how can I get the S parameter with using incident wave ??

hi
Could you tell me how can I get the S parameter with excitation of incident wave ??
I try to simulate the transmission and reflection of split-ring resonators (SRRs) , I used the wave port in the past , now , I want to use the incident wave for excitation , but I can not get the S parameter with using incident wave .

Could you tell me how to get it , and in what condtions I can not get it ??

thank for your kindness!!