Hi, Venkat: Besides CPW, microstrip and stripline, I believe coupled strips are also used. Basically, for those TLN spanning from 0 to high frequency, you need at least 2 conductors in order to have at least one propagating mode without cutting off frequency. However, you also don't want to use more than 2 because more than 2 conductors will create more than 1 propagating mode. When more than 1 propagating mode happens, it will cause dispersion and it will affect transmission quality no matter time or frequency domain signals are concerned. CPW contains 3 conductors and it has more than 1 propagating mode and it is not good in this aspect. Designers have to connect the two grounds together here or there in order to suppress the 2nd propagating mode. Certainly, CPW has other advantage such as low dispersion on Ereff, easy manufacturing because of no need for vias and easy to connect lumped elements to them because we can connect them on the surface and we do not need to dig holes.
All those parameers (s-parameters, TLN parameters, RLC equivalent circuits) are related anyway. IE3D is excellent for planar cricutis and you can use it for all these kinds of interconnects. Regards.