Sorry my ignorance, I revised my question and i was not clearly... There is a condition on line 1008 in usrp_standard.cc code. That condition limits the LO frequency (see my schematic) to the maximum of 44 MHz, OK? But you can read in the mailing list that the baseband frequency is limited to 4 MHz, then you are able to tx just 48 MHz (f_RX = f_baseband + f_LO = 4 MHz + 44 MHz = 48 MHz).
With my USRP using the BasicTX daughterboard I can tune my system until 248 MHz ( f_LO = 244 MHz + f_baseband = 4 MHz). My question is: How can the BasicTX tune up to 244 MHz if the usrp_standard doesn't allow to tune up it more than 44 MHz? (Sorry my poor english, I'm learning yet...) Thank you a lot, Ronaldo 2009/1/7 Ronaldo Nunez <ronaldo.vi...@gmail.com> > Than you Sebastiaan and Brian, I think that I understood it now. > I'm not sure but I think cordic is not available on tx path, is it? > > Thank for your answers, > > Ronaldo > > > 2009/1/7 Sebastiaan Heunis <sheu...@gmail.com> > > Hi >> >> I can help with the RX bit. Read up on undersampling. This is how >> you would do it with a BasicRX card. You can basically sample a >> signal higher than 64MHz provided that the bandwidth is less than >> 64MHz/2. The signal then ends up between 0 and 32MHz and is either >> inverted or not. You then need to set the cordic frequency to that >> frequency to mix it down to DC on the FPGA. >> >> With the TVRX cards there is a tuner that downconverts a high >> frequency signal (FM,UHF,VHF) down to somewhere below 64MHz (depending >> on which TVRX revision you have). >> >> Sebastiaan >> >> On Wed, Jan 7, 2009 at 8:17 PM, Ronaldo Nunez <ronaldo.vi...@gmail.com> >> wrote: >> > Hello Community, >> > >> > I read in the faq and in the usrp_stardard.cc that RF frequencies higher >> > than 44MHz can't be tuned in URSP, >> > so how BasicTX, and other daughter boards can tune hundreds, thousands >> of >> > MHz ? >> > >> > Thank you all, Regards... >> > -- >> > __________________________________ >> > Ronaldo A. Viera Nunez >> > Acadêmico/Engenharia Elétrica >> > Universidade Federal de Santa Maria >> > >> > Santa Maria - RS - Brasil >> > >> > _______________________________________________ >> > Discuss-gnuradio mailing list >> > Discuss-gnuradio@gnu.org >> > http://lists.gnu.org/mailman/listinfo/discuss-gnuradio >> > >> > >> >> >> >> -- >> Sebastiaan Heunis >> Radar and Remote Sensing Group, University of Cape Town >> Tel: +27 83 305 5667 >> > > > > -- > __________________________________ > Ronaldo A. Viera Nunez > Acadêmico/Engenharia Elétrica > Universidade Federal de Santa Maria > > Santa Maria - RS - Brasil > -- __________________________________ Ronaldo A. Viera Nunez Acadêmico/Engenharia Elétrica Universidade Federal de Santa Maria Santa Maria - RS - Brasil
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