[SI-LIST] Re: Fw: si-list Digest V7 #410

Ria,

On passivity for linear networks in the freq. domain: matrix A=1-S'S must
be semidefinite positive (A>=0), where '=hermitian conjugate. For a 2 port
network, A11>0 A22>0 and det(A)>0. Otherwise, network is not passive
(either lossless (=0) or active(<0)).

Regards,
Luciano
UMass, Lowell

> Ria,
> I'll take a stab it this.
>
> Passivity - a passive network that has no external power cannot add energy
> to a signal.  If you look at amplitude vs. frequency for a passive network
> (e.g. s21 parameter), it should never go above one.  I believe the math is
> more complicated than that, but this is the general idea.  Anybody care to
> elaborate?
>
> Causality - a signal cannot traverse any transmission medium faster than
> the speed of light in that medium.  This term comes from relativity where
> event A cannot cause event B unless it happens before event B.
>
> Besides nonphysical simulation results, models that have these problems
> can also give simulators numerical trouble.
>
> Has anyone on the list seen a set of publicly available canned routines
> for evaluating causality and passivity of s-parameters?
>
> Greg
>
> Greg Edlund
> Senior Engineer
> Signal Integrity
> IBM Global Engineering Solutions
> 3605 Hwy. 52 N, Dept. HDC
> Rochester, MN 55901
> gedlund@xxxxxxxxxx
>
> ----- Forwarded by Gregory R Edlund/Rochester/IBM on 12/07/2007 08:00 AM
> -----
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> Subject
> si-list Digest V7 #410
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>
> si-list Digest           Fri, 07 Dec 2007                Volume: 07 Issue:
> 410
>
> In This Issue:
>                  #1:             From: Ria R <ria_rr_84@xxxxxxxxx>
>                                  Subject: [SI-LIST] Passivity/Causality
>
> ----------------------------------------------------------------------
>
> Msg: #1 in digest
> Date: Thu, 6 Dec 2007 21:58:24 -0800 (PST)
> From: Ria R <ria_rr_84@xxxxxxxxx>
> Subject: [SI-LIST] Passivity/Causality
>
> Gurus,
>   I have heard these 2 terms alot in the world of SI: Passivity and
> Causality.
>   I tried googling it and I dont seem to get what I am lookimg for.
>  Can someone please throw some light on the definitions of these 2 terms
> and what significance they have in Signal Integrity?
> Thanks in advance,
> Best Regards,
>
> Ria.
>
>
>
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Regards,
Luciano Boglione, PhD
---------------------------
mailto: l.boglione@xxxxxxxx

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