Design procedure for waveguide duplexer

How about your procedure and your experiences?
I firstly design two filters,with the formula in the textbook.and then
use HFSS to optimize them.but found it is too time-consuming,and the
result is poor.
I planned to have two good filters,and connect them with a T junction,
and choose the proper space between the T junction and the two filters,
but,the filter optimization is not well done,and full optimization for the duplexer
is difficult to implement.

Hope for your tips and advices!

A "duplexer" is a high powered limiter, often PIN diode or gas discharge tube based.

A "diplexer" is a filter system with a common port and two different-frequency ports.

You must research what a "singly terminated filter" means in order to properly design a diplexer filter.