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Re: [Discuss-gnuradio] GPS with DBSRX, Breakthough?

From: Gregory W Heckler
Subject: Re: [Discuss-gnuradio] GPS with DBSRX, Breakthough?
Date: Fri, 09 Mar 2007 14:21:15 -0500
User-agent: Thunderbird 2.0b2 (Windows/20070116)

Attached is a plot of the C/N0 estimates derived from the I & Q correlations from my software receiver. All SVs were set at a C/N0 of 50 dB-Hz in the simulation. As you can see they all converge (after the pull in period) to a C/N0 in the range of 46-47 dB-Hz. Decreasing the input C/N0 to 45 dB-Hz resulted in an estimated C/N0 of 44 dB-Hz. Similarly, a C/N0 of 40 dB-Hz on the simulator produced an estimated C/N0 of approximately 40 dB-Hz. The test configuration was the following:

Spirent GPS Simulator -> +40 dB Miteq Amp -> DB-SRX -> USRP

The DB-SRX was set to have 30 dB of RF gain and 30 dB of IF gain. I ran the same test with an external OCXO as the board clock and achieved the same results. I will make sure my C++ driver for the DB-SRX guarantees that the Max2118 comparator frequency is at least 250 kHz, clean up the code and submit.

PNG image

PNG image

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