2017-12-12 9:33 GMT+01:00 Luke Kenneth Casson Leighton lkcl@lkcl.net:
On Tue, Dec 12, 2017 at 8:10 AM, mike.valk@gmail.com
so by doing this series of steps the inter-pair impedance changes from its (appx).... 110 ohms by virtue of the distance being 15mil to each pair and also to the keep-out area, down to something closer to 50 ohms by the time we get to the end of the set of 8 steps, by which point the inter-pair spacing is 5mil, as you have to have, because of the distance between the pads on the ESD and the JAE DC-3 HDMI connector.
if we followed the "straight line" inter-pair approach that you're advocating, the change from the 110 ohms to 50 ohms using linear spacing between 45-turn steps OR a straight 1-line arbitrary-angle taper is *GUARANTEED* to result in reflections back down the line(s).
We'll I'm not convinced on the reflections in inter pair matching. But indeed my "linear" might not be the best and results in unequal impedance transitions and thus in signal degradation. But you can stil do gradual corners. See the "transitioned" attachment.
But without a, 3d, simulation or a real world test this is all very theoretical.
btw numbers (110, 50) above are not wholly accurate, richard calculated them correctly, i am just substituting convenient indicative numbers from my vague and non-specific memory.
l.
arm-netbook mailing list arm-netbook@lists.phcomp.co.uk http://lists.phcomp.co.uk/mailman/listinfo/arm-netbook Send large attachments to arm-netbook@files.phcomp.co.uk
