快速优化折叠波导器件中矩形过渡结构的理论方法（英）

本文推导了基于模式耦合理论的方程组，用于加快和简化折叠波导器件中矩形过渡结构的设计过程。作为功率耦合结构的一个重要组成部分，两种常用的结构将被考虑用来匹配折叠波导慢波结构的矩形波导TE10模式和标准输出矩形波导中的TE10模式。通过比较发现，在同样的反射水平下，锥形过渡结构比阶梯过渡结构长得多，但同时前者却自然具有更快的带宽和对结构误差不敏感的特性。作为算例，设计了220 GHz折叠波导返波管中可能用到的阶梯过渡结构和锥形过渡结构，并进行了误差分析。设计过程中用到的理论方法最终用数值模拟的方法进行了验证，取得了很好的一致性。基于该高精度理论方法的设计耗时不过几分钟。

Theoretical method for fast optimization of rectangular transition structure in folded waveguide devices

In this paper, the analytical equations based on mode-coupling theory are derived to facilitate the design process of rectangular transition structure in folded waveguide devices. As an important component of the power coupler, two common categories of structures are considered to match the TE10 modes in rectangular waveguide in folded waveguide slow wave structure into the TE10 mode in the standard rectangular waveguide port. By comparison, the tapered transition structure is much longer than the laddered transition structure with the same reflection requirement, whereas the former has a naturally much broader frequency bandwidth and less sensitivity to configuration errors. As an example, both the laddered and tapered rectangular transitions are designed and error-analyzed for 220 GHz FW Backward Wave Oscillator (BWO). The theoretical method adopted in design process is finally verified by numeric simulation, which shows excellent agreement. The design period based on the accurate theoretical method is only several minutes.