On 03/21/2018 03:51 AM, Brais Ares via USRP-users wrote:
Hi,
I can see a similar spike, a few microseconds long, at the beggining
of each transmission (see figure attached).
However I'm not using a B2xx, but a *E310*. Could this also be a
hardware problem or just its normal behaviour?
Regards.
Brais.
Small transients at the beginning and end of transmissions are pretty
normal -- with both analog hardware and DSP contributions to the
phenomenon.
The various pieces of analog hardware (mixers, switches, amplifiers,
synthesizers) cannot reach steady-state operation instantaneously, so
there will
always be some transient from that. Further, the filters in the DUC
chain will necessarily experience a transient as new data is loaded into
them that
is completely unrelated to any previous samples--they will be
processing a discontinuity in signal, and there will be some transient
response as a result.
2018-03-15 20:56 GMT+01:00 Michael West via USRP-users
<usrp-users@lists.ettus.com <mailto:usrp-users@lists.ettus.com>>:
Hi Thomas,
This is a known hardware issue with earlier revisions of the
B200mini and has been fixed on newer versions. Please contact
supp...@ettus.com <mailto:supp...@ettus.com> and they can help get
the boards reworked.
Regards,
Michael
On Sun, Feb 25, 2018 at 6:54 AM, Thomas Teisberg via USRP-users
<usrp-users@lists.ettus.com <mailto:usrp-users@lists.ettus.com>>
wrote:
I'm sorry, which thread are you referring to?
I have tried implementing the changes in the thread I
originally linked to and it doesn't seem to have made any
difference.
Best,
Thomas
On Feb 25, 2018 4:52 AM, "Steven Knudsen" <ee.k...@gmail.com
<mailto:ee.k...@gmail.com>> wrote:
Hi,
This is a known problem with the B20xmini. Have a look at
this thread and then follow it up.
You are right, you are seeing caps charge and discharge,
basically.
Since I made the changes myself on my units, I am not sure
where things were left with Ettus and their policy for
fixing the problem. But I can say that once you make the
changes, the transients are gone and the minis work really
well.
regards,
steven
On Sat, Feb 24, 2018 at 3:25 PM, Thomas Teisberg via
USRP-users <usrp-users@lists.ettus.com
<mailto:usrp-users@lists.ettus.com>> wrote:
I'm working on a radar project that requires sending a
series of short pulses. Looking at the pulses on a
scope, I'm seeing large voltage spikes at the
beginning and the end of each transmission.
As shown in the attached screenshot, before the
transmission starts, there is a 90 mV spike lasting
about 10 us. After the transmission, there's a -25 mV
spike lasting about 20 us.
The setup for this is simply a USRP B205mini-i
connected to a 50 ohm input on a scope through a 30 dB
attenuator. The signal is at 435 MHz with the scope
sampling at 20 Gsps.
Our initial thought was that we must be seeing some
effects of some of the RF frontend components turning
on and off. I found this previous mailing list post
and tried the suggested fix in b200_impl.cpp but
nothing changed:
http://lists.ettus.com/pipermail/usrp-users_lists.ettus.com/2015-January/012269.html
<http://lists.ettus.com/pipermail/usrp-users_lists.ettus.com/2015-January/012269.html>
Any ideas why we might be seeing these spikes or what
we could do about it? Does the fix suggested in the
above mailing list post still apply to the current
codebase?
Thanks,
Thomas
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--
K. Steven Knudsen, Ph.D., P.Eng.
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