I was trying to decompose an EMG signal, which was sampled at 200 Hz, into 7 levels of decomposition using DWT. And the result is shown in the figure( only up to level 3 is shown here) However, I would like to know, how to see in MATLAB that with each level, the frequency is split into high and low. How to find the power spectrum of the same(if it's possible)? So I have used this code to find out the power spectrum of level 1 detail coefficients, so the sampling rate is 200 Hz, so the highest frequency can be assumed to be 100 Hz, after one level of decomposition the d1 coefficients should be in the range of 50 to 100 Hz (correct me if I am wrong). But the problem here I am facing is that in the power spectrum it is showing power in the range of 0 to 100 Hz almost equally , I was expecting more power around 50 to 100 hz instead (Fig is inserted below). I want to understand why is it so. Also How to find out the time in which these frequency ranges are prominent.
[c,l] = wavedec(subject_2,7,'db2'); %level 7 decomposition approx = appcoef(c,l,'db2'); %approximation coefficient [cd1,cd2,cd3,cd4,cd5,cd6,cd7] = detcoef(c,l,[1 2 3 4 5 6 7]); %detail coefficients
%[P,f] = pspectrum(subject_2,400);
[P,f] = pspectrum(cd1,200);