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Thomas Tsou thomastsou at gmail.comOn 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 -------------- [ttsou at ovid utils (umtrx)]$ ./umtrx_lms.py --lms 1 --lms-init [ttsou at ovid utils (umtrx)]$ ./umtrx_lms.py --lms 1 --lms-tx-enable 1 [ttsou at ovid utils (umtrx)]$ ./umtrx_lms.py --lms 1 --reg 0x34 --data 0x3e [ttsou at ovid utils (umtrx)]$ ./umtrx_lms.py --lms 1 --pll-ref-clock 26e6 --lpf-bandwidth-code 0x0f --lms-auto-calibration LPF Tuning... DC_REGVAL = 31 LPF Bandwidth Tuning... FREQSEL=47 VCO_X=16 NINT=196 NFRACK=7743330 VOVCO[0]=2 VOVCO[1]=2 VOVCO[2]=2 VOVCO[3]=2 VOVCO[4]=2 VOVCO[5]=2 VOVCO[6]=2 VOVCO[7]=2 VOVCO[8]=2 VOVCO[9]=2 VOVCO[10]=2 VOVCO[11]=2 VOVCO[12]=2 VOVCO[13]=2 VOVCO[14]=2 VOVCO[15]=2 VOVCO[16]=2 VOVCO[17]=2 VOVCO[18]=2 VOVCO[19]=2 VOVCO[20]=2 VOVCO[21]=2 VOVCO[22]=2 VOVCO[23]=2 VOVCO[24]=2 VOVCO[25]=2 VOVCO[26]=2 VOVCO[27]=2 VOVCO[28]=2 VOVCO[29]=2 VOVCO[30]=2 VOVCO[31]=2 VOVCO[32]=2 VOVCO[33]=2 VOVCO[34]=2 VOVCO[35]=2 VOVCO[36]=2 VOVCO[37]=2 VOVCO[38]=2 VOVCO[39]=2 VOVCO[40]=2 VOVCO[41]=0 Norm VOVCO[42]=0 VOVCO[43]=0 VOVCO[44]=0 VOVCO[45]=0 VOVCO[46]=0 VOVCO[47]=0 VOVCO[48]=0 VOVCO[49]=0 VOVCO[50]=0 VOVCO[51]=0 VOVCO[52]=1 Low VOVCO[53]=1 VOVCO[54]=1 VOVCO[55]=1 VOVCO[56]=1 VOVCO[57]=1 VOVCO[58]=1 VOVCO[59]=1 VOVCO[60]=1 VOVCO[61]=1 VOVCO[62]=1 VOVCO[63]=1 START=41 STOP=51 SET=46 code = f f f RCCAL = 7 Tx LPF DC calibration... DC_REGVAL = 33 DC_REGVAL = 33 Rx LPF DC calibration... Error: DC Offset Calibration does not converge! RxVGA2 DC calibration... Error: DC Offset Calibration does not converge! [ttsouu at ovid utils (umtrx)]$ -------------- next part -------------- A non-text attachment was scrubbed... Name: usrp1_52_phs_noise.PNG Type: image/png Size: 74575 bytes Desc: not available URL: <http://lists.osmocom.org/pipermail/umtrx/attachments/20120720/926b29b7/attachment-0003.png> -------------- next part -------------- A non-text attachment was scrubbed... Name: umtrx_phs_noise_925.PNG Type: image/png Size: 74696 bytes Desc: not available URL: <http://lists.osmocom.org/pipermail/umtrx/attachments/20120720/926b29b7/attachment-0004.png> -------------- next part -------------- A non-text attachment was scrubbed... Name: umtrx_phs_noise_945.PNG Type: image/png Size: 74751 bytes Desc: not available URL: <http://lists.osmocom.org/pipermail/umtrx/attachments/20120720/926b29b7/attachment-0005.png> -------------- next part -------------- A non-text attachment was scrubbed... Name: screen4.bmp Type: image/bmp Size: 70460 bytes Desc: not available URL: <http://lists.osmocom.org/pipermail/umtrx/attachments/20120720/926b29b7/attachment-0001.bin>