How to separate signals with diffrent frequencies

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Srey 2015-1-1

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评论： aarthi arunachalam 2016-3-11

t = linspace(0, 1, 1001);

x=sin(2*pi*t*3) + sin(2*pi*t*6) + sin(2*pi*t*10)+sin(2*pi*t*13)+sin(2*pi*t*20)+sin(2*pi*t*50)+sin(2*pi*t*100)+sin(2*pi*t*200);

% my signal with frequencies 3,6,10,13,20,50,100,200 KHz

sigma=0.1;

y=x+randn(size(x)).*sigma; % adding noise

I filtered the signal using fft.

I want to separate signals.

Eg : from my original signal, I want a signal with frequency range say 3 to 8 KHz, another signal say from 100 to 200 KHz. How can I separate them and display those signals.How can I do this. Anybody Please help me to solve this.?

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mouh nyquist 2015-1-1

you must read about chebishev and butter filter

aarthi arunachalam 2016-3-11

i too want to seperate certain frequency range from my original signal. can you help me?

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Answer 1

Shoaibur Rahman 2015-1-1

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Add the following lines of code at the bottom of your code (after y=x+randn(size(x)).*sigma;):

ffty = fft(y);
ffty = abs(ffty(1:ceil(length(y)/2)));
ffty(ffty<100)=0;
[~,locs] = findpeaks(ffty);
freqs = (locs-1)/t(end)
signal_1 = sin(2*pi*t*freqs(1))+sin(2*pi*t*freqs(2))+sin(2*pi*t*freqs(3)); % 3-10
signal_2 = sin(2*pi*t*freqs(6))+sin(2*pi*t*freqs(7)); % 50-100
subplot(211), plot(t,signal_1)
subplot(212), plot(t,signal_2)

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Srey 2015-1-1

编辑：Srey 2015-1-1

在 MATLAB Online 中打开

In above code, the range is set based on the values obtained in freqs. If the signal is x1 =

Now i want to separate those frequency ranges, from this signal.I am getting, freqs =

   Empty matrix: 1-by-0
Also, ,ffty(ffty<100)=0; ,why giving 100?

Shoaibur Rahman 2015-1-1

编辑：Shoaibur Rahman 2015-1-1

在 MATLAB Online 中打开

Use any sinusoidal function to generate a signal with that frequency, and then plot that against time. For example:

t = .....
out1 = sin(2*pi*f1*t);
out2 = cos(2*pi*f2*t);
etc....

This is just from the Fourier analysis, that states any signal (with some criteria) can be represented as summation of infinite sinusoidal functions. So, to represent only one frequency, use one sinusoidal function, or to represent multiple frequency components, use summation of multiple sinusoidal functions with those frequencies.

Srey 2015-1-1

Thank you so much..It works.:)

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Answer 2

Pourya Alinezhad 2015-1-1

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https://ww2.mathworks.cn/matlabcentral/answers/168641-how-to-separate-signals-with-diffrent-frequencies#answer_163764

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1-you can use several filters with different center frequencies (chebishev or butter filter)

h  = fdesign.bandpass('N,F3dB1,F3dB2', N, Fc1, Fc2, Fs);
Hd = design(h, 'butter');
filter (Hd,input_signal);

2- you can use an adaptive filter and feed the signal and the desired signals to it (LMS filter).

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Srey 2015-1-1

I want a signal with freq range:say 3-10Hz and another signal with freq say 50-100. I want to plot them separately.How can be done from my original signal

Pourya Alinezhad 2015-1-1