Bottom line is, Alastair has a legitimate question concerning frequency
dependent material properties in transmission lines which is relevant to
practical situations.
I don't know of any analytical code that can handle this problem directly
and produce a time domain model although one can certainly solve the problem
at a number of discrete frequencies to create a freqeuncy domain model.
Some SPICE codes allow one to input tabular frequency domain data and then
do a time domain simulation.
I hope this is helpful. (...and if anyone has any kovar permeability data
vs frequency, please let me know)
---------------------------------------------------------------
Eric Wheatley Ph.D. (760) 942-9426 (phone)
Alterra Technology Co. (760) 942-2366 (fax)
Encinitas, CA 92024 alterra@adnc.com
---------------------------------------------------------------
At 04:07 PM 9/18/97 -0700, HANS_MELLBERG@NON-HP-Cupertino-om5.om.hp.com wrote:
> As far as the permeability is concerned, you can safely assume a value
> of 1.0 for the mu-sub-r. If you are using nickel, iron or cobalt as
> your conductor material or part of your alloy,then you need to worry
> about a non-unity value. The conductivity (real value) all it does is
> generate ohmic loss. The value you need to concern with is the
> frequency dependant skin effect wich essentially increases the ohmic
> resistance with frequency (R-sub-s).
> So, to answer you question, changing the material down the conductor
> path will essentially be insignificant except for ohmic losses. The
> impedance will stay the same (assuming the diameter is unchanged)
> Hans Mellberg
>
>
>______________________________ Reply Separator
_________________________________
>Subject: [SI-LIST] : Transmission Line Conductors
>Author: Non-HP-AHardie (AHardie@compuserve.com) at HP-ColSprings,mimegw5
>Date: 9/18/97 3:19 PM
>
>
>All the transmission line impedance formulae that I can find do not take
>into account the
>conductor's properties such as conductivity and frequency dependant
>permeability (mu).
>Does anyone know how a change in transmission line material part of the way
>along it's length
>affects the transmission line's performance?
>
>Alastair Hardie.
>
>
>