This study presents a compact transmission line topology to reduce the circuit size of single- and two-section branch line couplers (BLCs). The proposed transmission line is composed of a high impedance series line and one coupled line section. The coupled line section consists of two high impedance series lines and one coupled line. The proposed line is analysed with even-odd mode analysis to derive closed-form design equations. To validate the equations, a compact single- and two-section BLCs are designed at 0.85 GHz based on the proposed line. The physical size occupied by the proposed single- and two-section BLCs is 23 and 19.5%, respectively, compared to conventional BLCs. Moreover, the proposed transmission line demonstrates the harmonic suppression characteristic due to the coupled line section. As a result of which, the second- and third-order harmonic of the proposed BLCs are suppressed. The proposed BLCs are designed, fabricated, and tested.

中文翻译：

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基于耦合线段的紧凑型传输线拓扑结构使分支线耦合器小型化

这项研究提出了一种紧凑的传输线拓扑结构，以减小单截面和两截面分支线耦合器（BLC）的电路尺寸。提出的传输线由高阻抗串联线和一个耦合线段组成。耦合线部分由两条高阻抗串联线和一条耦合线组成。拟议的生产线将进行奇偶模式分析，以得出封闭式设计方程。为了验证方程式，基于拟议的线路，在0.85 GHz处设计了紧凑的单截面BLC和两截面BLC。与常规BLC相比，建议的单节BLC和两节BLC占用的物理大小分别为23％和19.5％。此外，所提出的传输线由于耦合线段而表现出谐波抑制特性。结果，所提出的BLC的二阶和三阶谐波被抑制。拟议的BLC进行了设计，制造和测试。