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# 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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### Aliasing in Doppler Radar

my book about RADAR says that: If a Continuous wave radar sends a sine wave at frequency $f_T$ to a moving object (at speed V), a frequency $f_R$ is received. Their difference is called Doppler ...
1answer
44 views

### Digital lowpass filter causing aliasing

I'm writing a biquad filter program in C++, using the LBJ Cookbook as the source for the formulas. https://webaudio.github.io/Audio-EQ-Cookbook/audio-eq-cookbook.html The lowpass filter that I've made ...
1answer
37 views

1answer
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### Can the (point-wise) multiplication of two discrete band-limited functions be inherently aliased?

I'm not fully used to the language of DSP, so forgive me if I confuse some of the notation, or if the below is trivial. I'm interested in the case where we want to do the point-wise multiplication ...
2answers
243 views

### What is the right way to downsample using Fourier method?

I want to know what is the right way to downsample a sampled signal using Fourier transform as the implementation in scipy.signal.resample confuses me. Reading ...
3answers
272 views

### Digital to analog aliasing or mirror query… DAC can output negative frequency?

Using a clock Fs = 1 MHz. The Digital to Analog (DAC) can make frequencies upto 500 KHz. 500 kHz to 1 MHz is an alias? Or is it called a mirror?? Is aliasing a concept only on the ADC and sampling ...
0answers
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 ...
2answers
518 views

### Where should I set my anti-aliasing filter corner frequency for this signal?

I have a Fourier transform of an arbitrary digital signal. The transform has For 1024 frequency bins. The magnitude plot of the first 100 is below, with no surprises in the unplotted 924 bins. Now, ...
1answer
99 views

### Values of angular frequency of discrete-time sinusoidal signal

Why are the values of angular frequency of discrete-time sinusoidal signals in between -pi and pi?
1answer
459 views

### How to prevent distortion after down-sampling?

I am new to audio signal processing, but in one of my machine learning projects that I am working on, I need to down-sample my audio somewhere in the middle of my neural network. Therefore, I need a ...
1answer
70 views

### Why does my sinusoid look “AM” in shape?

My code is : Fs=200e6; Ts=1/Fs; NFFT=2^14; Runtime=(NFFT-1)*Ts; t=0:Ts:Runtime; f_in=90*1e6; y_in=sin(2*pi *f_in *t); plot(t,y_in) ylim([-1.5 1.5]) Then why does ...
1answer
40 views

### Aliasing correspondance with respect to DFT

Given a sampling frequency Fs lets say we plot the magnitude of the fft of a temporal signal $x$, for different frequencies above the Nyquist frequency, to show the effect of aliasing: ...
1answer
205 views

### Better understanding of downsampling (decimation) and upsampling (interpolation)

Although some questions were asked about this topic, I have not seen any that answers all the basic questions, that is why I took the liberty to ask more about this. I suggest to limit, (or at lest ...
2answers
99 views

### Is spectral leakage normal for FFT?

I record a sample of 2000 data points, with a sampling rate of 40khz, so freq. resolution is 20hz. I multiplied the chunk of data with a Hanning window prior to doing the FFT. I recorded a 1khz test ...