Hello Eduardo, i have to mention i'm a newbie in this domain. but if i can help, no problem.
use e-mail contact me. Eddie 2011/7/5 Eduardo Lloret Fuentes <mall...@gmail.com> > Hello Eddie, > > I will try the same thing in a few weeks but using the USRP2 board. I hope > your work is going great. Do you mind if I contact you for advice? > > Greetings. > > Eduardo. > > 2011/6/24 Marcus D. Leech <mle...@ripnet.com> > >> ** >> On 06/24/2011 03:03 AM, Eddie Sun wrote: >> >> Thanks for the reply, but i still have some questions. >> >> 2011/6/21 John Andrews <gnu.f...@gmail.com> >> >>> >>> A USRP is a baseband IF receiver. Tune it to the GPS L1 frequency with >>> the right decimation rate so that you have your band of interest selected. >>> This should give you the IF signal. >>> >>> >> The source block that i used is the "UHD:usrp_source block" for USRP N210 >> in gniradio companion, after setting the frequency to L1 frequency >> 1575.42MHz, there is no "decimation" term can be set in the block(only >> usrp1_source and usrp2_source block have that term, not uhd), so should i >> use the "Rational resampler" block to instead of it? or other method to >> complete the decimation. >> >> The flow graph will only be >> "UHD:usrp_source block"→"Rational resampler"→"File sink" >> is that right? >> >> >> And I'm still a little confused, why i don't need to down convert the >> frequency but just do the decimation, i thought decimation is to slowdown >> the sample rate. >> >> Is that mean the flow graph output from "UHD:usrp_source block" is already >> a IF signal? If this is true, what is that signal frequency? It can't still >> have the 1575.42MHz if it's a IF signal, isn't it? >> >> Thanks, >> >> Eddie >> >> In UHD, you set the sample-rate of the source block, not the >> decimation. The UHD code determines the >> appropriate decimation to use based on what it knows about the device. >> >> The USRP hardware "stack" arranges for the signal of interest to appear as >> *complex baseband* signal, >> in which the signal goes from -bandwidth/2 to +bandwidth/2, which uses >> the "I" and "Q" signal >> representation. The "IF" is 0Hz in this case. You shouldn't need to >> re-sample to process the resulting >> baseband signal. This baseband "I and Q" signal format is *extremely* >> common in modern >> DSP systems for RF. For more background, you should look up the terms >> "direct conversion receiver", >> and "quadrature mixer" on Google. >> >> -- >> Principal Investigator >> Shirleys Bay Radio Astronomy Consortiumhttp://www.sbrac.org >> >> >> _______________________________________________ >> Discuss-gnuradio mailing list >> Discuss-gnuradio@gnu.org >> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio >> >> > > _______________________________________________ > Discuss-gnuradio mailing list > Discuss-gnuradio@gnu.org > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio > >
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