Re: [Discuss-gnuradio] Anyone do you know good GPS receiver Method?

[Nick Othieno]

Hi Ryan,

What did you use for your setup, ie daughterboards, antenna and LNA (if you do not mind my asking). I have been trying a setup for months that uses a DBSRX2 and a mighty mouse 2 antenna only, but I have never been able to acquire the L1 signal. I am wondering where I have gone wrong in the setup.

Nick

On Fri, Nov 18, 2011 at 9:47 AM, Wolfarth, Ryan <address@hidden> wrote:

Hi folks,

My group is using USRPs to do the task Kouki described, although our flow diagram is a little different.  We only use the USRP2 to receive the raw RF data which is written to file.  This data is processed to the point where we decode the navigation bits, but no position is ever found.  We're more interested in the effects of ionosphere scintillations on GNSS signal structure so we don't need to calculate antenna position.

I can recommend two books that have helped me immensely.  The Kaplan "blue book:"

http://www.amazon.com/Understanding-GPS-Principles-Applications-Second/dp/1580538940/ref=sr_1_1?ie=UTF8&qid=1321627222&sr=8-1

And the Kaplan "blue book:"

http://www.gpstextbook.com/

I do know of a group that has used a USRP1 to develop a 4 channel L1 receiver, but they had to modify the FPGA to do all the real time processing.  Let me know if you have additional questions!

-Ryan

On Fri, Nov 18, 2011 at 7:56 AM, Brian Padalino <address@hidden> wrote:

2011/11/18 山本弘貴 <address@hidden>:

> Hi, All
> I have  very trouble
> My experiment enviroment isUBUNTU 11.04 , USRP N200, DBSRX2 ,active
> antenna and gnuradio
> I am worrying about good software GPS receiver is not　exist .
> I want to receive L1 signal , and want to demodulate that signal
> However GPS signal is used  Spread spectrum modulation scheme.
> I try to creating gnuradio-companion's blocks.(use to Spread spectrum
> demodulation blocks)
> but that is very difficult so Now I think method is
>
>　 GPS L1　signal → USRP N200 →　gnuradio-companion(UHD_source→File_sink)
> →　software decode soft →　output(Location data)
>
>
> Eventually　I want to Calculate location data,
> Please let me know if you're a good　this way

I recently came across this product listing at Spark Fun:

   http://www.sparkfun.com/products/10981

Which has a link to a book all about GPS receiving and even comes with
MATLAB source code:

   http://www.amazon.com/Software-Defined-GPS-Galileo-Receiver-Single-Frequency/dp/0817643907

I am sure, with the source, you could adapt it to use the USRP
recorded signal, and then possibly port the MATLAB over to either
Python (using Josh's signal processing in Python blocks) or straight
C++.

> I am sorry that My English is not good
>
> Kouki

Good luck - it's definitely not a trivial task, but it sounds extremely fun.

Brian

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