[SI-LIST] Re: Should the signals always return back through GND

  • From: steve weir <weirsi@xxxxxxxxxx>
  • To: nikitanivan@xxxxxxxxxxx, si-list@xxxxxxxxxxxxx
  • Date: Mon, 22 Aug 2005 07:57:56 -0700

Nikita, good question.

No, signals don't know or care about "ground".  Dr. Archambeault likes to 
say that "ground" is a place for potatoes and carrots to grow.  EM waves, 
which is what our signals are, care about wave guides, good or bad.

Signals and their returns are the two edges of one wave front.  They 
SIMULTANEOUSLY propagate away from the source bouncing between any 
reflection boundaries ( metal ) that they encounter.  If the nearest chunk 
of metal happens to be a 480V main, an isolated plate, or a plane tied to 
Vss, it is all the same to the wave front.  This is just the same as 
tossing a stone in a pool of water.  The waves propagate outward reflecting 
off the pool boundaries.

Steve.


At 03:40 PM 8/22/2005 +0100, Nikita nivan wrote:
>Hi SI virtuosi,
>
>I am new to this group and to this field too.I have a
>doubt thats buzzing my mind.I know you people
>could help me out. My question is
>
>Its always said that GND acts as a return path for a
>signal.Do all the signals know that they
>have to return back through GND and not through
>anyother track in the signal layer having
>lower impedance? What are the factors taken into
>consideration to make sure that signals return
>back through GND.
>
>Waiting for your reply
>
>Thanks in advance,
>Nikita
>
>
>
>
>
>
>
>
>
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