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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how to correct minBLEP sawtooth oscillator DC bias

In my implementation of minBLEP, overlapping minBLEPs result in a DC bias as the frequency increases. This is because each minBLEP correction (i.e. the minBLEP minus the aliased step) has a DC bias. ...
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27 views

What does it mean for a signal to alias to another?

I know the definition of this is simple and I do understand the concept of aliasing (I think) in the way that multiple signals can be aliases of each other. For example, I get it when some one says: ...
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51 views

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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1answer
55 views

Sampling of band-limited white noise

The context is communication where we have a front-end that samples a signal and a noise (but here we focus only on the noise). My goal is to determine the noise power that I should use to simulate ...
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1answer
36 views

Can aliasing happen in Laplacian Pyramids?

I want to use the Laplacian pyramid framework for representing images. The The Laplacian Pyramid as a Compact Image Code's language seems to provide freedom in the choice of blurring/interpolation ...
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3answers
125 views

Reflecting negative frequency to positive frequency

I am trying to synthesize sinusoids by using window function in the frequency domain. It involves: In frequency domain, shift the window to center around the peak frequency To generate a DFT ...
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1answer
38 views

Aliasing of a Signal

I am really confused about this exam question regarding Aliasing. I have a signal of 2Hz, which I needed to draw a square wave of, over a period of 8 seconds. It Then asks, "Starting from the ...
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0answers
60 views

calculating FFT of signal with additional zeros

I have a problem where by I calculate the FFT of a signal $x$ (an image to be exact) after zero padding it: X=fft([x zeros(n)]) where $zeros(n)$ is just the ...
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1answer
36 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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23 views

Does MSAA make sense in audio / 1d data streams?

In graphics, MSAA is a technique where you take multiple samples of something per pixel and then average the values to get the final pixel value. The image quality improves as a result, and its ...
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47 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 ...
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183 views

aliasing to a 50 Hz sine wave sampled at 5000 Hz sampling rate?

I sampled a 50Hz sine wave (its not perfectly a sine wave, it's a data coming from current sensor using Arduino). Using real time graphing technique by sending the data from Arduino to the PC I ...
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52 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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1answer
40 views

How does sampling and subsequent resampling affect aliased harmonics?

If I sample a signal with a harmonic higher than half my sample frequency I can predict the aliased frequency easily as $$|F_h-kF_s|$$ But what if after sampling the signal, I re-sample at a lower ...
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2answers
67 views

What is the proof of the equation for the aliased frequency fa = |R*n - fs|?

R (sampling rate) fs (signal being sampled fN (the Nyquist frequency) fa (aliased frequency) I was hoping someone could explain to me why this is true with a more mathematical proof. it seems ...
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3answers
95 views

Soft question: Why do we need to reconstruct a signal?

I am currently reviewing the Nyquist criterion which says I need to sample the signal at 2 times the maximum frequency in order to avoid aliasing in the reconstructed signal. My question is that in ...
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0answers
56 views

Illustration of timed domain aliasing cancellation (TDAC, MDCT, lapped transform)

Can someone find or make a visual illustration of how time domain aliasing cancellation works in lapped transforms such as the MDCT? I think a graphic would make it a lot easier to understand, and I ...
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1answer
145 views

How can I enforce aliasing with Audacity?

I would like to hear how aliasing sounds like. How can I get this with Audacity? (I was told that I should adjust the Fourier coefficients in Audacity. I have no idea where I can do so / how I should ...
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1answer
100 views

why Sampling with higher than nyquist frequency is causing aliasing?

fm=20000 and I am sampling following signal at 65000 Hz: ...
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1answer
173 views

How does the number of frequency-domain sampling points influence the outcome of an inverse FFT?

Given some frequency-domain representation of an impulse response. How does the number of frequency-domain sampling points influence the outcome of an inverse FFT, if I keep the sampling frequency ...
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1answer
82 views

Designing the filtering for a time domain data acquisition application

I want to filter sensor signals for a data acquisition application on an ATmega microcontroller. The interesting parts of the signal are in the range 0-5Hz, and I'd like to leave these mostly ...
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3answers
345 views

Visualizing aliasing in Matlab

I am trying to verify for myself that aliasing actually makes it impossible to distinguish the "real" and the aliased frequency. What I have done it set the sampling rate to 20 Hz and created two sine ...
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1answer
60 views

What does “two signals aliasing to each other” mean?

So I just read something that two signals are aliasing to each other. I know what a single signal is being aliased - that is when sampling rate is not higher than or equal to the Nyquist rate. But I ...
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165 views

Spectral images - How do they appear during ADC?

Why is it that spectral images appear? I know they appear for $F_s$, but why those replicas appear, I don't know. E.g., sampling $x(t) = sin(1000 * 2\pi t)$ with a sample frequency of 230 Hz. I know ...
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2answers
88 views

Generating a sound where end frequency is 1/2 of the start frequency

I am very very new to signals, and I am trying to generate sounds based on some parameters from a database. So, the database stores the following: startFrequency endFrequency startAmplitude ...
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1answer
96 views

Which antialiasing filter before equispaced sampling

I am using MIT-BIH arrhythmical database where I have a digital signal of 1200 Hz so 1200 samples per second. This means that analog filters have already applied to remove the frequencies over Nyquist ...
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76 views

Create an aliased image in FD

Is there an accurate way to create an aliased image from the Fourier transform of the original image? in other words, i have the Fourier coefficients of an image and i want to make down-sample in ...
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1answer
191 views

Simple analog anti aliasing filter good enough if signal frequency is far from sampling frequency ? What about equivalent time sampling?

I have one and only one frequency signal, a sine signal at f = 10 kHz that is sampled at Fs = 320 kHz. I have read about applying a simple analog anti aliasing (AAA) filter then oversample, do some ...
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3answers
995 views

Aliasing beating frequency

As I understand aliasing is because you sample a high frequency with a low sample rate, and the sample points don't have enough information about the high frequency component. Here is an example of ...
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1answer
414 views

FFT and aliasing

I have got a txt file which contains voltage and time data. When I did fourier transform using fft function in matlab I got complex numbers. I understand that the real part is the magnitude and the ...
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2answers
846 views

How to predict the spectrum of an aliased/folded signal without looking at the FFT?

This seems like a trivial concept but I just can't get the hold of it. I have a signal with two complex sinusoids having frequencies -25MHz and 17MHz. Currently it is being sampled at 64MHz so I get ...
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1answer
121 views

reduce harmonics produced by microcontroller

I'm generating an 18kHz sine signal using a dsPIC microcontroller at 44100kHz (I'm not sure I can call it sampling rate, maybe generation rate, although the concept is the same). The dsPIC's DAC then ...
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205 views

Increasing image resolution

I know of some oscilloscopes (DSA8300) that repeatedly sample at a few hundred kS/s to reconstruct a few GHz signal. I was wondering if this could be extended to 2D signals (photographs). Can I take a ...
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1answer
322 views

Using Spectrogram to check whether aliasing will occur

I was wondering if the spectrogram can be used as a MATLAB tool to check whether or not aliasing will occur when the signal is downsampled from let's say, 44.1kHz to 8kHz? And if yes, how do I go ...
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636 views

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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3answers
4k views

Alias frequency Formula

I'm taking a multimedia systems class in my MSc Computer Science, and I'm having some trouble understanding the formula for the alias frequency - this could stem from my misunderstanding of the alias ...
5
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3answers
5k views

Demonstrating the effect of aliasing

How does the signal look when we don't use the Nyquist rate to remove aliasing from a signal during sampling? Let's suppose the signal is sinusoidal, with a frequency of 500 Hz and an amplitude ...
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234 views

What is the antialiasing algorithm employed by video cards?

What is the algorithm employed by video cards when one talks about for example 8xAA? I thought the algorithm was about looking at neighboring pixels for correction. ...
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535 views

What is the effect of aliasing on the magnitude of the autocorrelation?

I've a question about the effect of aliasing on the magnitude of autocorrelations. From a simulation in MATLAB, I don't see any effect of aliasing or any need to anti-alias filter when I take the ...