impact of noise in zero-padded region of filtered time trend data

Started by all4dsp October 17, 2012
On Wed, 17 Oct 2012 23:28:47 -0500, all4dsp wrote:

>>> It is a bit unconventional, and there are pitfalls to what you're >>> doing > >>> (mostly involving the fact that your sampled time sequence input and >>> output aren't what a continuous-time filter either sees or spits out). > >>> As long as your sampling rate is high enough compared to your filter > (and >>> signal) bandwidth there's a good chance that you're OK. >> >>I agree. >> >>-- glen >> >> > I understand one wants the sampling rate higher than the signal > bandwidth to prevent aliasing. But, what problem arrises as the sampling > rate approaches the filter bandwidth? And, generally, what would be a > good minimum ratio of sampling rate to filter bandwidth?
Wow. Good question. I just know it's something to be avoided. Hmmm. Come to think of it, if the filter is going to do anything significant to the signal, it'll have to have a bandwidth considerably (over 10 times) narrower than the sampling rate. Otherwise the filter's frequency-domain response isn't going to have the chance to drop much toward zero. -- Tim Wescott Control system and signal processing consulting