Two improvements in the iteration method for mode converter design are presented, I. E. A reasonable initial step value in every iteration is given and coupled lines of less contribution are ignored to improve bandwidth. A TE01-TE11 mode converter is designed with the improved iteration method, whose ratio of waveguide radius to free space wavelength is 2. 765 5. Simulation results show that its relative bandwidth reaches 6%, total length is 600 mm, and conversion efficiency is 99. 14% at the central frequency. The total calculation time is 40 s. The CST simulation result agrees well with the coupled mode simulation one.%对模式变换器的迭代设计方法做了改进:给出了合理的迭代步长初始值取值方式；在迭代时只考虑了贡献较大的几条耦合线,而忽略了贡献小的耦合线,从而改善带宽.利用改进的迭代设计方法设计了波导直径与自由空间波长比值为2.7655的TE01-TE11模式变换器,总长度为600 mm,相对带宽为6％,中心频率转换效率为99.14％,总计算时间为40 s.利用CST软件进行了仿真验证,结果吻合较好.
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