Can anyone here let me know why the amplitude of the signal get distorted after it go through the CIC filter?
Is is due to the passband of the CIC filter is not flat?
I had try to cascade the CIC filter with compensator filter and i see the passband quite flat (+/- 4dB) but i still see the same problem. Can anyone help? Thanks.
Still unclear without knowing the CIC filter parameters and sampling frequency. But I think, it can happen with a low order CIC, if the decimated sampling frequency is near to an integer multiply of signal frequency. I would designate it an interference rather than a distortion.
P.S.: The decimated sampling rate is possibly too low to reproduce the sine waveform correctly. The numerical magnitude is probably constant or at least much less varying.