Re: [Discuss-gnuradio] UHD USRP2 full duplex mystery solved

[Marc Epard]

Thanks, Jason. I should have posted our observations back when we made them. 
We're doing okay with the two-USRP setup, but it's good to have options.

-Marc

On Mar 14, 2011, at 12:30 PM, Jason Abele wrote:

>>>> However, the WBX has enough internal leakage between tx and rx that we
>>>> gave up on single-daughterboard full duplex.
>>>> 
>>> 
>>> Just a heads up, you had not tried WBX without C1 installed on the
>>> grand-daughterboard, or even without the grand-daughterboard at all,
>>> just using J202 and J201 on the main WBX board, you might see if one
>>> of those scenarios could meet your tx-rx isolation requirements.
>>> 
> 
> Sorry, missing and *if* in there ( ... Just a heads up, if you have not ... )
> 
> Basically, C1 allows for reception on the TX/RX antenna port, it
> connects the two T/R switches.
> 
> However, if you are looking to do full-duplex, you will not be
> receiving on the TX/RX port anyhow, just RX2.  So rather than having
> an implicit leakage path through the T/R switches (RF switches rarely
> give more than 20-30dB isolation, depending on frequency), you can
> remove C1 on the grand-daughterboard and improve isolation at the
> expense of not being able to receive on the TX/RX port.
> 
> If you want to go even further, you can remove the grand-daughterboard
> entirely and install SMA connectors in J201 and J202.  You will also
> need to move a capacitor to AC couple J201 and J202 to the circuit.
> 
> Jason
> 
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