Quoting Achilleas Anastasopoulos <[EMAIL PROTECTED]>: > > Quoting Achilleas Anastasopoulos <[EMAIL PROTECTED]>: > > >> I have a question/observation on this issue: > >> > >> Since the DDC multiplication is complex and since the internal DDC > >> oscilator is noncoherent, I do not see a difference between the MUX > >> settings: 0x33221100 and 0xf3f2f1f0. > >> > > >Is the difference between them a phase shift of 45 degrees and a gain > >ratio of > >sqrt(2)? > > Yes about the sqrt(2), but I guess the 45 degrees are irelevant here > since the operation is noncoherent so we cannt resolve the phase. > (see also comment below) > > > >> Similarly, with the setting 0x00003210 you will never be able to > >> separate the two channels coming from ADC0/ADC1 and ADC2/ADC3. > >> > > >You can seperate ADC0/ADC1 and ADC2/ADC3 if you set the DDC frequency > >to zero (I think you also have to never have set it to a non-zero > value >after powerup, since you can't reset the DDC phase) > > Even if you set the frequency to 0, there is a "random" initial phase > that is unknown, and thus you cannot separate the two channels. > > If x0(t) and x1(t) are the two inputs from ADC0 and ADC1 respect, then > the output is > > [x0(t)+j x1(t)] exp(j w_cordic t + phi), > where phi is unknown... > > I can't find the message, but I though that Matt Ettus stated that "phi" is zero at powerup, but it cannot be accessed thru software.
Matt? > >> Is this right? > >> > >> Thanks > >> Achilleas > _______________________________________________ Discuss-gnuradio mailing list [email protected] http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
