From: csilva1975 on 1 Mar 2010 18:32 Hello all. Let me say that i've learn a lot reading this articles. I'm designing a system that will (hopefully) sample an IF signal and decode it (AM, SSB, etc). At present I have the code in place to downmix it and downsample to 31 Khz fs. No problems here. After this step I whould like to low-pass filter it using a IIR elliptic filter. I've designed the filter (8th order), but after I apply the filter the amplitude of the signal get's real small, even for signals that are inside de passband. The amplitude of the signal before entering the filter are from -1 to 1, and after they are ranging from -0.004 to 0.14 inside the passband (yes, I have a small ammount of DC in the signal, but that's normal). The question is: why does this happen ? The response of the filter should be near 0 dB at the passband. I can post my matlab code, but it's a bit messy. Thanks in advance. Cesar PS - By the way, this is a hobby for me. Not homework nor a fancy commercial project.
From: csilva1975 on 1 Mar 2010 19:32 Hello again. I should be sleeping for the past couple of days ! I've figured out the answer. The reason that I start with a -1 ~ 1 signal and after filter it I end up with a small signal is because that the frequencies that lie in the passband are small. The larger signals are filtered (duh). Anyway, I'm sorry for this useless post. Keep up the good work! Cesar
|
Pages: 1 Prev: Accurate Harmonic Analysis Next: Compensating for gyro sensor drift |