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poster · 2019-11-25, 18:21

I have a signal which is a linear combination of two frequencies and I am trying to use MATLAB to determine what frequencies the (main) signal consists of. As an input I have the sample rate, rate and a row vector with the signal data, segment.

Now I have the following code:

N=length(segment);



freq = rate*(0:N/2)/N;

X = fft(segment);

X=X(1:N/2+1);



plot(freq*2, abs(X))

And this indeed returns a graph with two peaks, one at each of the frequencies the signal consists of. Now I want to extract these frequencies. So I want to return a variable, signal, which is a vector of the two frequencies.

Hence, if my signal is created by the linear combination of a signal of 30 Hz and one of 60 Hz, then I want signal = [30,60]. I can create a graph and then identify this, but I want to cut out that middle man and just return the found frequencies, without using any toolboxes.

How can I find my desired frequencies?

2019-11-25, 18:21	#1
poster 高级会员注册日期: 2019-11-21 帖子: 3,006 声望力: 66	Using fft to extract frequency I have a signal which is a linear combination of two frequencies and I am trying to use MATLAB to determine what frequencies the (main) signal consists of. As an input I have the sample rate, `rate` and a row vector with the signal data, `segment`. Now I have the following code: `N=length(segment); freq = rate(0:N/2)/N; X = fft(segment); X=X(1:N/2+1); plot(freq2, abs(X))` And this indeed returns a graph with two peaks, one at each of the frequencies the signal consists of. Now I want to extract these frequencies. So I want to return a variable, `signal`, which is a vector of the two frequencies. Hence, if my signal is created by the linear combination of a signal of `30 Hz` and one of `60 Hz`, then I want `signal = [30,60]`. I can create a graph and then identify this, but I want to cut out that middle man and just return the found frequencies, without using any toolboxes. How can I find my desired frequencies? More answer...