Circulator with 2 transformers

Have tried couple of days to design a circulator with 2 transformer sections in each branch, but never successful. 2 transformers could provide 3 reflection poles, thus could much improve the bandwidth.

I even tried hfss optimization, but at the end, it only gave me the response similar to one transformer circulator (2 reflection poles)

Has any friend here ever successfully designed one? No matter waveguide or coaxial.

Hope you can share your experience.

Thanks in advance.