USRP IQ Sampling - Channel Confusion


I am slightly confused on the USRP configuration. The spec sheet says
there are 4 input and 4 output channels. Assuming you use two LFTX, and
two LFRX daughter cards, it makes sense that you have 4 input and 4
output channels since each daughtercard has a jack labelled A or B.

For IQ sampling with an individual antenna, would I connect the leads of
the antenna to an A and B channel on the LFRX for receive, and an LFTX A
and B channel for transmission?Â
To do simultaneous transmit and receive, would some type of external
switching circuit be required? If not, how would I go about doing this?