about radiation pattern,vswr,return loss

hii,
1.my doubt is why we want to measure the radiation pattern while simulating the antenna in hfss,and what is the purpose of measuring vswr in antenna design ,is there is any coorelation between the vswr and return loss.
2.correlate the vswr,radiation pattern definition in detail with hfss software
3.for what via is used in antenna
4.how we can optimize the ebg structure design to rise the gain