Manuscript received April 25,1987;
revised October 7;
1987. This work was supported in part by the European Community ESPRIT Research Program under Project 255. E. Pettenpaul;
H;
Kapusta;
A;
Weisgerber;
Mampe;
and J. Luginsland are with Siemens AG;
Components Group;
D-8000;
Munich;
West Germany. I. Wolff is with the Department of Electrical Engineering and Sondcr-forschungsbereich 254;
University of Duisburg;
D-4100;
Duisburg;
West Germany. IEEE Log Number 8718473;