# 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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### 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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### 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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### Sampling and Aliasing

What is meant to be explained in the section between the 2nd paragraph and the folding section in the Sampling sinusoidal functions section shown in this link? Why is $Nf_0$ written in $f+Nf_0$ ...
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### Why I don't have phenomena of aliasing after resize image in frequency domain?

I'm writing code in cuda/c++ languages to resize images. I used a box filter ( it response in spatial domain is sinc filter ) and I have applied the convolution theorem and I'm using the fourier ...
1 vote
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### Removing aliasing from recorded signal

I am recording a signal from a vibration sensor with a frequency response that stops at about 7kHz, but linear up to 1kHz. I am thus recording data from it using an Arduino at 2kHz, so that signals up ...
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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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### How to visualize frequency domain of signal with multiples of $f_s$?

Is it possible to visualize signal in frequency domain for frequencies bigger than $f_s$? I'd like to get the plot of some example signal like that: I tried to create some signals in ...
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### Noise from irregular sampling pattern

In this paper the author says By using an irregular sampling pattern and filtering the irregular samples to create the pixels, featureless noise is produced from such high frequencies rather than ...
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### Sampling pure tone sine waves [closed]

What would happen if I am using the maximum frequency as the sample rate for sampling a pure tone sine wave? For example, a $10\ \rm kHz$ sampling frequency for a $10\ \rm kHz$ monotone sine wave. ...
1 vote
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### Difference in information between IQ Sampling vs. Real Sampling at $2F_s$

As per my current understanding we use IQ sampling as way to increase the useful bandwidth to Fs rather than $F_s/2$ when viewing the FFT because the IQ sampling removes the negative frequencies and ...
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### 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 ...
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### Aliasing at $f_0 + kf_s$

In this question, it has been proved that $x(t) = \sin(2\pi f_0 t)$ and $x_k(t) = \sin(2\pi (f_0 + k f_s) t)$ have the same sample points. So sinusoids with frequencies $f_0$ and $f_0 + kf_s$ will ...
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### Generating digitized white noise: uniform vs normal sampling

Consider the following two ways of generating noise in the time domain for audio applications: Generate samples from a uniform distribution [-amplitude, +amplitude]...
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### Sampling a low-frequency sound doesn't work at some sampling rates

When sampling a low-frequency sound (like a 55Hz sine wave) I hear an additional high frequency sound at certain sampling rates, but not at others. This happens in Audacity and in my own program. For ...
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### Sine Wave "Lobes" (Basics, and probably a dumb question)

I am beginning my journey on trying to understand a little deeper on signal processing. I wonder if the effect I am seeing is worth any spit or is there a deeper level of understanding is apparent I ...
1 vote
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### 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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### 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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### aliasing in image processing

I know that aliasing occurs when a signal is subsampled. If the sampling rate is lower than twice the max frequency in a signal, aliasing occurs. How is it in pictures? as far as I know, a sinc-filter ...
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1 vote
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### Decimation Question about using a low pass filter before downsampling

I have a bunch of audio files that have a sample rate of 380kHz, however I would like to reduce this sampling rate to 44.1kHz. From doing some research online, it seems like I will have to use a low ...
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1 vote
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### 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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### 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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### 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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### What is an example of using aliasing to your advantage when recovering an input signal?

Suppose you have an arbitrary analog input signal $x_a(t)$ guaranteed to have frequencies within a bandwidth $[f_1,f_2]$ Hz. Suppose your sampling frequency $F_s$Hz, and sample $x_a(t)$ to produce \$...
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### Multichannel sampling with aliasing

if i have 2 sensors, sensor1 and sensor2, that sample a signal on complementary points so that sensor2 samples always between sensor1s sampling points. can I achieve the doubled sampling rate with the ...
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### Loosing information in decimation - without aliasing

We sample each other sample (01010101). Now say we have a signal - that is inside the original sample which has the pattern of (010-1). Decimation gives us 000 for this sub-signal. How to prove this ...
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### How do you sub-sample an FFT?

I'm currently trying to understand this paper on a Sparse Fourier Transform. On page four, there is a section on a sub-sampled FFT. The purpose of this section is to show that you can compute a sub-...
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### Measuring Phase Difference at DC bin aliased frequency using FFT

I have a code in which two complex signals (I/Q) are created having same frequency but with phase difference. FFT of both signals is taken and atan2 is used to compute phase after which the difference ...
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### aliasing folding phenomena in frequency domain matlab

Hello i am trying to create the folding phenomena of undersampling in matlab, When i undersample the sampling frequency is 135 less than the Nyquist frequency for 70 Hz signal ou will see that it is ...
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### How do Anti-Aliasing Filters filter the signal?

I have programmed a anti-aliasing filter that uses the fourier-transformation and makes a perfect cutoff on my desired cutoff frequency for downsampling without aliasing. I have read about other ...
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### Super resolution with aliased signal

SKIP to Questions below if you want : In super resolution I can create a high resolution signal from a low resolution signal. But it is also possible that the low resolution signal contains aliasing. ...
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### How to find correlation between two signals regarding peaks?

In a super-resolution task, I try to predict the higher frequencies of a signal. X low-resolution (lr) is my input and Y high-resolution (hr) is the target. Where X contains only frequencies till 2 ...
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