Models for calculation of impedance, capacitance and signal speed for traces in a PCB follow below.

The calculation is made for Microstrip, Embeded Microstrip and Stripline.

At the end of this page there is also two models for calculating the differential impedance between two traces.

**General set-up for all models below: **

Relative permeability (er):

Micro Strip

*(The model is valid for
0.1<w/h<2.0 and 1<er<15)*

**w=****t=****h=**

**Z**0=

**C**0=

**t**pd=

Embedded Micro Strip

*(The
model is valid for 0.1<w/h<2.0 and 1<er<15)*

**w=****t=****h=****H**=

**Z**0=

**C**0=

**t**pd=

Strip Line

*(The
model is valid for w/(2h+t)<0.35 and t/(2h+t)<0.25)*

**w=****t=****h=****h1=**

**Z**0=

**C**0=

**t**pd=

Differential Micro Strip

**w=**
**t=**
**h=**
**s=**

**Z**0=

**Z**diff=

Differential Strip Line

**w=**
**t=**
**h=**
**s=**

**Z**0=

**Z**diff=

References:

- High-Speed Digital Design, Howard Johnson/Martin Graham ISBN 0-13-395724-1

- Information from http://www.UltraCAD.com

- RF Design Guide, Peter Wizmuller, ISBN 0-89006-754-6

Do You have questions concerning this site, be welcome to mail: skottanselektronik@skottanet.se

Last updated: 2008-06-17

© Sören Nilsson