3 port stripline circulator designing

I want to design 3 port stripline circulator .i know the frequeny, insetion loss,vswr.
i want to know the designing steps. &
my Questions
1.How internally the signal is going from one port to next port only , not to other port.
2.We are having different types of ferrite materials,how we have to choose the ferrite material for our required operation.
3.Which type of magnet we have to choose.