[USRP-users] Multiple independent tx streams?

Marcus D. Leech mleech at ripnet.com
Sun Sep 7 21:16:31 EDT 2014

On 09/07/2014 09:11 PM, Radio User via USRP-users wrote:
> I'm stuck, as my first notion of how to approach this problem is 
> clearly broken.
> Here's what I'm trying to do:
> On a B210, setup one TX channel to transmit a constant carrier at 
> (say) 5GHz.
> This carrier is on all the time.
> On the second TX channel, I will send a modulated waveform at 5.3681GHz.
> This may be a CW envelope, an SSB signal, whatever. At times I will 
> turn this
> transmit stream off entirely.
> My initial inclination was to setup two subdevices (A:A and A:B), then
> associate a stream with the modulated signal (using get_tx_stream with the
> channels field in the stream_args set to 0) and a second stream for the
> constant carrier (using a second call to get_tx_stream with the
> channels field in the stream_args set to 1).
> After hours of not getting this to work I found this nugget of wisdom 
> in the
> documentation for uhd::device::get_tx_stream  (but not in 
> uhd::usrp::mutli_usrp::)
>     Note: There can always only be one streamer. When calling
>     get_tx_stream()
>     <http://files.ettus.com/manual/classuhd_1_1device.html#a66d1bf289dd03a03df3860f3eee578c0>
>     a second time, the first streamer must be destroyed beforehand.
> So, I'm stumped.  Is it possible to treat the two TX channels 
> independently?  Right now,
> given that only one streamer can exist at a time, I can't even see how 
> to send
> different sample streams to channel 0 vs. channel 1.
> Any pointers?
> (This is part of an effort to build a minimal 10GHz transceiver with a 
> B210 and
> SoDaRadio.... I want to compare it to the not-so-minimal 10GHz 
> transciever that
> I've built with an N200, SoDaRadio, and a whole lot of other stuff...)
> rg
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> USRP-users at lists.ettus.com
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Look at tx_waveforms to get clues about creating a multi-channel 
"streamer".    While there can be only 1 streamer, said streamer may contain
   multiple streams....

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