Questions tagged [aliasing]

In signal processing and related disciplines, aliasing refers to an effect that causes different signals to become indistinguishable (or aliases of one another) when sampled.

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PolyBLEP: solving two part residual

The Polynomial Bandlimited Step (PolyBLEP) methodology involves approximating the sinc() function with a polynomial. The most basic polynomial to choose is a uni-polar triangular pulse as it is the ...
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25 views

Problem Involving Aliasing and Critical Fusion Frequency Concepts

I have been trying to study a course from MIT on Biomedical Signal Processing and I thought that the best way to learn would be to solve some problems. Although they might be out of my depth, I am not ...
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Apply timeshift to undersampled signal after bandpass after sampling?

I have sampled my continuous signal $x(t)$ at $x[n]=x(n/f_{\rm samp})$. The signal is undersampled, and I know I will not be able to recover my original signal anymore. After sampling a bandpass is ...
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37 views

Why should wavelet re-synthesis produce an output when the main component is suppressed and what does this mean for denoising?

I understand that aliasing occurs in DWPT if the wavelet used is of low order since the "filters" are not perfect and the combination of down sampling and overlapping between bands causes ...
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30 views

synchronize adcs with neuronal network

if i have two adcs(analog to digital converters) sampling a signal. Is it possible to synchronize the two adcs with deep learning? as far as i know, with super-resolution on image processing it is the ...
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31 views

Partially aliasing in Signals

I have read a paper about super resolution where signals are used that are partially aliased. here the paper If the sampling rate is smaller than the 2*max frequency but greater the max frequency, ...
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55 views

Aliased Signal's Frequency

So I have an incoming signal of 137.9 MHz and a sampling frequency of 1.4 MHz. Once sampled how do I calculate the aliased ...
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254 views

Aliasing from downsampling and Nyquist

In a book Conceptual Wavelets in Digital Signal Processing by Lee Fugal 2009 on page 246 the author talks about aliasing present in DWT subbands due to downsampling by 2 and states: Recall from DSP ...
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261 views

Decimation Aliasing

Lets say you have a signal which is sampled at rate $f_s$ and the bandwidth after sampling is $B$. Now you want to decimate this signal with a new sample rate $f_{s, new}$ where $f_{s, new} < f_s$ ...
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95 views

Band Limited Impulse Train - DC offset correction

I am trying to get band limited saw-tooth wave. I have found this paper: Alias-Free Digital Synthesis of Classic Analog Waveforms. I am prototyping this code in common LISP, here is snippet of what I ...
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134 views

Can picking an inappropriate roll-off frequency for a digital filter just alias the roll-off value?

I believe a related question is asked here, but my question deals more with what filter is realized if one fails to consider design parameters relative to sampling rate. In designing an IIR filter we ...
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159 views

How to Sample Smooth Random Walks of Instantaneous Frequency

I want to generate a random sequence for instantaneous frequency with as little aliasing as possible (i.e I expect to see as close to constant amplitude as possible, with only the frequency varying). ...
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55 views

Every second sample noisy

I sampled a signal and unfortunately every second sample is very noisy. The noise is Gaussian and bandlimited exactly in the same bandwidth as my signal. Is there a way to improve the noise without ...
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380 views

Can sample aliasing of strictly white noise lead to random walk (drift) in the sampled signal?

Aliasing of tones higher than the Nyquist frequency, and where the tone may have some degree of nonlinear distortion can appear as low frequency 'drift' or even near static bias in the sampled signal. ...
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What should be my sampling frequency for a peak detector output where it is extremely important for me to capture the first time the peak occured?

Following is the output of the peak detector: The amplitude is not important to me, however the time when the peak occurs is extremely important. So my microcontroller will have an algorithm like ...
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156 views

Band limited discrete signals division

If I take two analog, band limited signals $ x(t) $ and $ y(t) $ with non-zero $y(t)$ I can define the division: $$ z(t) = \frac{x(t)}{y(t)} $$ In general $z(t)$ may have a very wide bandwidth, also ...
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35 views

How to prevent (or remove) aliasing when a cross-correlation between spectra is performed

This is my problem: I'm implementing a tool which cross-correlates a spectrum (fluxes as function of wavelength, obtained directly from an instrument) with a template (fluxes as function of wavelength,...
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30 views

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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87 views

Direct Digital Frequency Synthesis, NCO and negative frequencies

I need to translate a frequency band generated by a DDFS designed in a FPGA (using Xilinx DDS Compiler). My output to the NCO is in I/Q format. I chose to use a NCO to perform the frequency shift but ...
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430 views

IQ Sampling and Oversampling Differences? *Confused*

Two different thought process that produce two different alias band calculations .... What concepts are these? If I have two 1 GHz ADC's and they sample with 90 degree offset (A comment said this is ...
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81 views

Minimum sample frequency that allows reconstruction of information signal but VIOLATES Nyquist?

Say in the frequency spectrum, you have an information signal between (-100, 100) Hz, and a noise signal between (-700, -500) and between (500, 700) Hz. What is the minimum possible sample frequency ...
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131 views

Sample-rate, filtering, digital-filtering and aliasing

I am strugling with a question that I hope someone can help me with. I am recording single molecule events which I detect is picoampere square deflections. I wish to use as gentle low-pass bessel ...
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122 views

What does the frequency band mean when it comes to finding aliases?

The time signal which i'm trying to find the aliases for is: $$x:{\mathbb R}\rightarrow {\mathbb R}\\\ x(t)=\cos(50t) +2\cos(70t).$$ If the sample period is $T_s = \frac{\pi}{60}$ then according ...
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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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116 views

Exact formula for alias of Discrete Fourier transform for periodic sigals

Suppose that $f(t): \mathbb{R} \to \mathbb{C}$ is a $T$-periodic signal, with highest frequency $f_h$. Now suppose that our sampling rate frequency is lower than $f_h$, and is not any multiples of $1/...
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344 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 ...