[USRP-users] e310, RFNOC, GNURadio Full Duplex, Custom RFNOC Block

Andrew Payne wandrewp at gmail.com
Wed Jul 8 16:37:23 EDT 2020

I have an issue with my setup I'm hoping to solve.

I have an e310 running the UHD 3.15 LTS image.

I have created one custom RFNOC block, which has 2 RX streams, and it
is composed of the following chain: complex to magnitude ---> moving
sum ---> keep one in n (n=2048) ---> FIFO with input parameter SIZE=5,
so then I don't need the RFNOC FIFO block to save space when
generating the FPGA image file.  The moving sum block generates a sum
from a power of 2 samples, then I feed the keep one in n block with a
resulting sum whose LSBs are truncated, effectively dividing by a
power of 2 to effectively generate a moving average. I am using the
AXI Wrapper with Simple Mode, noc shell, etc, all generated from the
rfnoc mod tool.

It works great, but I also have a TX output signal, just a sine wave,
in my gnuradio flowgraph.  Its output, depending on the RF center
frequency, is greatly attenuated (the greatest I can get it is like
-39dBm, but it falls off to -55).  But if I just have the TX output
alone without my RX RFNOC block, I can get the output over 0dBm or
more, haven't tried going higher than that.

My question is, how can I get the TX signal higher with my full duplex
RFNOC setup?  Could anything about the RX chain be affecting my TX
samples, like could it be somehow deleting samples?  Do I need to tag
the streams in GNURadio so they don't interfere or something?


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