Anyone do you know good GPS receiver Method?

GNU Radio
1

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$B!!(Bexist .
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

$B!!(BGPS L1$B!!(Bsignal $B"(B USRP N200
$B"!!(Bgnuradio-companion(UHD_source$B"(BFile_sink)
$B"!!(Bsoftware decode soft $B"*!!(Boutput(Location data)

Eventually$B!!(BI want to Calculate location data,
Please let me know if you’re a good$B!!(Bthis way

I am sorry that My English is not good

Kouki

2

2011/11/18 山本弘貴 [email protected]:

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

3

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:”

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

4

On Fri, Nov 25, 2011 at 7:01 AM, Nick O. [email protected]
wrote:

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.

I’ve successfully used a DBSRX + active antenna to receive GPS signals
before. What software are you using to do the correlation and find the
L1 signal?

–n

5

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

6

I had never heard of fastGPS; sounds pretty useful. What is the end
goal
for your receiver?

Ryan

7

Positioning… :slight_smile:

8

I am using fastGPS to do the correlation as well as writing my own
MATLAB
correlation scripts.

Nick