Transmission line modelling

hi,
I want to model a transmission line (2 line) can anyone help me with some docs,
Any tools available etc.

Thanks,
pavan

Microstrips / cables / something else?

Actually my spec say it can be any of them.
S parameters are given (4-port, mixed mode)
but only magnitude is given not phase,
if phase is also given it would have been easy.
Can you help me with it.
I am using spectre.