[USRP-users] N310: Channel pairs are drifting in phase whith external LO setup

Janos Buttgereit janos.buttgereit at fh-muenster.de
Fri Mar 22 05:31:27 EDT 2019


after having struggled a lot with network config issues I finally got out N310 up and running. We chosed it for an application that needs perfectly constant phases between all four channels to build up DOA estimation applications.

I’ve set up an N210 as a signal source, outputting a sine round about 1.5GHz feeding a 4-way splitter that than feeds all four input channels of the N310. A Rhode&Schwarz signal generator outputting a 3GHz sine wave feeds a two way splitter that is connected to both external rx LO inputs.

From this setup I expect all four channels to maybe have a static phase offset that does not change over time. However, it can be noticed that the pairs of channels 0 and 1 and the pairs of channels 2 and 3 show those behavior but both pairs drift against each other over time. Any idea of what could be wrong with this setup?

I attached the GNURadio flow graph for this setup.

Thanks in Advance!
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