coplanar stripline advantage

hi
could you please tell me what is the advantage of using coplanar strip line
instead of two isolated strip line ?
thanks

What is two isolated strip line?

http://www.sonnetsoftware.com/suppor...e_July2012.pdf

I found the article above interesting.

In my experience I have found that cpw and conductor backed cpw useful when the need arises to provide a convenient ground location for components that may be attached to the transmission line.

Modeling and fabrication of cpw and gcpw lines can certainly be a challenge. I have also been a part of hand waving discussions over the shielding of one relative to the other.