A generalized broadband coupled-line based rat-race coupler with arbitrary power division ratios and free terminated impedances is proposed in this paper. Besides, rigorous closed-form equations with respect to electrical parameters are derived in the section of analysis. Furthermore, one shorted coupled-line section and two identical open-circuited stubs are employed to achieve the requirement of wideband and miniaturization. Owing to additional design freedom, the calculation of parameters becomes much more flexible. For demonstration, a prototype for 6-dB wideband rat-race coupler centered at 1 GHz with the fractional bandwidth of 51.69% and free terminated impedances is designed, fabricated, and measured. Good agreement between the simulated and measured results can be observed, which can verify the validity of the proposed design principle.

本文提出了一种具有任意功率分配比和自由端接阻抗的基于宽带宽带耦合线的大鼠种族耦合器。此外，在分析部分还导出了关于电参数的严格的闭式方程。此外，采用一个短路的耦合线段和两个相同的开路短截线来实现宽带和小型化的要求。由于额外的设计自由度，参数的计算变得更加灵活。为了演示，设计，制造和测量了以1 GHz为中心，分数带宽为51.69％和自由端接阻抗的6 dB宽带大鼠竞赛耦合器的原型。可以观察到仿真结果与测量结果之间的良好一致性，这可以验证所提出的设计原理的有效性。