Re: [Discuss-gnuradio] tx mux explained!

[Eric Blossom]

On Fri, Aug 26, 2005 at 11:43:01AM -0400, Chuck Swiger wrote:
> At 04:12 PM 8/25/2005 -0700, you wrote:
> >On Thu, Aug 25, 2005 at 03:40:13PM -0400, cswiger wrote:
> >> I guess the most direct question is: with a tx mux of 0x0008
> >> why am I getting any signal out of J49?   Only DAC0 should
> >> be enabled, and connected to the I output of DUC0.
> >>
> >> --Chuck
> >
> >Good question.  The answer is a bit involved.  Let me try and explain.
> >
> >First, take a look at figure 3 on page 19 of the AD9862 data sheet.
> >It shows the components of the transmit path in the AD9862.
> 
> Thanks Eric  - I owe you a pizza ;)
> 
> So it's like my earlier question about the rx with real in (Q=0) / complex 
> out, since blocks E and B are enabled.

Yes.

> Appearently we can use the coarse modulator (typo in the manual
> calls it block 'D') with "Two Independent Real" application mode,
> tho it may get really weird with the software and fpga expecting
> "Dual Channel Complex" mode. I'll stick with mux = 0x0098 for now.

It would take some work, and you'd also need to build the DUC in the
FPGA.  We have tested the FPGA based DUC in the (distant) past, and as
you may have noticed, there is #ifdef'd code in the host library to
deal with it.

Eric