Abstract: In rectangular waveguide discontinuity analysis by mode matching, the traditional method infers a different expression according to a different discontinuity. The program creates a serious inconvenience, so there need be a unified approach to analyzing the rectangular step. This paper infers the unified generalized s-parameter matrix formula of the step in the thick diaphragm and in the E-plane septum by mode matching. Finally, two rectangular band pass filter examples are included. The curve results agree well and the calculation time is greatly shortened compared with the HFSS, which verifies the validity of this technique.

Key words: mode matching, generalized s-parameter matrix, diaphragm, E-plane septum