N310 issue with LO offset when configuring two channels on the same subdev

[andrepuschmann]

Issue Description

I am using a two-channel setup (2 LTE cells), both 10 MHz next to each other in the 800 MHz band. I am not specifiying a subdevice for the N310 and I would expect that both cells are transmitted as intendenden on the two specified DL frequencies (cell1: 806 MHz and cell2: 796 MHz) because they both fall without in analog bandwidth of the board. I would assume that UHD takes care of setting the tuneargs to put the LO in middle of both channels so they both appear on the antenna ports. But this doesn't seem to be the case. Also note that the first cell at 806 MHz isn't visible so it seems the default is that the 2nd cell overwrites the tune args.

N310

With the X310 or when manually specifying the LO frequency to be in between the two cells I get the expected results.

X310:

Setup Details

• srsRAN 21.10 with 2 LTE cells next to each other
• 2x RF channel but no extra device args
• UHD_4.1.0.HEAD-0-g25d617ca

Expected Behavior

Two cells to be visible in the spectrum.

Actual Behaviour

2nd channel seems to overwrite LO config of first