Hi John,
LO Leakage in general has ALWAYS been a problem for us as well in general on the UBX. The WBX was fine, we migrated to the UBX quite early and had significant problems that really were never resolved. Most of the chatter revolved around being continuously in high power mode, but honestly was mostly discussions. Not sure if any actions came out as a result... Our only mitigation approach was offset tuning, which does work pretty well, although this caused us other problems that we had to deal with. > On April 19, 2018 at 1:32 PM "Stanley, John P. via USRP-users" > <usrp-users@lists.ettus.com> wrote: > > > I’ve run into an issue with TX LO leakage/DC offset that appears to > affect the “Rev. C” hardware version of the UBX-40 daughter cards. When > running without any calibration data, LO leakage power is in line with > expectations (i.e. about -50 to -45 dBm with 0 dB of RF gain). But if the > uhd_cal_tx_dc_offset routine is run, LO leakage actually gets significantly > *worse*. When running with the newly generated calibration data, the LO > leakage power can get 15-30 dB higher. This is in stark contrast to the > behavior seen in older “Ver. B” and “Ver. A” UBX-40 boards, which > consistently show a 15-20 dB reduction in LO leakage power. > > > > I’ve observed this behavior across all 3 Rev. C boards I have checked so > far, and I have been unable to reproduce it on any Ver. A or Ver. B boards. > I’ve tested different daughter cards across different N210 and N200 main > boards and eliminated the main boards as a contributing factor; the behavior > follows the stamped hardware revision on the UBX daughter cards. > > > > I’ve attached a couple signal analyzer screenshots to illustrate the > issue. All 4 screenshots come from a UBX-40 board at 0 dB of RF gain being > fed with zero-valued samples at 12.5 Msps. The “Ver. B” board goes from about > -47 dBm before calibration down to about -69 dBm after calibration. The “Rev. > C” board, on the other hand, goes from about -49 dBm before calibration UP to > almost -15 dBm after calibration. I’ve observed this general pattern of > behavior across at least 2 versions of UHD, though the attached data was > generated using UHD 3.11.0. > > > > Could this be a hardware design issue, a bad production run, or maybe a > UHD issue? Has anyone else run into this? > > Thanks, > > John > > _______________________________________________ > USRP-users mailing list > USRP-users@lists.ettus.com > http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com >
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