Re: [Discuss-gnuradio] xcvr2450 and MIMO

[Matt Ettus]

On 01/18/2010 09:23 PM, Per Zetterberg wrote:
> Matt Ettus wrote:
> > On 01/18/2010 12:49 PM, Per Zetterberg wrote:
> > > Dear All.
> > >
> > > I think I read on the list that xcvr2450 doesn't support MIMO (frequency
> > > coherent transceivers to be more precise). However, when I search for
> > > xcvr2450 and MIMO in the archives I don't find any post on this.
> > >
> > > Can somebody update me on this ?
> >
> >
> > You CAN do MIMO with the XCVR2450. However, phased arrays (where you
> > need to know the absolute phase difference between boards) will be
> > hard due to the fractional-N synthesizer.
> >
> > The only board which is not MIMO capable is the TVRX.
> >
> > Matt
> That's great! But doesn't the same problem (fractional-N synthesizer)
> also apply to the RFX? I think I have seen this phase-shift. I have used
> my own db driver most of the time - does the proper driver fix this ?

There will be a phase ambiguity with all the PLLs, but there is a small 
number of possible phase differences with an integer-N PLL (roughly 
equal to the R-divider), while there are thousands with a fractional-N.

Matt