[time-nuts] L1/L2 GPS Receiver

Jim Lux jimlux at earthlink.net
Fri Jan 17 22:09:31 EST 2014


On 1/17/14 11:35 AM, Magnus Danielson wrote:
> On 2014-01-16 20:29, Hal Murray wrote:
>>
>> anders.e.e.wallin at gmail.com said:
>>> The real benefit of dual-frequency is you can do post-processing with
>>> PPP.
>>> Javad has some modules but they start at 3 kUSD - if anyone knows of
>>> hobby
>>> level priced L1/L2 receivers that can produce rinex-files for PPP
>>> processing
>>> that would be interesting!
>>
>> Has anybody considered doing it in software?
>>
>> If I wanted to play with that sort of stuff, is there any particular SDR
>> hardware package/project that would good to start with?
>
> Well, considering that you will need to get the P(Y) signal at 10,23
> Mchip/s on both L1 and L2, requiring say 40 Msamples/s for both
> frequencies, and that you will need to do it for say 12 channeles and a
> bit of interesting processing beyond doing the same amount of channels
> for the C/A code, it will be an interesting challenge to do that in CPU
> code, rather than doing the "baseband-processing" in some form of
> hardware/FPGA.
>

ALmost certainly in an FPGA.  But unless you want fast acquisition, 
implementing the tracking loop and despreading in FPGA isn't 
mindbendingly difficult.  I'll bet there's open source out there.

You could also record raw bits and decode off line in software in 
non-real time, as long as your clock that you timestamp with isn't too bad.





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