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Andrey Sviyazov andrey.sviyazov at fairwaves.ruHi Thomas. First of all thank you very much. And of course few questions: 1 why you use too small input signal to the analyser? I saw -120dBc/Hz @ 1MHz offset. 2 do you test LO with small CP current? 3 I don't see now noise peak @ 30kHz. Do you change something? 4 can 4406 measuring noise plot with log freq? 5 what type of modulation you use now? I mean 1 sps or 2? Best regards, Andrey Sviyazov. (Sent from my mobile client) 21.07.2012 0:23 пользователь "Thomas Tsou" <thomastsou at gmail.com> написал: > On Fri, Jul 20, 2012 at 1:14 PM, Andrey Sviyazov > <andrey.sviyazov at fairwaves.ru> wrote: > > Hi Thomas. > > > > I couldn't wait your reply and start to implement 10kHz BW of PLL. > > You can find here two pictures with results. > > First of all I found that PLL tuning algorithm doesn't work properly at > low > > PLL BW. > > VCOCAP register (r0x19) should contain higher value at least for +3 units > > (to make CAP lower), otherwise freq's above 950MHz never locked. > > Note, that you should read and change register 0x19 after autotuning. > > Second, you can see some noise difference for the 925MHz because of used > > DIV=8 of the VCO, instead of DIV=4 for 942 and 960MHz. > > Third, you can see PLL noice dependance with the charge pump current > > (r0x16). > > > > On the other two pictures you can find which components have to be > changed. > > Thomas, please make one more measure of LO noise and jitter at PLL > BW=10kHz > > by your instrument. > > We need to know, is it real to reach modulation accuracy of 1.5 degrees > RMS > > or impossible, just because of LMS PLL have bigger jitter. > > Here are phase noise plots with following settings measured at 925 MHz > and 945 MHz. > > --reg 0x16 --data 0x93 > --reg 0x26 --data 0x98 > > Charge pump current had a definite effect as did changing the > frequency. Measured on the E4406A, phase error is quite high. There > are still other calibration issues, but phase noise is probably still > a concern. I also still have errors with auto calibration. > > Note that USRP1 - with better phase noise - does not reach < 1.5 > degree error, but is close at < 2.0 degrees RMS. > > I'm currently going through the previous issues. If there is anything > else I should examine or test, let me know. > > Thomas > -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.osmocom.org/pipermail/umtrx/attachments/20120721/5d5c5779/attachment-0001.htm>