Jim,
On 12/17/2014 01:46 AM, Jim Lux wrote:
On 12/16/14, 4:29 PM, Magnus Danielson wrote:
Jim, Bob,
There is a fair amount of work along the full path.
LNA with some L2 and L5 filters is pretty easy.
I think you still want to have a correlator baseband processing in say
an FPGA.
well, yes.. but I don't know if there's any handy open source free cores
out there for that.
I do know <grin> of an implementation that does the acq and track in a
pair of Xilinx 2-3000 parts and does the nav solution in a SPARC V8, but
it's not open source and it's definitely export controlled.
For that application it needs to break both the limits at the same time,
for sure.
Seems that what's out there is mostly "record bits" and "postprocess in
C++ or Matlab" Several textbooks even include it.
It's good for many purposes as you get yourself up to speed.
There is naturally stuff to be done on the L2C and L5 modulated signals,
but it goes in a relatively slow paze so that even modest processors can
keep up with it.
Indeed.. we do 24 channels (where channel is one PRN at one frequency)
with a 3 frequency solution without making a 66 MHz LEON2 based SPARC
sweat too much.
That's why it would be intriguing if someone had the FPGA stuff out there.
Indeed. I did a GPS correlator core once, but it had issues to fit the
FPGA I had at hand at the time. The software receiver I did was not at
all doing real-time, but it did do many of the crucial points and was a
nice exercise.
It would still be an expensive project, I suspect. Either you'd have a
few $50-100 boards that would need interfacing and a lot of time, or a
$1000 board with less time.
One hopes that in a few years, multifrequency stuff will become available.
Indeed. Maybe a complete implementation just needs to hit the web..
Cheers,
Magnus
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