On 2015-06-25 12:02 PM, Noel Chiappa wrote:
> From: John Wilson
> I chose the digital version of EE as my major precisely because I knew
> I'd flunk Fields and Waves. Transmission lines are black magic as far
> as I'm concerned!
I too have a hard time with analog in general, but transmission lines I seem
to be OK with.
The way I think about them is to model them as pipes, and the signal as a
sound (single pulse) sent down the pipe. Proper termination is like a piece
of cotton at the end of the pipe, it sucks up the sound and you don't get a
reflection. If you just cap off the end of the pipe (i.e. no termination),
the sound bounces, and you get an echo.
So if you have a small un-terminated branch, part of the pulse bounces off
the end, and comes back out, and then propogates both ways, so the original
pulse gets a messy trailer tacked on the back of it. Etc, etc.
I dunno how accurate this model of mine is, but it seems to work OK! :-)
For the YouTube generation - there's Dr John Shive's 1959 video:
https://www.youtube.com/watch?v=DovunOxlY1k
Note, there's an intro of 1 min 20 seconds.
--Toby
Noel
