Honored Contributor
Honored ContributorI am a bit lost now. Do you write code or does Matlab generate it. If Matlab then who decided the blocks above since you said you decided the analysis fir and reconstruction fir. Whoever put the blocks they are not in the right order.
The idea of QMF is to split up signal into two independent branches, one for low frequency content and the other for high frequency content. Then each branch can be processed at half sampling rate and once done the signal is reconstructed by upsampling then adding both branches. The key to split point is the decimation to half Fs. The key to recombine point is interpolation back to Fs. The general rule for decimation is apply filter then decimate. The rule for interpolation is add zeros then filter. If you reverse the order e.g. decimate to Fs/2 then filter it is not going to work due to sampling violation of high frequencies at Fs/2. Similarly if you interpolate by a filter then add zeros (or else add what?) then it is meaningless.
