Neural network input/output problem, signal estimation

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Michal Taraaram
Michal Taraaram 2016-5-13
回答： Staffan 2016-5-14
Hello everyone.
I'm new in NN stuff and I've got a problem.
I want to project a neural network which can estimate amplitudes and frequencies of periodic signal with additional noise. This signal is a sum of 2-4 sine waves (+noise). I tried to solve it in several ways but nothing works. Maybe can you give me any advice, what should I give to input, and what kind of array/matrix I need to put on target output? What kind of network should it be? I tried to put on output every single A*sin(2*pi*f*t) but on training data - that works, on testing data - definitely no.
I will be so grateful for every advice! Hope you can help me! :) Thank you.

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回答（2 个）

Greg Heath
Greg Heath 2016-5-14
Neural Nets are not appropriate for that type of task. See
help fft
doc fft
Hope this helps.
Thank you for formally accepting my answer
Greg
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Michal Taraaram
Michal Taraaram 2016-5-14
But theoretically if I have real amplitudes (A1, A2, A3) and frequencies (f1, f2, f3) from signal without noise, is there a possibility to project neural net that on input have a matrix with few rows containing few samples of signal with noise, and on target there will be some kind of array containing those amplitudes and frequencies?

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Staffan
Staffan 2016-5-14
Hello Michal,
Could this solve your issue?
http://se.mathworks.com/matlabcentral/answers/121579-curve-fitting-to-a-sinusoidal-function
I just used the code in the accepted answer to fit a sine function. Since the original data (simplenar_dataset, may be used e.g. when working with narnet) had a rather sparse sampling rate I added a third vector to the figure in which I decreased the between the points with two orders of magnitude. If you would like to do the same, just replace the plot command with this line:
plot(x,y,'b', xp,fit(s,xp), 'r', min(xp):0.01:max(xp),fit(s,min(xp):0.01:max(xp)),'g')
Regards
Staffan

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