GPS on DBSRX

Question: Has anyone successfully acquired a GPS signal using the DBSRX
daughterboard? Is so, what kind of gain did you place before the board?

Thanks,

Chris

Question: Has anyone successfully acquired a GPS signal using the
DBSRX daughterboard?

Yes, several on this list have done so.

Is so, what kind of gain did you place before the board?

External to the dbs_rx I have an active patch antenna—its data
sheet says 27 dB gain, 1.5 dB noise figure. There’s also an
amplifier on the dbs_rx prior to the receiver chip, so the system
noise figure of the USRP itself should not be a problem.

Did you see my other email from April 4? I think it went out
to the list.

Cheers,
Peter M.

On 4/9/07, Peter M. [email protected] wrote:

Question: Has anyone successfully acquired a GPS signal using the
DBSRX daughterboard?

Yes, several on this list have done so.

Is there any version that is available for public ??

I would love to learn how its being done using GNU Radio!

Regards,

Rakesh

On 4/9/07, Peter M. <[email protected] mailto:[email protected]>
wrote:

 > Question: Has anyone successfully acquired a GPS signal using the
 > DBSRX daughterboard?

Yes, several on this list have done so.

Weird, I did not get Peter’s message. A quick look at
http://lists.gnu.org/archive/html/discuss-gnuradio/2007-04/threads.html
shows I did not receive a number of messages… and all this time I
thought I was being ignored.

Peter, your message containing “Yes, several on this list have done so”
did not make it to my inbox I’ll wait a day for it to appear in the
archives. Thanks for writing back. FYI I have an acquisition routine
that runs great on KD7LMO’s data, works great on my simulated data, but
does not work with the DBSRX hence all of my questions.

CHris

2007/5/23, Ben L. [email protected]:

for satellite PRN 18 with a code offset of 1988 as shown by the ‘spike’. The
gain for the dbsrx was 86 dB while using an active external antenna to get 28
dB more of gain. More details on my blog,

http://64.6.242.226/grblog/grblog.html

Not sure if I will have a link to the sample data because it is almost 2 GB
compressed, yikes! If you know how to break up the data let me know and I will
upload just the begininning of the file, since it is just over a minute of
data.

If anyone is interested, I have a complete coarse acquisition module
written for GNU Radio. The source code is available from
http://code.google.com/p/opengnss/. Some cleaning of the code is still
required. You can find images of the current results here:
http://trondd.blogspot.com/2007/05/opengnss-status.html

The current version has been tested against signals generated by a
Spirent GPS simulator. The recorded data files are available from
ftp://open-gnss.org/pub/opengnss/raw_gps_data.

Please let me know if you have any feedback.

Regards,

Trond D.

Chris,

I have successfully done coarse acquisition using the correlator
developed
here,

https://projects.cecs.pdx.edu/~icarroll/SoftwareGPSCorrelator/index.cgi/wiki

A plot of the ‘acquisition’ is here

http://64.6.242.226/grblog/uploaded_images/sat_18-714418.png

for satellite PRN 18 with a code offset of 1988 as shown by the ‘spike’.
The
gain for the dbsrx was 86 dB while using an active external antenna to
get 28
dB more of gain. More details on my blog,

http://64.6.242.226/grblog/grblog.html

Not sure if I will have a link to the sample data because it is almost 2
GB
compressed, yikes! If you know how to break up the data let me know and
I will
upload just the begininning of the file, since it is just over a minute
of
data.

Ben

Quoting Chris S. [email protected]:

2007/5/23, Trond D. [email protected]:

http://64.6.242.226/grblog/uploaded_images/sat_18-714418.png
data.

If anyone is interested, I have a complete coarse acquisition module
written for GNU Radio. The source code is available from
http://code.google.com/p/opengnss/.

I forgot to mention that you need some additional block for GNU Radio
that is not available in the stock distribution. Patches have been
sent to Eric B., but do not think they have been included yet.

Regards,

Trond D.

On Wed, May 23, 2007 at 11:42:29PM +0200, Trond D. wrote:

I forgot to mention that you need some additional block for GNU Radio
that is not available in the stock distribution. Patches have been
sent to Eric B., but do not think they have been included yet.

My bad. I’m tied up the rest of today.
I’ll see if I can’t get them in tomorrow.

Eric

Trond,

If anyone is interested, I have a complete coarse acquisition module
written for GNU Radio. The source code is available from
http://code.google.com/p/opengnss/. Some cleaning of the code is still
required. You can find images of the current results here:
http://trondd.blogspot.com/2007/05/opengnss-status.html

Awesome, I would like to try it out, what is the best way to get the
needed
blocks assuming they are not in a patch already?

Any thoughts on the next step of tracking?

Also, if I want to test it from my captured files would I change line 85
of
acquisition.py to pull from a file or is this done somewhere else.
Thanks.

Ben

Ben L. wrote:

Chris,

I have successfully done coarse acquisition using the correlator developed
here,

Ben,

Thanks for the reply. I now have a GPS acquisition routine and tracker
running. I am using the DBSRX with about 60dB of gain on a “puck” style
antenna. My trackers are producing the nav bits, but I still need to
decode them (I plan to use GPStk for this). It is all implemented as a
single gnuradio block. I will release the source when I get smart on
the subject and get a final thumbs up from my company (which paid for
it).

Chris

2007/5/24, Ben L. [email protected]:

Any thoughts on the next step of tracking?

I want to try both the BASS tracking described by James Bao-Yen Tsui
in Fundamentals of Global Positioning System Receivers: A Software
Approach and a conventional PLL based tracking module.

But before I can get down to tracking, I have to implement the fine
frequency estimation.

Also, if I want to test it from my captured files would I change line 85 of
acquisition.py to pull from a file or is this done somewhere else. Thanks.

Take a look at the gr_gnss-acquistion-test.py script in the scripts
folder. Basically this is all you need:

    file_src =  gr.file_source(gr.sizeof_gr_complex,

“…/data/L1-4MHz-svn1-nav.dat”)
self.acquisition = acquisition(fs=fs, svn=1, alpha=alpha)

    self.ca_sink = gr.vector_sink_f()
    self.fd_sink = gr.vector_sink_f()
    self.rmax_sink = gr.vector_sink_f()

    self.connect( self.src,  self.acquisition)
    self.connect( (self.acquisition, 0), self.ca_sink )
    self.connect( (self.acquisition, 1), self.fd_sink )
    self.connect( (self.acquisition, 2), self.rmax_sink )


Trond D.

2007/5/24, Chris S. [email protected]:

antenna. My trackers are producing the nav bits, but I still need to
decode them (I plan to use GPStk for this). It is all implemented as a
single gnuradio block. I will release the source when I get smart on
the subject and get a final thumbs up from my company (which paid for it).

Chris

I am very excited to see the result once it is released! I just wanted
to mention some of the differences between this and my approach. I am
trying to keep as much as possible at GNU Radio level, and thereby
exposing as much of the internals as possible at Python level. This
has proven to be harder that initially assumed due to the lack of
message passing functionality[1] and the possibility to reconfigure a
running graph.

My main target is research and development, so to have access to all
parts of the receiver in a high level language is a great advantage.
Since it is also a goal to be able to experiment with sensor
integration such as INS, a modular system is also an advantage. If
anyone wants to get together and discuss GNU Radio and GNSS, I will be
at ION GNSS 2007 in September; hopefully the OpenGNSS will have gained
more functionality by then :slight_smile:

[1]. I have looked into message queues, but it is not what I am
looking for. Mblocks might be the answer, but they were not available
in March.

Trond D.

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