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New ECN about clock circuit of atusd boards. Measured (absence of) effect of

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adding an inductor to the clock line.

- ecn/INDEX, ecn/ecn0005.txt: new ECN discussing the switch to a
  capacitative clock voltage divider. With frequency measurements.
- atusd/tests/send-20100910: measurement of transceiver performance when
  placing an inductor in the 16 MHz clock line.
This commit is contained in:
Werner Almesberger
2010-09-10 00:06:33 -03:00
parent d3bc274dab
commit df071c3398
3 changed files with 104 additions and 0 deletions
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atusd/tests/send-20100910
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Same test setup as for send-20100909. Board 100908-A was modified to have
a 220 nH inductor in the C7 position, instead of a 0R resistor.
Distant Local
--------------- --------------- ---------------
100813-red 100813-orange 100908-A (with inductor)
TX 255, -91 255, -85
TX 255, -90 255, -85
TX 255, -91 -
TX 255, -90 255, -85
TX 255, -91 garbled
- TX 255, -47
- TX 255, -47
- TX 255, -47
- TX 255, -47
garbled (-90) TX 255, -47
255, -82 255, -43 TX
255, -82 255, -43 TX
255, -82 255, -43 TX
255, -82 255, -43 TX
255, -82 255, -43 TX
Control experiment:
100813-red 100813-orange 100908-B (unmodified)
TX - 255, -83
TX garbled (-91) 255, -86
TX - 255, -86
TX garbled (-91) 255, -86
TX - 255, -86
255, -83 255, -43 TX
255, -84 255, -43 TX
255, -85 255, -43 TX
255, -84 255, -43 TX
255, -84 255, -43 TX
Summary
-------
Direction No inductor (1) With ind. (2) Change
------------------------------- --------------- ------------ ------
100813-red -> 100813-orange 255, -87 255, -91 -4 dB
100813-red -> 100908-A 255, -88 255, -85 +3 dB
100908-A -> 100813-red 255, -85 255, -82 +3 dB
100813-red -> 100813-orange 255, -90 - ?
100813-red -> 100908-B 255, -90 255, -86 +4 dB
100908-B -> 100813-red 255, -87 255, -84 +3 dB
(1) Data from send-20100909
(2) Only 100908-A was modified. Changes in the measurements with
100908-B show inaccuracies of the test setup.
Conclusion
----------
The differences observed are the same for the modified 100908-A board
and the unmodified 100908-B board. The inductor therefore does not seem
to have a significant effect on transceiver performance.