Hi, We have a traces which we want to have an impedance of 75Ohm. Under the trace there will be a ground plane. So fare calculating trace width would be easy. But we need ground on both sides of the trace also. Does anyone know a formula for trace width embed in ground on three sides? Any help would be appreciated. -- mfg Oliver Gundolf ------------------------------------------------------------ | Lucent Technologies | | Abt. LB33 (PCB-Engineering)| Thurn-und-Taxis-Strasse 10 | | D-90411 Nuernberg | Deutschland / Germany | | Name: Oliver Gundolf | Fax: +49-911-526-4822 | | Telephon: +49-911-526-3916 | E-Mail: [log in to unmask] | | Responsibilitys: Layout access and switching PCB | ------------------------------------------------------------