Experimental Characterisations of Coupled Transmission Lines

Coupled transmission lines are experimentally characterised by using 4-port s-parameter measurements in the broad frequency band (up to more than the 20 GHz). The test patterns are designed and fabricated by using a BGA package process. Symmetrical coupled transmission lines are decoupled into two eigen modes that can be readily determined from the measured s-parameters. Then signal transient and crosstalk noise are directly determined from the measured s-parameters. It is shown that not only are the transmission line parameters frequency-variant, but also the frequency-variant effects and non-ideal characteristics of transmission lines have substantial effect on the signal transients and crosstalk noises.