CPW

Hi, I tried to calculate the CPW parametrs using the formulation given in RAINEE SIMONS: coplanar waveguide circuits, components and systems, wiley interscience. this is the only place which deals with synthesis of CPW. but has errors, i checked with the orignal ref and made corrections. well getting to point, there two sets of formulae are given 1st calclates slot width given all other things, and second central conductor width. But both these sets are not consistent with each other, like i tried to simulate both equations in MATLAB, and answers in both were not consistent with each other. For eg i calc, S= 272Micrometer for er=13, Z=50, w=100u, h=100u, now for second set, its giving w = 18u, for the same data as abive (s= 272u)!!!! can anyone help me out