Hello, Thank you for the useful information.
I have one more question. I am trying to receive GPS signal using RTL-SDR with GNU Radio. I am interested in L1 band of GPS signal (1575.42MHz). But I am confused about my sampling frequency. What value should I choose as samp_rate in RTL-SDR block of gnuradio? Thank you On Sat, Apr 7, 2018 at 5:56 PM, Kevin Reid <kpr...@switchb.org> wrote: > On Sat, Apr 7, 2018 at 1:31 AM, PRIYANKA PRIYADARSHINI < > priyankapriyadarshini...@gmail.com> wrote: > >> I am trying to receive a GPS signal and I am using RTL-SDR2832U, and an >> antenna with 40dB gain. >> >> According to my research, the signal coming from the satellite is at RF, >> and it gets downconverted in front-end to IF (Intermediate Frequency). >> >> Now, I need to remove that IF from the signal coming from the front end >> by multiplying it with the local generated carrier signal. For this, I want >> to know the exact value of the IF. But, I am confused that how can I get >> this? I also tried reading the data sheet of RTL-SDR but couldn't find the >> helpful information. >> > > You do not need to know the intermediate frequency to use an RTL-SDR. The > hardware finishes the conversion and gives you a digital signal at baseband > — that is, the center frequency is the frequency you requested, assuming > you're using the standard rtlsdr drivers. > > (Details: There are two different tuner schemes used in RTL devices > (depending on the tuner chip, not the RTL2832U chip). One of them actually > uses no intermediate frequency; the LO is set exactly to the frequency you > request, and the samples you get are directly from the ADC. It can be > recognized by the presence of a DC offset (center spike) in the obtained > signal. The other uses a nonzero intermediate frequency, but the digital > samples are digitally downconverted before they are sent to the host > computer.) > > Understanding IF is important to understanding how receivers are > implemented, and what imperfections they can have, but in GNU Radio you > generally do not need to consider the hardware's IF, whatever hardware you > are using, because the hardware or the driver takes care of it for you. In > some cases you need or want to do frequency shifts in software (such as to > avoid a DC offset, to receive multiple transmissions, or to work with a > subcarrier), but that'll be because of some property if *your* tuning or > the signal *you* know you're working with, not the hardware. > > _______________________________________________ > Discuss-gnuradio mailing list > Discuss-gnuradio@gnu.org > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio > >
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