I so far faced with farfields,today i want to discuss about it and i learn more about it, in CST Microwace and Lumerical you can see this polar contour.So i searched some to find a defintion about farfields.
The far field of the feed antenna can be used as a source in the reflector dish simulation. Both models can be simulated with appropriate solvers.
Fig1: Using farfeilds plot in antenna optimization
So old puzzle in practical microwave problem is coupling.every more confined power and field in direction antenna can increase more efficeiency and less loss. you can download this pdf for more info.