Define an arbitrary EM wave

Hello
I am new in Comsol and i have a problem :
i want to calculate SAR for SAM phantom for different types of EM waves. but the source of EM waves ( signal generator ) isn't important. is there any wave to just define wave equation ? for example just define an incoming Gaussian wave and see its effects ?
Can i use Comsol model (SAR in human head) and remove the antenna and define an incoming EM wave instead of it ?