how to design vivaldi antenna?

hello
i would like to design vivaldi antenna for my final year project.
my supervisor asked me to use CST MWS.
this is my first time using this software.
can anyone tell me as first step which one should i choose.
brick or rectangular shape?

thanks.

Check out the following links, these will get you started.

Design An X-Band Vivaldi Antenna
Vivaldi Antenna - Microwave Encyclopedia - Microwaves101.com

And I think you can find some design documents online.

is there any formula to determine the dimension of vivaldi antenna?

one more thing, how to define the ports of vivaldi antenna?

Ask your advisor whether you can use HFSS (much better tool IMO ;) ) but is also has the antenna design toolkit that will automatically create a vivaldi (continuous or stepped) antenna in HFSS including the ports, boundaries, and excitations. It will be a much faster start for your work.

I have never heard of the formula. Please let me know if there is.