Veri cation of Calculated Electrical Parameters ofTransmission Line Structures on Printed Circuit

A veriication of calculated electrical parameters of transmission lines on printed circuit boards is presented. Furthermore, the innuence of common manufacturing processes on the principle cross section of transmission lines and the resulting electrical parameters is subject of the investigations. With regard to existing manufacturing tolerances a sensitivity analysis is carried out taking account the most critical geometrical parameters. Transmission line parameters obtained by TDR-measurements and by numerical calculations are compared in order to verify the results of a BEM-algorithm with respect to accuracy and to validate the introduction of simpliications in describing the cross section of the transmission lines. Transmission lines on inner and outer layers of mul-tilayer printed circuit boards are treated separately due to diierent geometrical parameters. The results can be used for being able to deene ranges for geometrical tolerances of the PCB layer speciication which have to be met in order to guarantee prescribed electrical properties of the entire PCB. 1 INTRODUCTION The successful design of high speed printed circuit boards requires the knowledge of the dynam-ical behaviour of the interconnecting transmission line structures which is | assuming quasi-TEM wave propagation | described by the well known transmission line theory. This means, if losses can be neglected , the transmission lines can be characterised by their characteristic impedance Z L and their characteristic propagation delay T D or phase velocity v ph (T D = v ?1