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

[Gregory W Heckler]

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.