i have some matlab coddes of wilkinson power divider, stepped impedance lpf, lange coupler. imade these as part of my design lab in mtech in last semester. if u need them, i ca give to u. mail me at abhityagi85(at)gmail.com . for analysing, u have to be familiar with their operation, understand them, and then u can esaily model them accurately. though u will be simulating ideal characteristics as u ant take losses etc, but is a very good method to understand. u can refer to POZAR's book.