I have a problem of distortion while filtering.
I have a signal with bandwith of 10 KHz centered on a carrier frequency
of 30 KHz without noise.
I'm trying filtering that with a butterworth filter of signal bandwith of 40 KHz centered on 30 KHz using
But if i try to compare x and y they are different even if the filter should be non distorting for the signal.
If i consider 10*log10(mean(x.^2)/(mean((x-y).^2)) i find something like 15 dB and the errors are concentrated on the firsts and lasts samples.
How can I create a not-so-distorting filter?