2017-08-17 18:30 GMT+02:00 Richard Wilbur richard.wilbur@gmail.com:
On Aug 16, 2017, at 23:28, "mike.valk@gmail.com" mike.valk@gmail.com wrote:
2017-08-17 1:01 GMT+02:00 Richard Wilbur richard.wilbur@gmail.com:
On Aug 15, 2017, at 23:31, Luke Kenneth Casson Leighton lkcl@lkcl.net wrote: if i just take *out* the ground intermediary traces that would do the trick of bringing the impedance back up, is that right?
Should be a major step in the right direction.
After thinking it through I have to agree. Each GND trace would become coupled with the diff pairs. Effectively creating a link between two pairs. Which we do not want.
How about the ground plane below the traces... That's a major stray capacitance and closer than the "narrow" surrounding GND traces?
The ground plane would be stray except we designed it into the single-ended and differential impedance. At this point it is integral to our differential microstrip geometry. (See my original post in the thread "HDMI High-Frequency Layout: Impedance".)
I'll read that again.
I guess we just need to make sure that no other GND loop crosses the HDMI plane. Perhaps create a barrier on the GND that follows the outer HDMI traces. To prevent unwanted GND loops