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Re: [Discuss-gnuradio] UHD USRP2 full duplex mystery solved
From: |
Jason Abele |
Subject: |
Re: [Discuss-gnuradio] UHD USRP2 full duplex mystery solved |
Date: |
Mon, 14 Mar 2011 10:30:45 -0700 |
>>> 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
Re: [Discuss-gnuradio] UHD USRP2 full duplex mystery solved, Marc Epard, 2011/03/14