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the spectrum of a message is shown as follows
where magnitude plot of the Fourier transform for message versus frequency in Hz is seen.
how can i find the dominant frequency with the use of the command max and command freqz?
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Why are you calling freqz() on the frequency response???
[freq_resp,freq]=freqz(message,1,100000,22000); [maxval,index] = max(abs(freq_resp)); freq(index)
I also question whether you should be using freqz(), That is really intended for filters where the inputs are the filter numerator and denominator coefficients.
Why not use the PSD
[Pxx,Fxx] = periodogram(message,rectwin(length(message)),length(message),22000); [maxval,index] = max(Pxx); Fxx(index)
If you are using freqz(), freqz() returns the frequency vector, so just query the max value of the absolute value of the frequency response and then use that index to find the frequency.
h = [1/sqrt(2) 1/sqrt(2)]; [H,F] = freqz(h,1); [maxval,index] = max(abs(H)); F(index)
This example gives 0, because h is a lowpass filter with the maximum at 0 radians/sample.
freqz() takes the sampling frequency as an input argument so that you can get the frequencies in Hz.