Determination of the symmetric coupled line parameters in an inhomogeneous medium using reflected and transmitted waveforms

A measurement method for determining the symmetric coupled line parameters (the even and odd mode characteristic impedances and their phase velocities) in an inhomogeneous medium is described theoretically. The first and second terms of the power expansions of the reflection and transmission coefficients at the near end of the coupled lines are utilized for that purpose. The input function is a ramp waveform whose risetime is 0.2 ns. It is shown that very-short-duration pulses of positive or negative polarity can be created by the unequal phase velocities of the even and odd modes