Analysis of magnetically coupled resonators [CST microwave studio]

Hi,
I have to optimize with CST studio suite a system of magnetically coupled resonators for wireless power transfer, so that the efficiency is maximum (therefore wireless power transfer between transmitter and receiver antenna is maximum).
Each antenna is made of a number of circular loop (concentric), with a certain step. I have realized the antenna configuration, initially placing them 25cm apart from each other. Now I should insert the source (a voltage source with an impedance of 50 ohm in series) and the adaptation circuit to be connected to the transmitting antenna, and a 50 ohm load to be connected to the receiving antenna. What instructions should I use under the heading 'set excitation'?

Once this is done, changing size, step and distance, I can achieve the maximum efficiency.
Thanks for your help.