Hey Andy, I just visited your web site and downloaded the Polar
Instruments, LTD Controlled Impedance Calculator. It calculates
Microstrip, Embedded Microstrip, Stripline, Offset Stripline and Coated
Microstrip. Just select the graphical Icon for each calculation and plug
in the known values. It's the best one I have ever seen! Thanks to all
who made it possible and keep up the good work!!!!

Chris Taylor
Senior Printed Circuit Designer
LXE, Inc.
125 Technology Parkway
Norcross, GA 30092
voice: (770) 447-4224 X3242
fax: (770) 447-6928
e-mail: [log in to unmask]


>----------
>From:  Andy Burkhardt[SMTP:[log in to unmask]]
>Sent:  Tuesday, August 19, 1997 6:21 AM
>To:    [log in to unmask]
>Subject:       Re: [DESIGNERCOUNCIL] DES: Distributed Capacitance Calculations
>
>At 10:10 15/08/97 -0400, you wrote:
>>Does anyone have a formula for calculating the distributed
>>capacitance of copper planes? I Know I have seen this before
>>in PCD magazine but I seem to have *lost* the issue.
>>
>>Thanks in advance for your assistance.
>>
>>Jeffrey McGlaughlin
>>BFGoodrich Avionics Systems Inc.
>>1105 Schrock Road
>>Suite 800
>>Columbus Ohio 43229
>>(614)825-2232 (voice)
>>(614)825-2037 (fax)
>>[log in to unmask]
>>
>
>Jeff,
>
>Not sure if this is what you're after:
>
>Capacitance of a parallel plate capacitor (or parallel copper planes)
>is given as:
>
>      C = Eo x Er x A
>          -----------
>               D
>
>Where:
>       C  = capacitance in Farads      (F)
>       Eo = permittivity of free space (8.854 x 10exp-12) (F/m)
>       Er = relative permittivity  (typically FR-4 is 4.6 at 1 MHz) (no
>units)
>       A  = area of the plates (or planes) (m x m)
>       D  = distance between plates (or planes) (m)
>
>This equation neglects fringing effects.
>
>Best regards
>
>Andy Burkhardt <[log in to unmask]>
>Tel: + 44 1481 53081
>Fax: + 44 1481 52476
>http://www.polar.co.uk
>----------------------------------------------------------------------
>World leaders in PCB faultfinding and controlled impedance measurement
>----------------------------------------------------------------------
>