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Bug #3775

open

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

Added by roh almost 3 years ago. Updated about 1 year ago.

Status:
Stalled
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


Files

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

Related issues

Blocks OsmoTRX - Bug #3341: osmo-trx-lms RF Envelope FAIL on LimeSDR, but not on LimeSDR-miniStalled06/13/2018

Actions
Blocks OsmoTRX - Bug #3342: osmo-trx-lms: low tx output power levelStalledHoernchen06/13/2018

Actions
Blocked by OsmoTRX - Bug #3861: fix function call ordering to support LimeSuite 19.01Resolvedsysmocom03/25/2019

Actions
Actions #1

Updated by roh almost 3 years ago

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

Actions #2

Updated by roh almost 3 years ago

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.

Actions #3

Updated by roh almost 3 years ago

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

Actions #4

Updated by roh almost 3 years ago

  • Status changed from New to In Progress
Actions #5

Updated by roh almost 3 years ago

  • Blocks Bug #3341: osmo-trx-lms RF Envelope FAIL on LimeSDR, but not on LimeSDR-mini added
Actions #6

Updated by roh almost 3 years ago

  • Blocks Bug #3342: osmo-trx-lms: low tx output power level added
Actions #7

Updated by roh almost 3 years 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

Actions #8

Updated by roh over 2 years ago

  • Blocked by Bug #3861: fix function call ordering to support LimeSuite 19.01 added
Actions #9

Updated by roh over 2 years ago

the spec from the clockchip used (ti LMK00105) speaks of "sharp rectangles 2V/ns or better".

Actions #10

Updated by laforge about 1 year ago

  • Assignee deleted (roh)
Actions #11

Updated by laforge about 1 year ago

  • Status changed from In Progress to Stalled
Actions

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