Re: [SI-LIST] : Transmission Lines Formulae

Kyung Suk (dan_oh@avanticorp.com)
Wed, 13 Jan 1999 11:29:07 -0800

ajmani@us.ibm.com wrote:
>
> The formulae provided in different reference books are not very accurate,
> but are subject to several approximations. It is good to use these
> formulae only for obtaining a ball park figure. For greater accuracy, one
> should use a 2-D, or 3-D field solver. Again, the PCB building processes
> have common tolerances of no better than +/- 10%, unless one is willing to
> pay big bucks for tighter tolerances.
>
> The best approach I have found out is to have the PCBs built based on your
> calculations/field solver analysis, and then perform an actual impedance
> measurement with TDR. The difference between calculated and actual
> impedance value is the adjustment you need to make for the PCB
> manufacturing process. Hence, it pays to stick with one fab for all your
> PCB needs.
>
> HyperLynx provides a reasonably accurate 2-D field solver as part of their
> Crosstalk analysis tool, and it is very easy to use.
>
> Regards, Ravinder
> PCB Development and Design Department
> IBM Corporation - Storage Systems Division

Upcoming Star-Hspice (1998.4) will include a BEM 2-D field solver also.

Regards,

___________________________________________________________________
Kyung Suk (Dan) Oh, Ph.D. (B) (510) 413-8197
Avant! TCAD (F) (510) 413-7743
46871 Bayside Parkway (e) dan_oh@avanticorp.com
Fremont, CA 94538 ksoh@iname.com

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