To add to Marcus' comments, it is fairly common for users to pad transmissions with zeros before and after to minimize the affects of transients.
Regards, Michael On Thu, Mar 22, 2018 at 4:26 AM, Brais Ares via USRP-users < usrp-users@lists.ettus.com> wrote: > Thank you Marcus once again, crystal clear now. > > 2018-03-21 16:17 GMT+01:00 Marcus D. Leech via USRP-users < > usrp-users@lists.ettus.com>: > >> 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>: >> >>> 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 >>> 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> 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> 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> 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 >>>>>> >>>>>> 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 >>>>>> >>>>>> _______________________________________________ >>>>>> USRP-users mailing list >>>>>> USRP-users@lists.ettus.com >>>>>> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com >>>>>> >>>>>> >>>>> >>>>> >>>>> -- >>>>> K. Steven Knudsen, Ph.D., P.Eng. >>>>> >>>> >>>> _______________________________________________ >>>> USRP-users mailing list >>>> USRP-users@lists.ettus.com >>>> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com >>>> >>>> >>> >>> _______________________________________________ >>> USRP-users mailing list >>> USRP-users@lists.ettus.com >>> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com >>> >>> >> >> >> >> >> _______________________________________________ >> USRP-users mailing >> listUSRP-users@lists.ettus.comhttp://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com >> >> >> >> _______________________________________________ >> USRP-users mailing list >> USRP-users@lists.ettus.com >> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com >> >> > > > -- > > [image: logo_170x100px.png] <http://www.gradiant.org/> > > Brais Ares Fernández > Investigador - Desarrollador | Área de Comunicaciones Avanzadas > Researcher - Developer | Advanced Communications Department > > Ph. 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