Re: [USRP-users] Can underflows in any way be bad for hardware in the long term?

[Marcus D. Leech via USRP-users]

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 
mailto:usrp-users@lists.ettus.com>> 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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Re: [USRP-users] Can underflows in any way be bad for hardware in the long term?

[Nick Foster via USRP-users]

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

On Tue, Mar 3, 2020 at 3:21 PM Marcus D. Leech via USRP-users <
usrp-users@lists.ettus.com> 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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>
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Re: [USRP-users] Can underflows in any way be bad for hardware in the long term?

[Marcus D. Leech via USRP-users]

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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Re: [USRP-users] Can underflows in any way be bad for hardware in the long term?

[Sam Reiter via USRP-users]

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

On Tue, Feb 11, 2020 at 6:32 AM Francisco Albani via USRP-users <
usrp-users@lists.ettus.com> wrote:

> Hi!
>
> I've been using USRPs many years yet it never occurred to me to ask that
> question.
>
> Of course one should avoid using an application in a regime of many
> underflows, BUT, just for the sake of the question suppose I came up with a
> setup that does what I want while throwing a lot of them, are there any
> implications to the weariness of any piece of hardware? For example turning
> on and off the TX chain.
>
> Will a radiation environment change the conclusion?
>
> Bye and thanks for your help!
>
> Francisco.
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[USRP-users] Can underflows in any way be bad for hardware in the long term?

[Francisco Albani via USRP-users]

Hi!

I've been using USRPs many years yet it never occurred to me to ask that
question.

Of course one should avoid using an application in a regime of many
underflows, BUT, just for the sake of the question suppose I came up with a
setup that does what I want while throwing a lot of them, are there any
implications to the weariness of any piece of hardware? For example turning
on and off the TX chain.

Will a radiation environment change the conclusion?

Bye and thanks for your help!

Francisco.
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