Re: [Discuss-gnuradio] Fwd: RTL-SDR for GPS/Galileo signal reception

[Jean-Michel FRIEDT]

> I am collecting from the RTL-SDR dongle has amplitude in range
> of 0.04(peak to peak). Can we be sure of having GPS signal it and is such
> low strength of signal okay for GPS acquisition or not?

that's the beauty of spectrum spreading and pulse compression: despite
the signal being below thermal noise level, pulse compression by 1024-fold
(1.024 Mb/s and 1 ms code repetition rate) will increase signal to noise
ratio by 10 bits. So even a single-bit A/D converter (comparator) is enough
to collect GPS data. You cannot see GPS unless you compress the pulse (either
by squaring the signal to get rid of BPSK, or correlating with the local
copy of the Doppler shifted PRN).

JM

--
JM Friedt, FEMTO-ST Time & Frequency/SENSeOR, 26 rue de l'Epitaphe,  
25000 Besancon, France

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