RE: [SI-LIST] : Cross hatched planes

Syed Huq (shuq@cisco.com)
Wed, 23 Jun 1999 22:19:35 -0700 (PDT)

John,

You may not be able to define a circular shape but a diamond shape is possible.
I will try to send you an example. XFX models the hatched ground quite
accurately.

Regards,
Syed.

>
> Syed,
>
> I use XFX to model the cross hatch also. However I realize that the meshed
> ground defined in the XFX is only good for rectangle.
> It is quite limited. I asked viewlogic's FAE about diamind or circular
> shapes but got not answer.
>
> How do you deal with this problem with XFX ? Is XFX accurate enough for
> hatch ground?
>
> Best Regards,
>
> John Lin
> CAE Engineer
> Quanta Computer Inc.
>
>
>
> -----Original Message-----
> From: Syed Huq [mailto:shuq@cisco.com]
> Sent: Saturday, June 19, 1999 5:09 AM
> To: si-list@silab.eng.sun.com
> Cc: shuq@cisco.com
> Subject: Re: [SI-LIST] : Cross hatched planes
>
>
> Hello,
>
> If you are using XFX(2-D from Quad), you can model the cross hatch using
> MESHED_GROUND. For example:
>
> MESHED_GROUND HORIZ_PLANE y: 27.80 29.20 P_X: 15.0 A_X: 10.0 P_Z: 15.0 A_Z:
> 10.0
> MESHED_GROUND HORIZ_PLANE y: 0.000 1.400 P_X: 15.0 A_X: 10.0 P_Z: 15.0 A_Z:
> 10.0
>
> Impedance becomes a function of your cross hatch geometry plus more..
>
> We have done this sort of study.
> Regards,
> Syed.
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> Syed B. Huq shuq@cisco.com ~
> Signal Integrity Engineer(ELB) ~
> Cisco Systems, Inc. ~
> Ph:(408)525-3399 Fax:(408)526-5504 ~
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
> >
> > I have a question regarding high frequency (over 500MHz) signals running
> > over ground planes that are cross hatched, which is commonly done on flex
> > circuits. The issue is how to accurately model the characteristic and
> > differential impedance for the flex circuit traces. If, for example, I
> use
> > a 2D field solver (where I assume an ideal ground plane) and am designing
> > for 100 ohms differential impedance, what percent increase in impedance
> > should I expect if the ground plane will actually be cross hatched?
>
>
>
>
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