[time-nuts] Need advice for multilateration setup
rocket at watzlavick.com
Thu Mar 26 22:43:32 EDT 2015
On 03/26/2015 01:56 PM, Jim Lux wrote:
> The key is that you don't need *real time* position.. a few seconds or
> minutes delay is probably ok, right?
Seconds are probably ok, minutes might be a little long. PCs are pretty
fast though these days for signal processing I would think.
> To compensate for the receiver variability, simultaneously transmit a
> signal with a different PN code, at the same frequency (roughly) as
> the rocket's transmitter.. The receiver will receive both, but the
> signal from your ground reference transmitter isn't moving, so you can
> use the "non-rocket" signal as a calibration reference.
Now I didn't think of that - so you're saying to send another signal
from a central ground station to all the receivers and then have them
use that as a relative reference? Since I'll know where each ground
station is, I should be able to subtract off the TOF so each station has
a common reference point. That's a pretty cool idea.
> What's your budget?
I was thinking in the $1k range so that would be about $200 per ground
station. A couple of controllers I was considering for the ground
stations include the Netburner MOD54415 (same one I'm using for the
flight computer) or the BeagleBone Black. Both of those are under $100
and have counter/timers onboard although I have to see what the max
clock rate is. As long as the channel-to-channel delay wan't too bad, I
think using a 12-bit ADC to digitize the two signals would work because
you can interpolate to get a higher-resolution zero crossing.
More information about the time-nuts