作为140GHz共焦波导回旋行波管放大器设计中的一个创新部分，关于准光学注入结构的设计方法将详细论述.归因于高斯光束对频率扰动的欠敏感特性，这样的注入结构具有比传统波导插入耦合器更大的带宽.注入系统包括耦合天线、镜面变换器和波纹波导三个部分，最终在高于50%功率注入水平下达到6.8GHz的带宽，并克服了可能的寄生模式振荡和由加工误差导致的注入效率迅速下降的问题.

As a part of the innovative design of the 140 GHz gyrotron amplifier loaded with confocal waveguide, the design process of the quasi-optical input launcher is comprehensively demonstrated. Owing to the relative insensitivity of the Guassian optics to the frequency fluctuation, the bandwidth of this type of power coupler could be drastically larger than the typical inserted waveguide coupler. The input launcher comprised of the antenna coupler, the mirror transformer and corrugated waveguide guarantees 6.8 GHz bandwidth with respect to >50% power injection efficiency, solving the problem of parasitic resonances and unexpected efficiency shrink simultaneously.