[time-nuts] CGSIC: FW: New NANU 2014090

[Henry Hallam]

The Swift Navigation Piksi project may be of interest:

http://swiftnav.com/piksi.html

It has an FPGA for correlation with an ARM Cortex-M3 for tracking
loops and navigation.  The hardware and ARM firmware is open source,
but the FPGA design is closed-source at the moment.  However, I don't
see why the FPGA would need adapting for use with L2C & L5.

I know the Swift Nav folks are looking into a multi-frequency product.
One of the main obstacles is a commodity front-end solution, and
antennas at reasonable prices.

Henry

On Tue, Dec 16, 2014 at 5:01 PM, Magnus Danielson
<magnus at rubidium.dyndns.org> wrote:
> 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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