquist?

If I'm analyzing a signal in the frequency domain, I know about the well known Nyquist criteria that the sample frequency must be > 2x of the highest component present in the signal. However, there ...
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1answer
52 views

How is the 'max frequency' of a signal fixed?

It is well known that no time-limited signal is frequency-limited. So the frequencies of a time-limited signal extend upto infinity - may be decaying slowly or fastly in frequency domain. But we take ...
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1answer
56 views

Nyquist (Nth) digital filters

I am working in something were I should use a upsampling filter. I have decided to use a Nyquist filter(Lth filter). I know that there are two constraints. The first The frequency vector values must ...
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4answers
305 views

Sampling Theorem: How to know the value between two samples of a Signal

According to Sampling theorem, in order to reconstruct a signal we need to sample it at the rate => twice the highest frequency component of that signal. (provided signal is band limited). Let's say, ...
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Is there such a thing as band-limited non-linear distortion?

So if you generate a square wave by just switching a signal between two values, at sample boundaries, it produces an infinite series of harmonics, which alias and produce tones below your fundamental, ...
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2answers
5k views

Why is a square wave aliased?

I understand an ideal analog square wave contains sine-wave-components above Nyquist frequency (and towards infinity) and is thus subject to aliasing. So obviously we need an anti-aliasing-filter. Or ...
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1answer
555 views

Relation between bandwidth and data rate

I have trouble understanding the following from wikipedia - Bandwidth (Signal Processing) A key characteristic of bandwidth is that any band of a given width can carry the same amount of ...
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1answer
186 views

Find minimum sampling rate of non-ideal notch filter

Old test problem: "You have been asked to design a real-time digital filtering system that eliminates a band of frequencies between 20 and 30 MHz but preserves everything else. The system uses an ...
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1answer
896 views

Choosing minimum sampling frequency of a filtered signal

I have a time series of acceleration sampled at 1000Hz to capture random impacts on a structure. The ringing of the structure (not of interest) produces noise which a 50Hz filter seems to eliminate ...
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1answer
105 views

Sample Frequency - Recommended Practical Nyquist, Lower Used by majorities appications

Doubt1: What is the Lowest Sampling Frequency used by majorities sound applications. Is there limited frequency sampling lower than 8KHz In C/C++? Comment In Java I haven't detected any problem, but ...
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5answers
681 views

Regarding the Nyquist Criterion

I recently read that with compressive Sensing it possible to sample the signal at a rate lesser than that suggested by Nyquist Criterion. However, I am still not getting how this is possible. Can ...
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0answers
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Finding the Nyquist Frequency of Irregularly Sampled Discrete Data

According to L. Eyer et al. (1999), the correct Nyquist frequency of irregularly sampled data is $$ \frac{1}{2p} $$ Where $p$ is the largest value such that: $$ \forall t_i,t_i = t_1 + n_ip \\ \...
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1answer
555 views

Benefits of oversampling in a realtime noise-cancellation system

When sampling a signal, it is standard practice to use a sampling rate that is greater than two times the bandwidth of the signal in order to avoid aliasing. The result is then low-pass filtered (and ...
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2answers
97 views

Nyquist Frquency isn't what it is supposed to be

I am new here and also am not very knowledgeable about DSP so this might be dumb and easy. I am aware of the fact that in order to reconstruct a signal, I need to sample it at a frequency that is more ...
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1answer
122 views

Nyquist Rate Determination

If the Nyquist rate for xa (t) is Ωs, what is the Nyquist rate for xa(2t)? Will it be the same, increase 2 folds or decrease 2 folds?
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I still get aliasing of my signal, even though I stay below the Nyquist frequency. What am I missing?

Thanks in advance for any help with my newbie question. I've been consulting quite a large number of resources in order to understand how I can create and playback a nice sawtooth without aliasing, ...
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0answers
572 views

Sampling rate: camera resolution when taking a photo of an LCD

Consider a digital camera that faces an LCD and that is perfectly focused on the LCD. The LCD shows an image of $n \times n$ pixels. What resolution does the camera have to have to perfectly capture ...
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0answers
54 views

Do we have aliasing with this chip rate and transmission bandwidth

A particular communication system I came across defines chip time to be 0.57 ns and consequently chip rate is 1760 MHz. The transmission bandwidth is 2.16 GHz. I am wondering, do we suspect to have ...
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1answer
143 views

Compressed Sensing vs Common Compression Approaches

I have a very basic question regarding common compressing approaches. Often, I have heard something like "The problem in our common way to compress data is, that we have to acquire a huge number of ...
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1answer
57 views

Cannot recreate a simple Nyquist series in Matlab

a Nyquist series should look something like {...-1, 1, -1, 1, ... }, which i think means it is a sine wave sampled at the peaks and valleys exactly. Now, given a sampling rate of 48 Hz, the Nyquist ...
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1answer
46 views

nyquist fequency

simple question, but I cant seem to understand how they got the answer. I have $x(t)$ as a signal, and I'm told that its Nyquist frequency is $\omega_0$ I'm asked - what is the Nyquist frequency of ...
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1answer
49 views

input output read/write frequency

I am trying to identify a system based on input/output response and thereby estimate a transfer function. I generated a frequency sweep function in Mathematica which gives me the discrete values of a ...
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1answer
75 views

100 kHz sinewave contaminating a signal sampled at 48 kHz

If sampling at a rate of 48 kHz, with no anti-aliasing filter on the input, and the input signal is contaminated by a 100 kHz sine, at what frequency would the sinewave signal appear in the output ...
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1answer
552 views

Why remove energy at Nyquist before ifft?

I've heard that you should remove the energy at Nyquist before performing the ifft. Why is it that you can't leave the Nyquist energy there, is there danger of aliasing somehow?
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1answer
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Sending a Filtered vs Non-Filtered speech over a Communication Link

To send a $10 \, KHz$ bandwidth of speech (Non Filtered speech), Nyquist criteria says that sampling duration should be $50 \, \mu s$. While for a $4 \, KHz$ bandwidth of filtered speech, sampling ...
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1answer
212 views

Nyquist Criterion in higher dimensions

I was just wondering if there were any "obvious" resources, papers, or textbooks I should look into regarding the nyquist-criterion in higher dimensions. For example, this would be relevant if there ...
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1answer
773 views

What is the minimum sampling duration to capture a given frequency?

Due to the Nyquist rate, you need to sample twice as fast as the highest frequency you want to measure. Then when you do a FFT the number of samples determines the number of bins and thus the ...
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1answer
114 views

Processing 47-53 MHz signal sampled at 96000 Hz

I am fairly new to the topic of DSP and FFT and I have hit a mental block. For a project, I am trying to pick out frequency's with amplitude peaks in a 47-53 MHz signal. This signal is being put ...