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Bug #3775

properly debug limesdr usb and limesdr mini clocking requirements and osmo-trx support

Added by roh 3 months ago. Updated 2 months ago.

Status:
In Progress
Priority:
Normal
Assignee:
Category:
LimeSDR
Target version:
-
Start date:
01/31/2019
Due date:
% Done:

20%

Spec Reference:

Description

limesdr usb and limesdr mini need a external reference clock to be used for gsm applications properly since the internal oscillator is sadly not of the required performance class.

limesdr usb has an extra internal pll (ADF4002 and Si5351C as well as LMK00105) and can handle different external clocks quite flexible
limesdr mini has no pll chip, but only a clock buffer (LMK00105) and needed some help from the fpga to make clocks possible which are not 40MHz

lms_mini_clock_in_50ohm.png View lms_mini_clock_in_50ohm.png 12.7 KB roh, 01/31/2019 05:29 PM
lms_mini_clock_in.png View lms_mini_clock_in.png 13.4 KB roh, 01/31/2019 05:29 PM
lms_mini_clock_out.png View lms_mini_clock_out.png 12.1 KB roh, 01/31/2019 05:29 PM
lms_mini_clock_out_50ohm.png View lms_mini_clock_out_50ohm.png 11.9 KB roh, 01/31/2019 05:29 PM
gpsdo_50ohm.png View gpsdo_50ohm.png 11.6 KB roh, 01/31/2019 05:52 PM
gpsdo.png View gpsdo.png 13.9 KB roh, 01/31/2019 05:52 PM
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Related issues

Blocks OsmoTRX - Bug #3341: osmo-trx-lms RF Envelope FAIL on LimeSDR, but not on LimeSDR-miniIn Progress2018-06-13

Blocks OsmoTRX - Bug #3342: osmo-trx-lms: low tx output power levelIn Progress2018-06-13

Blocked by OsmoTRX - Bug #3861: fix function call ordering to support LimeSuite 19.01In Progress2019-03-25

History

#1 Updated by roh 3 months ago

there is https://github.com/myriadrf/LimeSuite/issues/244 to get more details about the required clock specifications and documentation from lime

#2 Updated by roh 3 months ago

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looking at the schematic, i think there should be proper termination for 50Ohm, but i see a lot of ringing on the input which i do not see not there when i only connect the gpsdo to a 50ohm terminated scope input.
the screenshots for the input are done with a bnc-t inbetween the gpsdo and the mini, the output ones are directly connected to the mini.

#3 Updated by roh 3 months ago

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gpsdo slope for reference - without and with 50ohm termination.

#4 Updated by roh 3 months ago

  • Status changed from New to In Progress

#5 Updated by roh 2 months ago

  • Blocks Bug #3341: osmo-trx-lms RF Envelope FAIL on LimeSDR, but not on LimeSDR-mini added

#6 Updated by roh 2 months ago

  • Blocks Bug #3342: osmo-trx-lms: low tx output power level added

#7 Updated by roh 2 months ago

  • % Done changed from 10 to 20

i repeated the experiments today with a 'clock converter' based on ltc6957-4 with 40MHz, still usin limesuite 18.10.

sadly i could not get the dcs1800 band to have better results than with the 10MHz square clock from the gpsdo last time.

phase-noise is still way too high for a 'PASS' result (needs to be <5° rms and ~<10° pk) (check phase shots of #3341 and #3342)

next experiment is to use a clock generator based on si5351c

#8 Updated by roh 4 days ago

  • Blocked by Bug #3861: fix function call ordering to support LimeSuite 19.01 added

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