On 03/03/2020 06:35 PM, Nick Foster wrote:
Nothing in the USRP will be damaged. It's up to you to ensure that
your subsequent RF chain will handle it. There are a few, rare
configurations which come to mind where it would be a Bad Thing to
suddenly pulse power on a millisecond timescale with extremely high
bandwidth.
1. Using your USRP to drive a linear accelerator (don't laugh, it's
been done)
2. Using your USRP to drive an extremely high power tube-based AM
transmitter
3. Using your USRP to drive an amplifier which is not unconditionally
stable
Outside of these you're probably fine.
Nick
Even there, it would very much depend on what the resulting
step-function looked like. I certainly wouldn't want to do the
experiment on,
let's say, the D-region radar at Arecibo :) :)
On Tue, Mar 3, 2020 at 3:21 PM Marcus D. Leech via USRP-users
<[email protected] <mailto:[email protected]>> wrote:
On 03/03/2020 06:16 PM, Sam Reiter via USRP-users wrote:
Hey Francisco,
Interesting question. I remember reading this when it was
initially posted, giving it some thought, and promptly forgetting
to respond. It's a question that is difficult to give a "yes" or
"no" to. Similar to statistics, I think the answer to this
question only comes by disproving the null hypothesis that "no
part of the signal chain is damaged with an underflow". If you
can't prove that damage will occur, then you're probably in the
clear, but you also can't be positive that the null hypothesis is
true. That being said, I don't think underflows are bad for the
hardware in any way.
An underflow is typically caused when a bottleneck on the host
side prevents data from filling USRP buffers quickly enough to be
pushed through the DAC at the requested rate. As I see it, the
only place in the signal chain that /might/ exhibit unexpected
behavior in the face of samples not being present would be at the
DAC (don't ask me why, but that would be my best guess). The way
UHD operates, the DAC and ADC are initialized and running as soon
as the streamer objects in UHD are initialized, and they sit
there processing nothing (similar to an underflow state) until a
TX stream command from the host tells the USRP radio core to
release it's queued samples to the converter(s).
Maybe that was all nonsense. In any case, I wouldn't worry about
radio damage, I'd worry about fixing your underflows :)
Best,
Sam Reiter
I'd have to agree with Sam here.
An underflow on the TX will just mean that whatever the DAC last
saw will be presented to the analog interface during the underflow
period.
Which means perhaps a few microseconds of no level change coming
out of the DAC. Not a problem at all, as far as I know.
The main thing is to optimize your code/computer-hardware to
prevent them.
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