Signal Processing Stack Exchange
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1500 questions
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3 answers

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 series (say 4) of still pictures using a…
Lord Loh.
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Finding zebra-like pattern in image (Detection of structured-light fringe centerline from photo)

I'm working in a project where fringes are projected against a subject, and a photo is taken. The task is to find the centerlines of the fringes, which represent, mathematically, the 3D curve of intersection between the fringe plane and the subject…
heltonbiker
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Discrete-time Fourier Transform of the unit step sequence $u[n]$

From text books we know that the DTFT of $u[n]$ is given by $$U(\omega)=\pi\delta(\omega)+\frac{1}{1-e^{-j\omega}},\qquad -\pi\le\omega <\pi\tag{1}$$ However, I haven't seen a DSP textbook that at least pretends to give a more or less sound…
Matt L.
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Why do we need to conjugate complex signals in autocorrelation and cross correlation

Why is it necessary to conjugate $f(t)$ while performing auto correlation or cross correlation with respect to $g(t)$, if $f(t)$ and $g(t)$ are complex signals?
Vinayak Killedar
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2 answers

When does the laugh track kick in?

One of my weekend projects has brought me into the deep waters of signal processing. As with all my code projects that require some heavy-duty math, I'm more than happy to tinker my way to a solution despite a lack of theoretical grounding, but in…
Erik
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14
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3 answers

Why do SDR receivers emit I/Q samples?

To my understanding hardware receivers for software-defined radio applications basically take the input signal, mix it with the tuning frequency to remove the carrier frequency and then sample the resulting voltage with a sampling rate that is just…
AndreKR
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When are two signals orthogonal?

The classical definition of orthogonality in linear algebra is that two vectors are orthogonal, if their inner product is zero. I thought this definition might be applied to signals as well, but then I thought about the following example: Consider a…
user26311
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Can you increase frequency resolution of FFT without increasing window size?

I'd like to use STFT for multipitch analysis. I realise detecting the partials existing in the signal is just the beginning. Still I have problem with it. Let's say I have signal sampled with 'CD' frequency 44100Hz. With window of 1024 samples I…
nuoritoveri
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Is there any alternative characterization of sparsity of a signal in compressed sensing

The starting assumption for compressed sensing (CS) is that the underlying signal is sparse in some basis, e.g., there are a maximum of non-zero Fourier-coefficients for an $s$-sparse signal. And real life experiences do show that the signals…
Arnab
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Why is circular convolution used in DSP? Why not linear convolution?

Why are we using circular convolution in DSP? What's the main solid reason for the use of it in digital processing? Why does the concept of circular convolution come more often than linear convolution?
vishaln
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Which kind of machine learning algorithm is Hidden Markov Model?

I have used Hidden Markov Model algorithm for automated speech recognition in a signal processing class. Now going through Machine learning literature i see that algorithms are classified as "Classification" , "Clustering" or "Regression". Which…
user1411110
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How to detect edges and rectangles

I try to detect rectangles in images. The background of the images is one color (most of the time). I tried two methods to get an binary image (1 = background, 0 = edges), to do an Hough Transformation later on... Sobel or Canny Filter Smooth image…
patr
14
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4 answers

Intuition for sidelobes in FFT

I was wondering if there's a intuitive way to understand why sidelobes appear when performing an FFT on a signal of fixed length?
CatsLoveJazz
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How to make frequency axis for even and odd FFT length?

Can I get help on how to make frequency axis going from negative frequency to positive frequency, (in Hertz), that will be the x-axis in an FFT result, but given either an even length FFT, or odd length FFT. I am having some troubles making it in…
TheGrapeBeyond
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Why do linear systems show sinusoidal fidelity?

I am looking for a proof for sinusoidal fidelity. In DSP we study a lot about linear systems. Linear systems are homogenous and additive. One more condition it satisifies is that if a signal is a sine or cos wave then the output only changes the…
Hobyist
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