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

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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