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Re: [Discuss-gnuradio] transmitting two independent Signals

From: Eric Blossom
Subject: Re: [Discuss-gnuradio] transmitting two independent Signals
Date: Tue, 20 Feb 2007 07:45:29 -0800
User-agent: Mutt/1.5.9i

On Tue, Feb 20, 2007 at 03:41:31PM +0100, anmar wrote:
> hi all,
> we have been searching for a way to transmit two independent signals one
> on TxA and the other on TxB.

Using two daughterboards, you can send different complex baseband
signals out the A side d'board and the B side d'board.  You must set
nchan=2 in the usrp.sink_c constructor, and provide an interleaved
stream of complexes.  (Yes, the interface is a bit strange and ought
to be revisited/fixed.)  You can create the interleaved output stream

  u = usrp.sink_c(nchan=2, interp_rate=<interp>)

  src0 = <first complex source>
  src1 = <second complex source>
  interleaver = gr.interleave(gr.sizeof_gr_complex)
  fg.connect(src0, (interleaver, 0))
  fg.connect(src1, (interleaver, 1))
  fg.connect(interleaver, u)

  r0 = u.tune(0, u.db[0][0], freq_0)   # set center freq on side A d'board
  r1 = u.tune(1, u.db[1][0], freq_1)   # set center freq on side B d'board

> we have read the Tx_MUX documentation and tried some settings but we
> only could send two different frequencies two only 80khz!!! and we
> always have had two signals!
> what we like to do is is to chose the "two independent real signal" mode
> on the AD9862, how can we do that, just change the AD9862.h, or some
> different approach? if yes how to load it to the USRP.
> reading some of the forum questions, we understand that the gnuradio
> have the "Dual channel complex" mode and changing it would give
> conflicts with the FPGA and the software.

That's right.  If you're using a single Basic Tx daughterboard, and
you want independent real output out the I and Q, that'll take a fair
amount of hacking.  Using two daughterboards is going to be much, much
easier ;)

> is there some thing that we're missing or just not understanding.
> thanks,
> Wim & anmar


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