Abstract
Differential signaling is an important technique for voltage high-speed digital system
to avoid electromagnetic interference. Differential networks are characterized using
mixed-mode S-parameters that are typically obtained by conversion from single-ended
S-parameters or direct measurements. We found that the conversion matrix may affect
the conversion accuracy due to ill-conditioning. We study the condition number of the
conversion matrix using two test cases: broadside coupled striplines and edge coupled
microstrips.
We also develop a way to simulate differential S-parameters with true excitations
and apply it to characterizing the Power Distribution Networks which should not be
characterized by single-ended S-parameters due to ground bounce and IR drop.
Finally, recently developed causal Fourier continuation is employed to verify the
causality of single-ended and mixed-mode S-parameters. In addition, we use a causality
argument and the Fourier continuation based method to extract time delay from single-ended
S-parameters and then from mixed-mode S-parameters in the future.