[SI-LIST] Re: N-port problem in interconnects

  • From: Amitava Bhaduri <bhadhua@xxxxxxxxxxxx>
  • To: Geoff Stokes <gstokes@xxxxxxxxx>
  • Date: Fri, 31 Oct 2003 12:47:47 -0500 (EST)

Dear Geoff,

My 2-conductor system is placed on a lossy substrate ground plane. But I
don't know the typical value of the conductivity of such a substrate. I am
following the TSMC0.18 micron technology. Any idea what the substrate is
made of and what the typical conductivity of it is?? I couldn't find the
details in TSMC0.18 micron technology brochure.

Regarding the coupling capacitance and the capacitance to ground I am
intending to use FASTCAP.

Thanx,
Amitava

On Fri, 31 Oct 2003, Geoff Stokes wrote:

> Dear Amitava and Patrick
>
> I would be interested in further discussion of this problem.  I have a
> couple of questions.
>
> In your 4-terminal metal system, what considerations do you have about the
> underlying substrate?  At high frequencies, should you consider some kind of
> ground plane, or at least, coupling to other conductors?
>
> Did you obtain your z-parameters from an EM simulator?
>
> Cheers
> Geoff
>
> > -----Original Message-----
> > From: Patrick Zilaro [mailto:pzilaro@xxxxxxxxxxxx]
> > Sent: 30 October 2003 22:26
> > To: bhadhua@xxxxxxxxxxxx; si-list@xxxxxxxxxxxxx
> > Subject: [SI-LIST] Re: N-port problem in interconnects
> >
> >
> > I think you got it.  Cadence Spectre represents each port
> > with a positive
> > and a negative terminal.  This is just like, if you were
> > measuring these
> > s-parameters using a VNA and microprobes.  The microprobes each have a
> > positive and a negative terminal.  By the way, some circuit
> > simulators that
> > can handle s-parameters choose to combine all the negative
> > terminals into
> > one common "reference" terminal.  Spectre keeps them separate.
> >
> > Regards,
> >
> > Patrick Zilaro
> > SI Packaging Engineer
> > Broadcom Corporation
> >
> > -----Original Message-----
> > From: si-list-bounce@xxxxxxxxxxxxx
> > [mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of Amitava Bhaduri
> > Sent: Thursday, October 30, 2003 2:03 PM
> > To: si-list@xxxxxxxxxxxxx
> > Subject: [SI-LIST] N-port problem in interconnects
> >
> >
> >
> >
> > Hi,
> >
> > I am trying to model the interconnects using the "nport" feature of
> > spectre. Take for example I have 2 conductors (A1-B1 and
> > A2-B2). A1, B1,
> > A2, B2 are connected to other circuit elements, like transistors for
> > example. I am trying to model only the interconnect portion.
> >      _                           _
> >     B1  | |                 B2  | |
> >     | |                         | |
> >     | |                         | |_____________
> >     | |_____________            |_____________  |
> >     |____________  |                          | |
> >                  | |                          | |
> >                  | |                          | |
> >                  | |                          | |
> >                  | |                          |_|
> >               A1 |_|                        A2
> >
> > I am able to obtain a (2 x 2) impedance matrix [Z] for this
> > 2-conductor
> > system. Using the formula (Z-1)(Z+1)^-1, the impedance
> > parameters can be
> > converted to s-parameters (as "nport" of spectre operates on
> > s-parameters).
> > The problem is how do I represent this 2-conductor system
> > in spectre "nport" format. If you do "spectre -help nport"
> > you will see
> > that the instance statement looks like:
> >
> > Name ( t1 b1 [t2] [b2] ... ) nport <parameter=value> ...,
> >
> > where the terminals should be given in pairs. Can this
> > 2-conductor system
> > be realized as 2-port network? What would the common terminals be (-ve
> > terminal) in this case? In this 2-port interconnect network can I
> > represent the first port as (A1, B1) where A1 is +ve terminal
> > and B1 is
> > -ve terminal, while the second port being (A2, B2) where A2 is +ve
> > terminal and B2 is -ve terminal?
> >
> > (note: this is only an instance of a 2-conductor system. The
> > same problem
> > can be extended for any "n-conductor system", where n=1,2,3,4,5...etc)
> >
> > Would appreciate any help on this.
> > Thanks,
> > Amit
> >
> >
> > Amitava Bhaduri
> > Research Assistant
> > 527 ERC
> > University of Cincinnati
> > OH - 45220
> > ph : 513-556-3025
> >
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Amitava Bhaduri
Research Assistant
527 ERC
University of Cincinnati
OH - 45220
ph : 513-556-3025

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