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 >>> 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 >>> >>> >> _______________________________________________ >> 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
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