[USRP-users] TDD mode with USRPs in GNU Radio

Johannes Demel demel at ant.uni-bremen.de
Wed Feb 27 03:37:26 EST 2019


just to clarify some points here:

During transmission, there is always enough isolation to prevent damage.
Just use an antenna on the TX/RX port. Do not connect an antenna to the 
RX2 port. In this case it is always safe to operate a USRP?

In case I use GNU Radio and I just use the stream source and sink. (aka 
'UHD: USRP Sink' for transmission and 'UHD: USRP Source' for reception)
I want continuous reception but only burst transmission. Both source and 
sink are configured to use the TX/RX port. I send bursts to the 'UHD: 
USRP Sink' with a packet length which is translated to SOB and EOB tags 
for the USRP.
- Does the USRP do the switching at the start and end of burst 
automatically? Or does it switch to reception on RX2 permanently?
- Or do I need to use another sink?
- Where do I find the logic that takes care of switching? On the host or 
on the device?
I know I've asked similar questions before. I just want to clarify these 
questions again. Thanks!


Am 26.02.19 um 19:28 schrieb Marcus D. Leech:
> On 02/26/2019 12:10 PM, Andy Walls wrote:
>> Hi Marcus:
>> If one configures a USRP Sink to use the "TX/RX" port for Tx and a USRP
>> Source to use "TX/RX" port for Rx, does one still get both switches'
>> worth of isolation during Tx, or is it only the single switch's worth
>> of isolation in that case?
>> (I'm too lazy to run that down in the source code at the moment. :] )
>> Thanks,
>> Andy
> You still, as far as I can tell, get two switches worth, since the RX 
> channel is ALWAYS (as far as I recall) switched to the RX2 port during 
> TX, which gives you
>    two layers of switches regardless.

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