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Author [OT] digital filtering question
Steve Amphlett

2006-10-30, 7:42 pm

I know I should be asking this somewhere else, but I have a feeling
that regulars here will either know the answer or be able to point me
to a good source...

If I have some evenly sampled data with the sample rate doubled
during an interesting section, how can I filter it? If I just use
filter() or filtfilt(), the frequency response will change during the
"dense" bit. This probably isn't a problem, but I'm concerned about
what happens when crossing from the "sparse" bit to the "dense" bit.
Am I likely to see ringing ... or worse?

tia.

- Steve
Steve Amphlett

2006-10-31, 4:07 am

Paul Mennen wrote:
>
>
> Steve Amphlett wrote:
>
>
> It's hard to be very analytical about it with a
> sample rate change in the middle of your data
> stream. If possible, you should interpolate the
> slower portions by two so that it matches the
> data rate of the faster data before applying
> the filter. Even a simple interpolator (i.e
> inserting zeros, or repeating points, followed
> by a modest interpolating filter) would be better
> than trying to interpret results using the mixed
> data stream.


I feared as much. Thanks for taking the time out to reply. Much
appreciated.

- Steve
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