Re: EGG for Transmision Line Package Models

I alluded to the problem of coupled lines when I said we may need an extension to spice to represent them. The only sure way to represent coupled lines in standard spice today is to break them into sections and represent these sections in terms of circuit capacitances and mutual inductances. This is very unpalatable. However if we are willing to add a coupled line extension to spice, we can represnt these lines is in terms of their short circuit per unit length rlgc matrices.These matrices provide the most compact representation of coupled lines and also many field solvers directly generate these matrices. Following is an example of the essense of this representation. The IBIS contribution will then be the extension to spice to represent coupled lines!!

NTL 1 2 0 3 4 0 L=0.002 rlgc_name=twolines
.data rlgc twolines
.r matrix
4.01 0
0 4.01
.l matrix
...
.g matrix
...
.c matrix
..
.end data rlgc twolines

Here the key word "NTL" identifies the description as a coupled line . The nodes 1 and 2 represent the input terminals, 3 and 4 rperesent the output and 0 is the refernce terminal. (In this case it is the ground). L=0.002 represent the length. The example here assumes fixed unit (meter for example). The rlgc data immediately follows the transmission line description.

>
> Hello Kumar:
>
> Thanks for your comments. You are correct -- what we are trying
> to describe is a open ended circuit topology and by incorporating
> a full (perhaps SPICE?) netlist description of the interconnection into
> the .pkg file we would have a general solution. However, I am
> unsure on one point. How do you describe coupling between transmission
> lines using just a topological description of the circuit? Does the user have
> to build a circuit where L's and C's are added between all the coupled nodes (and
> does this really represent the coupling in the form the simulator tools need
> and use) or are the matrixes still required? If they are required, how do
> you indicate which circuit elements the matrix is trying to describe the coupling
> between? Just some food for thought.....
>
> Regards,
> Stephen
>
>
> >Kumar Writes:
> >
> >I have problem with this type of extension to IBIS format . Here we have open
> >ended circuit information and we are trying to reinvent a circuit format.
> >The best way to include open ended package information , in my view is in
> >the form of a spice sub circuit. Once you have defined the external terminals
> >and there is a mapping of these terminals to buffer output and device pins, the
> >spice circuit allows you to put any number of transmission line sections,
> >inductances , capacitances and or combination of lumped and transmission line
> >elements. An extension to coupled transmission line sis RLGC matrixes with non
> >zero length.
>
>
>
>
>
Received on Tue Apr 25 10:20:19 1995