[time-nuts] Misuse of word "decimate" (was Re: Short term 10MHz source)
Hal Murray
hmurray at megapathdsl.net
Thu Jan 10 19:29:48 UTC 2019
petervince1952 at gmail.com said:
> Could you please clarify then exactly what "decimate" means in this context.
Perhaps an example will help.
Consider an audio input system. You want 0-20 kHz, so you need 40 k
samples/second. You also need a sharp cutoff filter at 20 kHz.
An alternative approach is to sample at 160 k samples/second and implement the
filter in software. You still need an external anti-aliasing filter, but this
one doesn't need to be sharp cutoff - just good enough to eliminate everything
over 80 kHz.
But now you have 160 k samples/second when you only want 40. The answer is to
throw away 3 out of 4 samples. That's decimation or downsampling.
You can downsample at non-integer rates by interpolating.
You can gain bits/sample with this sort of setup. I'm not sure how to explain
it.
--
These are my opinions. I hate spam.
More information about the Time-nuts_lists.febo.com
mailing list