I've been playing around with an IR transmission system - basic pulsed LED to Panasonic detector module, with variable-length modulation pulses [250-900 usec on a 56.9khz carrier] - and I notice as you move the beams around/etc, that the received puslewidths tend to be somewhat susceptible to signal strength and beam angle.
So, I was wondering about how they get super reliable operation with TV remotes. Mine seems to not work at all [too far away, bounce off reflected surface, etc] or it gives the correct code every time. I know that some remotes use same-width pulse bursts with phase-modulation, while others use simple constant-period RZ codes with presence or absence of a pulse signalling 0 or 1, eg ...1.1.1...1.1...1.., etc.
This, plus my measures cited above, indicate that relative timing between pulses may be a more reliable measure than the width of the received pulses, given variations in intensity/distance/angle/etc.
Anyone know how to get the best reliability out of these things?
thanks for any help,
- dan michaels