Dear Hend,

you can follow your purpose in this link:

http://www.emtalk.com/mpacalc.php

In CST Microwave studio V. 2016, click on Home, click on Macro, new window will be open

Then select calculate, then go to analytical line impedance , new window will be open.

select suitable line feeding such as Coax, stripline, coplanar waveguide with ground etc.,

select suitable frequency, dielectric constant , thickness of substrate etc.,

target the impedance you want , write the targeted impedance in the box,

write different value of W ( width of the line) and click on calculate, vary value of W such that , desire value of impedance you get.

You can use the free package QUCS (http://qucs.sourceforge.net/), it has an analytical characteristic impedance calculator for several different types of transmission lines, and you can simulate the s parameters of your feed network.

You can use CST or HFSS it will be easy for that

or Advanced System Design ADS it's so easy