CST 中waveguide port的設(shè)置問題

請問在CST中采用waveguide port源時(shí)，有如下提示：
waveguide port is too short, the waveguide must be homogenous for at least three mesh planes along propagation direction.
我能看懂上面的意思，但是我設(shè)置的波導(dǎo)口前的微帶線很長了啊，為什么還提示我這個(gè)有問題？究竟問題出在什么地方？
謝謝。

Try to enlarge the size of the waveguide port.

By simulating many times, I found the reason that the materials defined in the simulation are not homogenous along the waveguide port propagation direction, for instance, two materials are overlapping by mistake.

能不能用漢語簡單的說說整個(gè)仿真的步驟