Thank you Eric, I think that the things are going to be clearly in my head now.
"returns the actual baseband frequency that corresponds to DC in the IF." what this means? The baseband frequency is the frequency of the signal(a tone, a constant, noise, file, music...) that i want to tx, isn't it? Why does it correspond to DC in IF? I would like to know if I send want tx a signal of 1MHz at 100 MHz, i need to upconvert it 99 MHz. So what are the values of the COARSE MODULATOR and the value of FINE MODULATOR for that frequency (99MHz)? Regards, Ronaldo 2009/1/14 Eric Blossom <[email protected]> > On Wed, Jan 14, 2009 at 12:31:30AM -0200, Ronaldo Nunez wrote: > > Thank you for your answer Mr. Blossom, > > > > > Please read the USRP FAQ then ask again if you're still not clear. > > > > > http://gnuradio.org/trac/wiki/UsrpFAQ< > http://gnuradio.org/trac/wiki/UsrpFAQ> > > > > http://gnuradio.org/trac/attachment/wiki/UsrpFAQ/USRP_Documentation.pdf > > > > Sorry, but, I read all FAQ, and i just found the answer of my third > question > > ("And for the other dboards, how tune() works for them?") > > > > > Have you looked at the code that implements tune? > > > > > > Eric > > > > usrp_stardard.{cc,h}? Yes... > > > > I (think) understood the tune process when I read it. > > > > First, the "tune()" tells to d'board to tune as close as it can. After, > with > > the result of that operation (maybe, f_db - f_target = f_duc) "tune()" > > configure the DUC. Is that right? (Be free to correct me...) > > > > But, the BasicTX doesn't have a PLL, or a VCO or another component to > tune > > at a frequency...Should FPGA do tune job for the basicTX? > > Correct, it doesn't have a PLL or VCO, but it does have a set_freq > method that behaves exactly as specified. That is, it attempts to > tune as close as it can and returns the actual baseband frequency that > corresponds to DC in the IF. > > struct freq_result_t > db_basic_tx::set_freq(double target_freq) > { > // Set the frequency. > // > // @param freq: target RF frequency in Hz > // @type freq: double > // > // @returns (ok, actual_baseband_freq) where: > // ok is True or False and indicates success or failure, > // actual_baseband_freq is the RF frequency that corresponds to DC > in the IF. > > struct freq_result_t args = {false, 0}; > args.ok = true; > args.baseband_freq = 0.0; > return args; > } > > The end result of this is that there is no special case and all the > tuning ends up getting done in the DUC since no matter where you ask > it to tune, it returns 0 Hz. > > Eric > -- __________________________________ Ronaldo A. Viera Nunez Acadêmico/Engenharia Elétrica Universidade Federal de Santa Maria Santa Maria - RS - Brasil
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