Dear All,
Aubrey Sparkman is exactly right. I use Ansofts tool and have just finished
an exhaustive
series of analyses on a felx cable for a tape head. BTW, we wanted to get
the L, C & tpd
values as well!! These values were obtained using the spice equivalent.


Thank you
Charles Grasso
Advisory Engineer
StorageTek
2270Sth 88th Street
Louisville CO 80027 M/S 4247.
Tel:303-673-2908
Fax:303-661-7115
email:[log in to unmask]
Web Site:  http://www.ewh.ieee.org/r5/denver/rockymountainemc/
<http://www.ewh.ieee.org/r5/denver/rockymountainemc/>




-----Original Message-----
From: Aubrey Keith Sparkman [mailto:[log in to unmask]]
Sent: Friday, July 02, 1999 9:58 AM
To: [log in to unmask]; CAI ZhongPing
Cc: [log in to unmask]; [log in to unmask];
[log in to unmask]; [log in to unmask];
[log in to unmask]; [log in to unmask]
Subject: Re: [SI-LIST] : Parallel tracks on Flexible PCB without Ground
Plane


CAI,
I have solved a similar problem using the technique suggested by  Steve
<addbook:add?vcard=begin%3Avcard%0Afn%3ASteve%20Weir%0Aemail%3Binternet%3Awe
irsp%40a.crl.com%0Aend%3Avcard%0A> Weir <[log in to unmask]>  in his message
dated Thu, 01 Jul 1999 04:33:39. The way to do this in Ansoft's tool would
be to re-label YOUR GND leads as GMETAL and solve for ALL your leads as
signals very far from the solver's ground plane.  The tool allows you to
"Zero" or "ground out" certain leads after it has completed the field
solution.  Grounding out the GMETAL leads will then cause the proper
transformation of the mutual coupling values to the values you need.

Aubrey Sparkman
SparkRight Solutions




CAI ZhongPing wrote:


Dear experts,

Sorry to disturb you again. :)  The following figure explains the case more
clearly:


   ________    ________    ________    ________
  |________|  |________|  |________|  |________|
     GND        Signal       GND        Signal


So they are not driven differentially. General tools calculate differential
impedance, right? Can just setting the distance to the plane very high get
correct result?


Thanks for your help and look forward to your reply.


Cai


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