Re: [Discuss-gnuradio] gnuradio 101

[Martin Dvh]

cswiger wrote:
> One thing I don't understand tho: if a typical mux of
> 0xF0F0F0F0 feeds zeros to all DDC Q inputs, and ADC 0
> to all DDC I inputs, nchannels = 1 sends data from DDC 0
> only, and looking at the DDC block diagram in figure 3 at:
>
> http://www.gnu.org/software/gnuradio/doc/exploring-gnuradio.html
>
> how is it we can a complex stream to the software? Why aren't
> all the Q values also 0 ( zero * nco-cos ) ?    Is the
> decimating low pass filter also a hilbert?
I think simple complex math:
out.complex=ADC.complex * NCO.complex
out.real=ADC.real*NCO.real - ADC.imag*NCO.imag
out.imag=ADC.imag.NCO.real + ADC.real*NCO.imag

ADC.imag=0 ==>
out.real=ADC.real*NCO.real
out.imag=ADC.real*NCO.imag

Greetings,
Martin