Hello,
I'm trying to figure out how the AGC operates in my setup of GNU radio
(3.10.5.1), gr-uhd (UHD4.3), and USRP B205-mini-i, but it seems to too
complex to figure out.
My application is to receive signals from a multitude of bursty
transmissions. The default AGC seems to generate large peaks at the
beginning of frames, which is not so good. So, I was trying to look for
ways to make it work better.
I have been looking at the source code for the gr-uhd, uhd library, and
AD9364 documentation, but it is not so easy to find out how it works,
since gr uses the usrp-multi interface, which hides the details of
accessing the actual radio interface.
First of all, it seems that it is impossible to find the current gain of
the RX if AGC is enabled, even though according to the IC document, the
gain settings should be available even in the AGC mode. So, maybe this
is a shortcoming of the gr-uhd implementation, which does not query the
IC for the gain setting. This would allow me to use the knowledge about
the gain values in further processing.
Secondly, the seems to IC support advanced configurability of the AGC
from choosing between fast and slow AGC and manual gain settings to
tuning the parameters of the AGC function inside the IC. But
unfortunately none of this seem to be exposed in the UHD library. This
could allow tuning the AGC to behave better for my signals.
I could try to work out something myself, but I was unable to find any
documentation about how the UHD library is layered, and how the
high-level functions eventually interface with the different radio IC:s.
It is certainly possible to find out all of it from the source, but
having some documentation or pointers to the right direction would make
it all much easier.
It is always possible to implement the AGC function in GR by setting the
gr-uhd to use manual gain, but I'm a bit afraid that the loop could be
too slow.
Regards, Ville
--
Ville Eerola
ville.eer...@iki.fi
050-4804435
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