Methods for the measurement of the frequency dependent complex propagation matrix, impedance matrix and admittance matrix of coupled transmission lines

摘要

A method for completely characterizing coupled transmission lines by short-pulse propagation is described. The complex frequency- dependent propagation matrix, impedance matrix and admittance matrix for a set of n parallel transmission lines can be determined by comparing the properties of two sets of coupled transmission lines of different length. Each transmission line set has two conductors of unequal length and ground conductors to form a coupled transmission line system. Each transmission line set can have uncoupled ends. An input pulse is provided at at least one node of each transmission line set. The complex frequency dependent propagation matrix of each transmission line set is determined by a comparison of the output pulses at the remaining nodes of each transmission line set which involves ratioing to cancel out the effect of the pad-to-probe discontinuity and the uncoupled ends which make it unnecessary to do any embedding. For a transmission line wherein the dielectric loss is negligible, the complex frequency dependent characteristic admittance can be determined from the propagation matrix and the empirically determined capacitance matrix. For a transmission line wherein the resistive loss is negligible, the frequency dependent characteristic impedance matrix can be determined from the propagation matrix and the empirically determined inductance matrix. Specific structures are used with the measurement method to determine these coupled transmission line parameters. The method is particularly useful to determine these parameters for transmission lines in semiconductor chip packaging substrates.