Signal Processing Stack Exchange
Signal Processing Stack Exchange

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1500 questions
7
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3 answers

Decreasing Sample Rate in DFT (FFT) for Audio Analysis

I'm working with audio data analysis through FFT algorithm. My example audio is a sine wave at 440 Hz and 44100 Hz sampling rate. FFT methods in programming, like scipy.fft(y), require a vector of samples and a number of points/samples to…
mortalis
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Why Is Non Linear Least Squares Method from MATLAB and Alglib Gives Different Results on the Same Data?

i'm trying to rewrite my Matalab prototype for some DSP to C++ and encountering a displeasing problem. I'm trying to fit data to a function $y = a * (\pi / 2 + arctg(b * x))$. In Matlab it works well with the following code: fo =…
user35839
7
votes
3 answers

Neural Networks and Complex Valued Inputs

[not sure if this or stats.stackexchange was the correct location for this post, so put it on both for now.] I've seen some recent papers describing complex valued neural networks like this one: Deep Complex Networks, 2017, Trabelsi et al.. What I'm…
Austin
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Choice of Gaussian kernel parameters when lowpass filtering before image resampling?

I need to decimate a signal by a factor of q. More specifically my signal is a 3D "image": $\ I(x_i,y_j,z_k)$, which I need to downsample by a factor of two in the z direction. I want to do lowpass filtering before decimation by convolving with a…
Andy
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1 answer

Gradient of Total Variation of Magnitude of Complex Function for Denoising

Say I have a complex function $f^*$ (e.g. a MRI image) that has a near piece-wise constant magnitude, but a non constant phase. If I have an optimization problem to find $f^*$ and set up an objective function with a total variation term (e.g. for…
Stiefel
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1 answer

What is the bandwidth of product of two signals?

For signal $x(t)$ with bandwidth $B_x$ and signal $y(t)$ with bandwidth $B_y$, what will the bandwidth of the signal $z(t)=x(t)y(t)$ be?
j.e.rogers
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7
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3 answers

How detect signal from noise?

I'm trying to detect when a signal is "on" from samples I have. Those samples come from a software defined radio, if that matters, and the signal i'm trying to detect is a WiFi signal. The problem is separating "noise" from "signal", as I did by…
user35067
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5 answers

Curve Fit of Step Function with Boundary on the 2nd Derivative

Consider this step function: The signal that "fits" this should look like the following (in green): The corners are now smooth because the maximum second derivative allowed is not infinite anymore. The idea is to find the most close to the…
Juan Molina Riddell
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7
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2 answers

Vanishing Moments

I am reading a book titled "Two Dimensional Wavelets and their relatives" by Antoine et al. and it talks about vanishing moments. I have trouble understanding the exact significance of it. Can anybody give an idea on vanishing moments?
mkuse
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7
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1 answer

Can addition of two band limited signals create aliasing?

Can mixing/adding two band-limited signals create any frequencies above Nyquist?
user17127
7
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1 answer

Remove Shadows from Contour of an Object (Grapes)

I want to extract only the grapes from the images. Unfortunately, sometimes I don't get the grapes exactly. I have a code that doesn't work well in all cases. Sometimes, it does not differentiate between the shadows and the grapes. The example input…
Alon Shmiel
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7
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4 answers

Reducing noise from the same frequency band as signal

Sorry for the vague question (as I'm not even quite sure what I want to do is possible), just asking for some general direction to take my research. For a brief description, my signal resembles exponentially distributed noise, bandlimited, with a…
LDPC
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7
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3 answers

Need a better step detection algorithm

I have a time series with lots of steps/jumps (data file here). A plot is given below. I would like to subtract an appropriate value for each of these square wave features to bring them back down to the baseline of the signal. A median filter works…
vibe
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how does this equation correspond to smoothing?

Please help me understand smoothing of data. This is a follow up to my previous question posted here. Especially the top answer by Junuxx where he says a way of smoothing a function $f(x)$ is: $$ f'[t] = 0.1 f[t-1] + 0.8 f[t] + 0.1 f[t+1] $$ here we…
user13267
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7
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1 answer

FIR filter gain

I'm writing a C function to generate bandpass FIR filter coefficients using a simple window method (more details here FIR filters by windowing) The important code snippet is the following (f1 and f2 are the low and high bandpass frequency, fs is the…
Yozek
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