a coaxial to microstrip transitiion

Hi

I have successfully simulated with FEKO a microstrip patch antenna with coaxial probe excitation(via hole). My question however, is irelevant to the program used.

I now want to approximate a microstrip line excitation but i am buffled as to how i will model the excitation. Do i just enter a voltage source at the edge of the microstrip line or should i create a more complicated model that includes the coaxial to microstrip transition?
Any ideas by users of any simulation program will be of great help.