lumped port calibration

HFSS newbie here

I am trying to simulate an Interconnect line test structure mouted on a Silicon substrate. Its basically 2 lines in Parallel and i need to define 2 ports on either side to get the S Parameters. Question is, If I use Lumped Gap source to define the Ports,

How do I Draw the Calibration and Impedance Lines? Can Someone describe how to do it or Does anyone have any Graphical Examples or links?

Thanks

Added after 52 minutes:

I have attached a Drawing of the Structure... it is Top view, and i have labled the Pads a,b,c and d for easy reference... where do the impedance and calibration lines go?

If you have HFSS_9 you can use a driven terminal solution method.
Go to the http://www.ansoft.com/products/hf/hfss/ and you'll find many examples in the folder Reviews and News.

Thanks, but i have looked at some of the articles but i couldnt find any description on how to define a port..

I'm using HFSS 8.5 and i believe there is a choice of eigenmode or driven solution.. i chose driven.

So far i have been getting an error message that the port is not defined correctly as the conductors are shorted.. the pictures show how i assigned the T, C and I lines (Terminal, Calibration and Impedance).. can someone comment on this assignment?

Hi,
for your model
I would draw a rectangle between the
terminal a and b and a rectangle between terminal c and d
Select these rectangle and assign lumped port to them.

Draw impedance and calibration lines from the middle of the edge
on terminal a to the middle of the edge on terminal b

Do the same for terminal c and d

You should think to lumped porte as a kind of voltage source
terminal line indicate the points where you attach the terminal of the voltage source

Rugbyfun

I wouldn't use lumped source for this configuration. lumped source should occupy tiny space (so that the fields between the two terminals are kind of uniform, so that a voltage can be defined...). The "gap" in your case is too wide. So change to wave port (there is a tutorial somewhere in this forum for coplanar waveguide). If gap source is absolutely required, you should make it a 4 port network, then figure out how to obtain the 2 port s-parameter from your 4 port result.

rugbyfun,

i think it works, thanks.. heres another question... if i have a piece of metal over an oxide layer and a substrate, and i want to find the s parameters of the metal (refer to the picture) How do i assign the ports if i use Lumped gap source, now that i dont have a ground? Wave ports wont work because wave ports are not supposed to touch "existing materails" (this structure is enclosed in an AirBox)

Hi,

I have difficulty in understanding the use of the lumped source.Could you guys explain when and how do I use the lumped source? Thanks.

I think lumped gap source ports are only useful when you need an excitation port inside a structure. If all the ports are defined on the border of the box, you only have to use wave ports.
For your problem, I think wave port with terminal activated is more appropriate. The terminal can be defined between the two lines. I always set calibration and impedance lines using the same coordinates than terminal arrow.
Are these two lines microstip ones with gnd plane under them ?

Added after 8 minutes:

>evoplus
To understand lumped gap source ports, try reading this file. It explains how to define ports in HFSS 8.5
(It comes from HFSS CDROM)