Remember that you can actually let each base-station transmit at a
different code, and you can then monitor them that way. You could even
keep them frequency and phase locked or just monitor it and adjust it in
the post-processing. Such an approach would be a nice complementary
solution to the GPS/GNSS receivers. Also, it's "more of the same" which
helps in knowing your system.
Cheers,
Magnus
On 03/26/2015 06:32 PM, Robert Watzlavick wrote:
Thanks for the suggestion. Does the DSSS make it easier to correlate between
ground stations? I'm not sure how to handle the phase offset on the 10 MHz ref
clocks.
-Bob
On Mar 26, 2015, at 07:25, Attila Kinali <att...@kinali.ch> wrote:
On Wed, 25 Mar 2015 21:27:35 -0500
Robert Watzlavick <roc...@watzlavick.com> wrote:
I'm working on a project that I could use some advice on and also might
be of interest to the list. If it's not appropriate for the list, my
apologies.
The gods have apporved of your request. You may speak now.
;-)
I want to develop a tracking system for an amateur rocket that can allow
me to track the rocket even if onboard GPS is lost (as is typical during
ascent and sometimes during descent) or if telemetry is lost.
Given you can synchronize the clocks of the ground stations well
enough, then the rest is "easy". Then you can get away with having
a simple signal generator that only needs an XO. Or you can go
for a TCXO to make your signal processing life easier.
What you need to do, is actually the same as GPS does: Create a
direct spread spectrum signal and track it on all ground stations.
The DSSS has the advantage over the single pulse, that it's more
resilient against noise and interference. The disadvantage is, that
you have to have more complicated hardware. One viable way would be,
that you have precisly synchronized sampling systems (e.g. SDR's like
the bladeRF which can take an external clock) and then feed the data
to a PC where you do the heavy lifting. Then you don't need to build
custom hardware at least.
Also, if the precision by the DSSS signal is not good enough, you can
apply various tricks from the GPS world, like carrier phase tracking, etc.
HTH
Attila Kinali
--
It is upon moral qualities that a society is ultimately founded. All
the prosperity and technological sophistication in the world is of no
use without that foundation.
-- Miss Matheson, The Diamond Age, Neil Stephenson
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