[Arm-netbook] HDMI High-Frequency Layout: Recommendations--Taper

[Luke Kenneth Casson Leighton]

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crowd-funded eco-conscious hardware: https://www.crowdsupply.com/eoma68


On Tue, Dec 5, 2017 at 12:41 PM, Luke Kenneth Casson Leighton
<lkcl at lkcl.net> wrote:
> On Tue, Dec 5, 2017 at 12:30 AM, Richard Wilbur
> <richard.wilbur at gmail.com> wrote:
>
>> 3.  Reflections are more troublesome the further you get from the
>> signal source.  Close to the source the reflection arrives at the
>>  source during the signal rise time and can be overcome by the line driver.
>
>> Deviations from path in due NorthEast direction (+ signifies change in the
>> NorthWest direction, - signifies change in the SouthEast direction, units in mil)
>> <step>  <Northern keepout> <TX1> <TX0> <TXC> <Southern keepout>
>> 0     0  0  0  0  0
>> 1     -1  1  2  3  4
>> 2     -1  1  2  3  4
>> 3     -1  1  2  3  4
>> 4     -2  2  4  6  8
>> 5     -2  2  4  6  8
>> 6     -1  1  2  3  4
>> 7     -1  1  2  3  4
>> 8     -1  1  2  3  4
>
>   okaay so the idea is, just after the long straight you make a series
> of very tiny corrections by bringing each of the tracks inwards -
> closer together - so that when you get to the point where you *have*
> to be 5-7mil apart you're already neeearrrrly that far apart *anyway*
> so it's not so bad.
>
>  ok :)  that's perfectly doable.

so, a quick check: it's easier, due to the VIAs (i am *not* moving
them!! certainly not the diff-pairs!) to keep TX1 exactly where it is,
and move TX2, TX0 and TXC all inwards.  i'll also move the last change
from N to NE that goes round the GND via a bit closer in.

question: does it *really matter* that the tapering occurs after the
45 degree group turn or is it ok to simply... ok picture 1 or picture
2? :)

thoughts appreciated
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