I am using Flex-2400 boards and the received signal is ideally at baseband which in fact is not possible because, of various factors. Now, we have a signal that has a center frequency 'fc' which is not 0Hz. Assuming the costas to lock at this carrier I can achieve my goal. Isn't it right?
Can you also tell me how fmax and fmin are calculated? For example, dbpsk.py has fmax=0.1 and fmin=-0.1. How do we get these? Thanks, Ali On Wed, May 27, 2009 at 8:24 AM, Tom Lutz <[email protected]> wrote: > > > > As in Gnuradio there is no such thing as a carrier as the signal is in > > baseband what will the output of costas loop be so as to use it to get > the > > Spreading sequence. > > I am sorry my concepts are not very strong but I am learning and such > > unresolved questions make this learning all the more difficult. Can you > > please tell me where I am wrong and what could be done. > > The costas loop block (the one found in GRC and in the source code, > assuming you are using that one) actually outputs the incoming signal > multiplied by the synchronized carrier (assuming it has locked). If > you tune the USRP off of the carrier you are interested in, that would > probably work, but that's from my naive view of the world. For > example, if your carrier was at 465MHz and you tuned to 464MHz, you > might be able to bandpass filter and send to the costas loop the 1MHz > carrier. The costas loop would output the downmixed signal downmixed > further, such that baseband is now 465MHz. > > The min/max frequencies for the costas loop are in radians/sample, FYI. > > Tom >
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