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

[Richard Wilbur]

On Wed, Jan 3, 2018 at 9:53 PM, Luke Kenneth Casson Leighton
<lkcl at lkcl.net> wrote:
> On Thu, Jan 4, 2018 at 12:22 AM, Richard Wilbur
> <richard.wilbur at gmail.com> wrote:
>
>> My initial feedback is it looks pretty nice.  I sat down, read the documentation
>> for the gerber viewer that comes with KiCAD and started getting my feet wet.
>
>  good god.  you read documentation?? :)

I scanned it fairly quickly to get a good idea of how to interact with
the program.  That way I had some idea what the icons meant and what
functions were available in the user interface.  (Okay, I've written
documentation before so I figured since it was available I'd look it
over.  It gave me a pretty quick idea of how the user interactions are
structured.)

>> One recommendation for now as I have to leave for choir rehearsal--do
>>  the same thing with additional ground traces north and south of the ESD
>> pads on layer 6 as you did on layer 1 to bring the distance between pad
>> and ground down from 15mil to around the same as the pad-to-pad spacing
>> of the ESD component pads.
>
>  yep sorted.  will send you new gerber set, for anyone else to see
> (and also make it easier for you, richard) attached screenshot.

Beautiful!

I think that was the most important change I noticed.  I am mainly
looking at the HDMI which we have been laboring over the last few
months.

My next suggestion has an associated question:

I notice that north of the long east-west transmission line, at the
northern keepout boundary on layer 6, there are a couple of vias that
have almost complete ground shield between the vias and the HDMI TX2
pair.

Question:  What is the fill polygon width for ground fill on layer 6?

I can see two fairly simple solutions to complete the ground shield
around these vias:
1.  Add traces to complete the ground shield between vias and HDMI
differential pair.
2.  Adjust trace/fill polygon width for ground fill on layer 6 till
the ground shield is complete.

I'll sleep on it and take another look tomorrow morning.