Looking for info about vivaldi antenna design

Hi to all,
I am going to do project. It is designing of vivaldi antenna for 2 - 6 GHz frequency range on FR4 (Er = 4.4) substrate with CST MS. Could anyone tell me about the informations or websites or books.
Thank you for advices.

About Substate you can refer https://www.edaboard.com/viewtopic.p...hlight=vivaldi :D

also one CST paper http://www.cst.com/Content/Applicati...cle.aspx?id=15

To start with :D :D
Regards
GV