Re: [Discuss-gnuradio] Re: Tx Path

[Eric Blossom]

On Tue, Apr 17, 2007 at 07:25:50AM -0700, Eric Blossom wrote:
> On Tue, Apr 17, 2007 at 08:55:08AM +0200, Anmar wrote:
> > Brian Padalino wrote:
> > 
> > > I believe you may be able to send 2 real signals and control their
> > > phases, but someone else here is a better authority on that than I am.
> > 
> > Do you know who that is?
> > 
> > I found a patch that Patrick has posted for phase shifting, put it 
> > didn't work, Did someone tried to use it, and have got it working?
> > 
> > Thanks
> > Anmar
> 
> If you have two daughterboards you can send two independent signals.
> 
> If you start fresh from USRP power-up you can control the phase
> between the transmitted signals (this also depends on the
> daugherboards that you are using and how they are configured.)  The
> power-up requirement is because from software we have no way to
> control the phase accumulator in the AD9862 digital upconverter,
> however at power-up it has a constant value.
> 
> Eric

Following up with "more information than you probably want"...

If you're willing to do some work, it is _possible_ to reprogram the
AD9862 such that the two signals sent to it are treated as two
independent real signals.  This only makes sense using a
non-quadrature Tx daughterboard (e.g., Basic Tx or LF Tx).  However if
you do this, you lose the use of the digital upconverter in the
AD9862.

You can work the details out by looking at the existing code in
usrp_basic.cc and usrp_standard.cc and spending a few hours with the
AD9862 data sheet ;)

Eric