The convergent properties of the multimode method are discussed . finally a diplexer employing h - plane t - junction and preassigned e - plane metal - insert branching filters is given . and the scattering parameters of the un - optimized diplexer were obtained by the computer program 在论文的最后部分设计了两个e面金属插片滤波器,并把它们作为通道滤波器和h面t形结组成双工器,用矩形波导双工器的分析程序对它进行了分析,给出了分析结果。