Comment by addaon

Comment by addaon 14 hours ago

2 replies

Yep, 200 m is pretty close to standard. Which is why 32 channel and 20 kHz is a pretty common design point. But customers would love 64 channel and 40 kHz, for example. Also, it's worth noting that if your design range is 200 m -- your beam doesn't just magically stop beyond that. While the inverse square law is on your side in preventing a 250 m target from interfering with the next pulse, a retro-reflector at 250 m can absolutely provide a signal that aliases with a ~16 m signal (assuming 234 m time between pulses) on the next channel under the right conditions. This is an edge case -- but it's one that's observable under steady-state conditions, it's not just a single pulse that gets misinterpreted.

CamperBob2 9 hours ago

Don't these things use Gold codes or something similar to eliminate temporal aliasing problems? I guess that wouldn't make multipath issues go away completely, but it could fix the case you're referring to.

  • addaon 9 hours ago

    You can, and we did an extremely limited form of that — see other comment on reducing correlations. But you have an energy limit from eye safety concerns, so energy spent on spreading the signal over time and modulating it directly takes away from power giving range. And doing non-trivial modulation isn’t easy — most of these pulses are generated by a capacitive discharge, which limits shaping.