Re: Anti Aliasing of Arbitrary Waveforms

glen herrmannsfeldt <gah@xxxxxxxxxxxxxxxx> writes:

Randy Yates wrote:
(snip)

Simply upsampling followed by downsampling buys you nothing. (It
actually costs you a little bit.)

However, upsampling, then performing a nonlinear function at that
upsampled frequency, then downsampling - yes, THAT buys you something.

You mean upsampling, non-linear function, filter, then downsample.

Yes.

I thought in the discussion there was one suggested that didn't
filter, but just selected every Nth sample.

Could be - I haven't followed this lengthy thread completely.

Otherwise, yes, downsample should include the appropriate filter.

If you didn't filter after the nonlinearity, you'd get a lot of
"trash" from the (non-aliased) harmonics in the upsampled signal
aliasing in to the downsampled signal - don't see that that would
help you too much. I.e., you must filter before downsampling.
--
% Randy Yates % "Though you ride on the wheels of tomorrow,
%% Fuquay-Varina, NC % you still wander the fields of your
%%% 919-577-9882 % sorrow."
%%%% <yates@xxxxxxxx> % '21st Century Man', *Time*, ELO
http://www.digitalsignallabs.com
.

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