On Wed, 2011-05-25 at 12:14 -0500, John Andrews wrote: > Dear All, > > I have a question regarding the first complex multiplication process > with the IF sinusoid in the USRP. Which of the scheme mentioned below > is actually happening in the USRP?
I should also clarify -- USRPs are zero-IF quadrature receivers (excepting the TVRX daughterboards). The daughterboards (excepting the TVRX series) have quadrature outputs and send complex baseband signals to the two ADCs. --n > > > Let's say that two ADCs provide the sampled received signal to the > next stage of processing. Let's call the sampled stream of ADC_0 as A > and sampled stream of ADC_1 as B. > > > > > SCHEME-1 > > > The NCO produces two sinusoids that are in quadrature phase with each > other. These are sin(2*pi*f*t) and cos(2*pi*f*t). Let's call the > sin(2*pi*f*t)stream as C and > cos(2*pi*f*t) stream as D. The multiplier after the ADC stage does the > following. > > > 1. Multiplies the cos(2*pi*fc*t) stream, C, with the sampled data > stream of ADC_0, which is the stream named A and the product is AC. > 2. Multiplies the sin(2*pi*fc*t) stream with the sampled data stream > of ADC_1, which is the stream named B and the product is BD. > > > Then sends the resultant product from these two steps as a complex > sample, ( AC + jBD ) > > > SCHEME-2 > > > The NCO produces two sinusoids that are in quadrature phase with each > other. These are sin(2*pi*f*t) and cos(2*pi*f*t). The multiplier after > the ADC stage does the following. > > > The multiplier after ADC stage then multiplies the ADC outputs with > the NCO outputs as > ( A + jB ) * ( C + jD) = (AC - BD) + j(AD + BC) > and sends the above output as a complex sample. > > > Which one is true? > > > Thanks > > > > > > > > > _______________________________________________ > 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
