Hi, I assume there is a reason to not use something like digikey 
PNA4614M00YB-ND?  (they come in a variety of carrier frequencies.)  I've 
used these with great results.  All the hassles solved for you in a 
$1.43 part.  Just FYI if you haven't seen them before.

J


William Chops Westfield wrote:
> Suppose that for the sake of miniaturization, I want to receive
> a typical IR remote control signal (~35kHz carrier, on/off modulated
> with minimum on/off times on the order of 1ms) using a bare photodiode
> running into a PIC A-D converter (or similar) and doing all the signal
> processing in software.  It seems like that should be about possible.
> 
> The signal I receive at the A-D is going to be a sum of ambient
> illumination plus noise sources (60Hz illumination, mostly) plus
> the signal I'm actually interested in.  Plus maybe other competing
> signals at slightly different carrier frequencies that I'd rather
> not see...
> 
> 1) If I know the carrier frequency I'm interested in, and I know
>     that I'm interested in on/off modulation, how do I pick the
>     minimum sample frequency I can get away with?  Presumably I
>     don't want an exact multiple of the carrier frequency.
> 
> 2) Does anyone care to point to a suitable DSP algorithm, hopefully
>     implementable on a typical integer microcontroller, that will do
>     the rest of the work I'm interested in?  This IS the sort of
>     thing that DSP algorithms can do, right?  If I need multiplies
>     and divides, can I pick a carrier frequency so that those end
>     up being shifts?
> 
> Thanks
> Bill W
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