Hi Dan, The E310/E312 has the switchable set of receive and transmit filters which the B2xx does not. This will impact the noise figure due to the additional losses of the switches and filters. As with most receivers an external LNA and filter matched to a frequency of interest will reduce the total system noise figure.
Derek On Sun, Feb 4, 2018 at 5:55 PM, Dan CaJacob via USRP-users < usrp-users@lists.ettus.com> wrote: > Yep, I am aware of that document and I am using the Y-factor method. > > The 3 dB attenuator was calibrated with the B200 - i.e. I measured the NF > of the USRP + 3dB attenuator as a system. That data then serves as the > calibration data to correct for it's contribution to the subsequent NF > measurement of the B200 + 3dB pad + DUT. > > I saw the same poor performance below 1 GHz when using the 3dB pad. > > On Sun, Feb 4, 2018 at 11:44 AM David Bengtson <david.bengt...@gmail.com> > wrote: > >> A 3dB attenuation will really improve the reflection coefficient. >> Using this calculator >> http://www.rfcafe.com/references/calculators/vswr-return-loss-conversion- >> calculator.htm >> you can see that a 3 dB attenuation will improve a 3:1 VSWR to 1.7:2, >> or a 6 dB return loss to 12 dB, so you've really improved the match. >> The gory details of noise figure and match are in here >> http://literature.cdn.keysight.com/litweb/pdf/5952-3706E.pdf and >> Keysight has a spreadsheet to do the calculations here >> https://www.keysight.com/main/editorial.jspx?cc=US&lc=eng&; >> ckey=96887&nid=-34815.0.00&id=96887 >> (Probably more detail than needed) >> >> Did you add the 3dB attenuator to the noise figure? >> >> Dave >> >> >> >> On Sat, Feb 3, 2018 at 10:41 AM, Dan CaJacob via USRP-users >> <usrp-users@lists.ettus.com> wrote: >> > I saw no improvement when including a 3dB 50 Ohm attenuator as part of >> the >> > B200 NF meter. I guess I could try higher attenuator values. >> > >> > On Thu, Feb 1, 2018 at 9:16 PM Dan CaJacob <dan.caja...@gmail.com> >> wrote: >> >> >> >> I was gonna say, there's actually three of them ;) >> >> >> >> >> >> On Thu, Feb 1, 2018, 9:06 PM Robin Coxe via USRP-users >> >> <usrp-users@lists.ettus.com> wrote: >> >>> >> >>> On p.8 of B200 schematic: >> >>> T801 is Macom ETC1-1-13TR (RF2) >> >>> T800 is Minicircuits TC1-1-43A+ (RF3) >> >>> U802 is Anaren BD3150L50100AHF (RF1) >> >>> >> >>> On Thu, Feb 1, 2018 at 5:45 PM, Ron Economos via USRP-users >> >>> <usrp-users@lists.ettus.com> wrote: >> >>>> >> >>>> There's also a balun on the AD9361 input. Unfortunately, the balun >> part >> >>>> number for the low frequency path is not on the schematic. >> >>>> >> >>>> Ron >> >>>> >> >>>> On 02/01/2018 05:39 PM, Dan CaJacob via USRP-users wrote: >> >>>> >> >>>> That's an interesting thought. The 9361 does have a pretty bad match. >> >>>> I'll try adding a 50 Ohm attenuator and see if that helps. >> >>>> >> >>>> On Thu, Feb 1, 2018 at 5:14 PM Robin Coxe <robin.c...@ettus.com> >> wrote: >> >>>>> >> >>>>> Hi Dan. Both the B200 and the E312 use the Analog Devices AD9361 >> RF >> >>>>> integrated transceiver. This chip does have an integrated LNA. >> Perhaps >> >>>>> there's some sort of mismatch between your DUTs and this integrated >> LNA at >> >>>>> <1 GHz? >> >>>>> >> >>>>> ADI publishes the RX S-parameters: >> >>>>> https://ez.analog.com/thread/41208#137929 >> >>>>> >> >>>>> -Robin >> >>>>> >> >>>>> On Thu, Feb 1, 2018 at 7:46 AM, Dan CaJacob via USRP-users >> >>>>> <usrp-users@lists.ettus.com> wrote: >> >>>>>> >> >>>>>> Hey guys, >> >>>>>> >> >>>>>> I have put together a noise figure meter application that uses a >> USRP >> >>>>>> as the sensing device. It started off as a way to measure the NF >> of the USRP >> >>>>>> itself. I have a calibrated noise source from an HP 8970B Noise >> Figure >> >>>>>> Meter. To test the NF of the USRP, I connect the head to the USRP >> input. My >> >>>>>> GNURadio flowgraph maximizes the USRP gain and measures a moving >> average of >> >>>>>> the received power while I switch the noise source on and off. The >> >>>>>> difference in the received power level, in addition to the ENR >> table from >> >>>>>> the noise source, can then be used to calculate the NF of the USRP >> itself >> >>>>>> using the y-factor method. >> >>>>>> >> >>>>>> Once you have the NF for the USRP at many frequencies (I test >> every 50 >> >>>>>> MHz from 50 MHz - 6000 MHz), you can modify the same procedure to >> test the >> >>>>>> NF of a Device Under Test (DUT) which is connected between the >> noise source >> >>>>>> and the (now calibrated) USRP. You can use the USRP cal table we >> generated >> >>>>>> in the previous step to derive the NF of the DUT corrected for the >> NF of the >> >>>>>> USRP. >> >>>>>> >> >>>>>> In short, this all works incredibly well and garners very >> repeatable >> >>>>>> results. One complication is that you will see wild NF at certain >> >>>>>> frequencies due to local interference like LTE and WIFI. I've also >> compared >> >>>>>> the results to that which the HP device measures and they're very >> >>>>>> comparable. ... Except below ~ 1GHz. >> >>>>>> >> >>>>>> And here's the issue - I am seeing higher NF for DUTs below about >> 1GHz >> >>>>>> and particularly worse below 500 MHz. I was hoping someone at >> Ettus might be >> >>>>>> able to shed some light on why this might be. Curiously, the USRPs >> NF >> >>>>>> doesn't seem to be too bad, just the DUT. >> >>>>>> >> >>>>>> I'll note that I am nominally using a B200 for these tests, but I >> also >> >>>>>> tried an E312 just in case the filter banks might help out >> somehow. I didn't >> >>>>>> see a difference - they both had the same problem. >> >>>>>> >> >>>>>> I have used several DUTs for this test, including LNA boards we >> have >> >>>>>> designed ourselves and a Mini-Circuits ZX60-P103LN+ >> >>>>>> (https://www.minicircuits.com/pdfs/ZX60-P103LN+.pdf). Both seem >> to exhibit >> >>>>>> higher NF when measured with a USRP below 1 GHz. When testing them >> on the HP >> >>>>>> NF meter, the NF is as expected all the way down to 50 MHz. >> >>>>>> >> >>>>>> I have attached the B200 cal data for your enjoyment as well as the >> >>>>>> B200-measured ZX60 NF and the HP-measured ZX60. The HP NF meter >> only goes up >> >>>>>> to 1600 MHz, which is why that data file stops there. I was >> surprised to see >> >>>>>> the B200 seemed to have a better NF than the E312, which averaged >> 8 dB NF, >> >>>>>> by the way. >> >>>>>> -- >> >>>>>> Very Respectfully, >> >>>>>> >> >>>>>> Dan CaJacob >> >>>>>> >> >>>>>> _______________________________________________ >> >>>>>> USRP-users mailing list >> >>>>>> USRP-users@lists.ettus.com >> >>>>>> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com >> >>>>>> >> >>>>> >> >>>> -- >> >>>> Very Respectfully, >> >>>> >> >>>> Dan CaJacob >> >>>> >> >>>> >> >>>> _______________________________________________ >> >>>> 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 list >> >>> USRP-users@lists.ettus.com >> >>> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com >> >> >> >> >> >> >> >> -- >> >> Very Respectfully, >> >> >> >> Dan CaJacob >> > >> > -- >> > Very Respectfully, >> > >> > Dan CaJacob >> > >> > _______________________________________________ >> > USRP-users mailing list >> > USRP-users@lists.ettus.com >> > http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com >> > >> > -- > Very Respectfully, > > Dan CaJacob > > _______________________________________________ > USRP-users mailing list > USRP-users@lists.ettus.com > http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com > >
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