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Srdjan Milenkovic s.milenkovic at limemicro.comHi Andrey, Below is the loop filter for 100kHz loop bandwidth, 26MHz reference clock, 400uA charge pump current. It has been tested and should give you around -90dBc/Hz plateau. C1 R2 C2 R3 C3 9.01E-11 2.46E+03 1.42E-09 3280.93 2.56E-11 Loop filter components for 10kHz bandwidth, 26MHz reference clock, 400uA charge pump current are below: C1 R2 C2 R3 C3 9.01E-09 2.46E+02 1.42E-07 328.09 2.56E-09 There should not be any issue with loop stability even with 10kHz filter. However, PLL settling time is increased so you have to slow down VCOCAP auto-tune. I would recommend to use 100kHz filter. Regards, Srdjan On 22/07/2012 20:53, Andrey Sviyazov wrote: > Hi Srdjan. > > First of all thank you for support. > > We do not have register dump. However, Lime GUI project file used > in this experiment is attached. You can use GUI File->Open Project > option to import it. I see Ichp and Ichp offset currents are > different from defaults but these still do not justify 5-12dB > worse PN in your reports. You can give it a try though before > changing TCXCO. > > > We will try to adjust Ichp and offset first off all. Thank you for hint. > > *Test Description:* > > * DC MAX applied through analogue inputs, DACs off > > It is quite important detail too. > > * TXVGA1 and TXVGA2 at max gain > > Similar. > > * Loop filter redesigned for 100kHz loop bandwidth and 40MHz > reference > > * Icp and Icp offset optimized at 25 deg. Same set up used at > all other temperatures > > Please inform us values of components for 100kHz BW filter. > But we are forced to use one clock 26MHz for all because of target price. > > * Cap code and VCO picked up by PLL tune routine > > I implemented 10kHz BW filter for PLL and found that frequency locking > become unstable because of calculated VCOCAP value a bit lower then > required (too high capacity). > If VCOCAP incremented manualy (after auto-tuned) then no any problems. > What do you think about it. > And could you please inform me values for 10 kHz BW filter, just to > compare with my calculations. > > Best regards, > Andrey Sviyazov. > > -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.osmocom.org/pipermail/umtrx/attachments/20120723/95377e7d/attachment.htm> -------------- next part -------------- A non-text attachment was scrubbed... Name: adibgfic.png Type: image/png Size: 7290 bytes Desc: not available URL: <http://lists.osmocom.org/pipermail/umtrx/attachments/20120723/95377e7d/attachment.png>