[SI-LIST] FW: Wire impedance at HF

Hi Rob;

The model consists of a 150X150X125 mil high box with a 10 mil dia X 125 mil
long copper rod running down the middle of it.
There are 2 50 ohm ports on either end. Reference plane is at the port. I
think you answered by question , impedance is relative and it is conceivable
in light of the impedance formula that the reactance can go negative , you
will have to excuse my memory lapse . To answer your questions in the second
email - no other metal except the default boundaries - port assignment is
wave - the entire top and bottom of the box are ports .

Thanks

Justin Tabatchnick
Intel
-----Original Message-----
From: Rob Hinz [mailto:rob@xxxxxxxxxx]
Sent: Monday, May 20, 2002 5:20 PM
To: justin.tabatchnick@xxxxxxxxx; si-list@xxxxxxxxxxxxx
Subject: RE: [SI-LIST] Wire impedance at HF


Hi Justin,

Sure it's possible, depending on how you configured your simulation. In
general, your wire will form a transmission line. It will be referenced
either to itself, if you use it to terminate an existing transmission line,
or to some other reference conductor if not. In either case, unless the
transmission line defined by your wire or terminated by your wire, is
terminated in a perfectly matched impedance, the impedance seen looking into
the system will alternate between inductive and capacitive behavior as
frequency increases.

Zin = Z0*(Zload + j*Zo*tan(beta*length))/(Zo + j*Zload*tan(beta*length))

Beta = 2*pi/wavelength

I may have totally missed the mark here because I don't understand how you
set up the problem in HFSS. Please elaborate on that a little and perhaps I
can give you a better answer!

Regards,

Rob Hinz
Principal Engineer
SiQual Corporation
rob@xxxxxxxxxx
503-885-1231 (voice)
503-885-0550 (fax)
www.siqual.com


 -----Original Message-----
From:   si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of Tabatchnick, Justin
Sent:   Monday, May 20, 2002 4:44 PM
To:     si-list@xxxxxxxxxxxxx
Subject:        [SI-LIST] Wire impedance at HF


HI All;

I recently simulated in HFSS a straight wire imbedded in a dielectric . As
predicted it behaved as an inductor between .6 GHz and 6 GHz , however above
6 GHz the reactance was capacitive which does not make sense . Is this at
all possible or is there something wrong with my model.

Thanks

Justin Tabatchnick
Intel, Sacramento
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