[USRP-users] LFRX with X310 I/Q Sampling

David Reuss david.a.reuss at gmail.com
Thu Jan 30 19:51:15 EST 2020


Hi everyone,
I have analog I and Q baseband signals of two CW tones I want to sample
with the LFRX daughterboard into an X310 with a simple grc flowgraph. I
have both RF ports hooked up to the LFRX (See LFRX.png) and have the subdev
set to A:AB for the USRP source block (see USRP_Source_Params.png).

When I only connect the I channel to antenna port A and configure the USRP
source block to look at antenna A I can see the sinusoids on the I channel
as I would expect (see One_Input_Param.png and One_Input_Result.png).

I then change the antenna to AB and connect both the I and Q channels. My
understanding is that this configuration should use antenna port A as the I
and antenna port B as the Q. I expected to see the sinusoids on both the I
and Q channels, but I instead see higher amplitude spikes on both channels
(See Two_Input_Param.png and Two_Input_Result.png).

Is there something wrong with my configuration or what I am trying to do? I
am using UHD version 3.15.

Thank you,
David
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