fast pulse on ribbon cable

jlarkin · 2021-05-23T00:36:43+00:00

I want to send a fast trigger pulse a short distance inside arackmount enclosure, a foot or two between boards. Signals will bepretty fast differential PECL, maybe 120 ps edges.The usual ribbon cable config would beg g P N g g (maybe 120 ohms diff impedance)namely a differential pair with surrounding grounds.But one could also dog g P g N g g org g P g g N g g (about 80 ohms per wire, 160 diff)or eveng g P P g g N N g g (who knows?)Maybe some would have lower losses than the first one.Regular IDC ribbon cables are nice. CAT6 would be clumsy, and theLemo/Fisher connectors are too expensive and fussy.

May 23, 2021 Last reply: 5 years ago 22 Replies

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Joerg 5 years ago

I have used Parlex cable for up to 5GHz and in our case that was (IIRC) a 20ft length. Standard lengths with the ends prepared for connector insertion go up to 27" AFAIR.

Looks like this, comes in various numbers of lines and the ends slide into a connector that then "grips" them:

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This stuff seems indestructable and you could probably pull out a small tree stump with it.

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whit3rd 5 years ago

[about a fast edge transmission]

Thin coax is nicer. Semirigid is nicer still, if you really care about dispersion. Twisted pairs are convenient, but those RJ45 connectors are not the greatest transmission line terminations... Sharing a cable with a potentially noisy power supply doesn't seem wise. There's modulated load current on power lines.

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