[SI-LIST] Re: Transmission Line

Hi Jim,
Can we use EM wave theory to explain this phenomena, i.e.
part of EM wave will be reflected when it reachs the discontinue
dielectric matrial ?

Shulong

Jim Antonellis wrote:

> You may luck out and someone with a lot of free time on their
> hands may provide you with a more detailed answer and/or more
> pointers to docs.... I on the otherhand offer you the following:
>
> 1- A very brief, very vague, high level explanation of "the physics":
>
>         Given a signal transmission from point A (tx) to point B (rx)
>         over a channel C (e.g. PCB trace), any energy that is not lost
>         in the channel due to channel losses will arrive at point B
>         and depending on the impedance of point B (Zb) relative to the
>         channel impedance (Zc) the energy will either be: fully absorbed
>         IFF Zb == Zc, or, some amount of energy will be reflected due to
>         a mismatch of channel impedance and RX impedance (i.e. Zc != Zb);
>         A reflection coeffecient calculates the amount of reflected enrgy.
>         I've taken many liberties in this simple description and hence I
>         move to option 2...
>
> 2- Respectful advice:
>
>         Please spend a good amount of time reading the vast volumes of
>         excellent information on Transmission line theory available in
>         text books and application notes on the web.
>
>         If you search the si-list archives you will find many recommended
>         text books on the subject. You can't go wrong with either of the
>         Johnson and Graham texts off the top of my head.
>
> Regards,
> Jim
>
> -
> Jim Antonellis   janton@xxxxxxxxxxxxx
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> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx
> [mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of pomgud
> Sent: Wednesday, March 23, 2005 5:25 AM
> To: si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Transmission Line
>
> Hello Guys
>  I have one doubt about transmission line basic fundamental. I know
> that there are reflections on transmission line if there is a
> impedance mismatch. I would like know how the reflections are
> generated if there is a impedence mismatch. What is the physics
> behind this phenomena?
> Thanks in advance
> bye
>
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