Power Combiners, Impedance Transformers and Directional Couplers
Power Combiners, Impedance Transformers and Directional Couplers
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功率合成器、阻抗变压器和定向耦合器
DOI：
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发表时间：
2007
期刊：
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通讯作者：
A. Grebennikov
中科院分区：
文献类型：
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作者：
A. Grebennikov
分支线耦合器或混合器在六十多年前首次被描述;然而，它们的精确合成问题多年来一直是一个谜[53]。最初，基于在偶模和奇模中获得的结果的叠加，将分支线混合电路作为四臂对称网络进行分析[54]。通过将偶模矩阵和奇模矩阵写在一起，可以得到分支线的特性阻抗和耦合到不同端口的特性阻抗。十年后，一种通用的合成方法可以应用于多分支杂交体的任何结构，该方法基于理查德变量S = jtanθ对除了180°相变之外的S → 1/S变换的不变性[55]。因此，利用可用于分支线混合电路的高精度计算机设计技术，可以产生有用的0至15 dB耦合范围内的任何耦合值。已用于相控阵雷达大型复杂馈源的波导设计结构紧凑，幅度和相位特性高度可预测，并且可以处理非常高的功率。分支线混合器的同轴、微带或带状线实现提供了具有中等带宽能力的简单平面结构，高达约2/3倍频程。对于具有标准50Ω源阻抗和负载阻抗的完全匹配情况，当其横向分支的特性阻抗为50 Ω且其纵向主线的特性阻抗为时，图30所示的微带分支线混合器表示3 dB定向耦合器，其中臂1中的功率在臂2和3之间均匀分配，相移为90°。没有功率被输送到臂4，因为流过不同路径（λ/4和3λ/4的长度）的信号在该端口处具有相同的幅度和相反的相位。当所有反射功率都耗散在50 Ω镇流电阻中时，对于来自输出的相等反射系数，分支线混合电路不依赖于负载失配水平。然而，在实践中，由于四分之一波长传输线的要求，这种单级正交分支线混合的带宽被限制在10- 20%。图31显示了计算得出的中心带宽频率处匹配的单段分支线混合电路的频率带宽特性，负载阻抗为ZL = Z 0 = 50 Ω，其中C12为插入损耗，计算结果为输入端功率比50 2 35 4 /。= Ω这篇关于耦合器和合路器结构的多部分文章继续研究使用各种拓扑结构的微波混合电路
Microwave hybrids The branch-line couplers or hybrids were firstly described more than six decades ago; however, the problem of their exact synthesis remained a puzzle for a number of years [53]. Initially, the branch-line hybrid was analyzed as a four-arm symmetrical network based on a superposition of the results obtained in the even and odd modes [54]. By writing the even and odd mode matrices together, the characteristic impedances of the branch lines and coupling into different ports can be obtained. A general synthesis procedure which can be applied to any structure of a multibranch hybrid, based on an invariance of the Richard’s variable S = jtanθ to the transformation of S → 1/S apart from a 180° phase change, had become available a decade later [55]. As a result, with highly precise computer-design techniques available for branchline hybrids, it became possible to generate any coupling value in the useful 0 to 15 dB coupling range. Waveguide designs which have been used in large complex feeds for phase-array radars, are compact, highly predictable in amplitude and phase characteristics, and handle very high power. Coaxial, microstrip or stripline implementations of branch-line hybrids provide simple planar structures of moderate bandwidth capability, up to about 2/3 of an octave. For a fully matched case with standard 50Ω source and load impedances, when the characteristic impedances of its transverse branches are 50 Ω and the characteristic impedances of its longitudinal main lines are the microstrip branch-line hybrid shown in Fig. 30 represents a 3-dB directional coupler, for which power in arm 1 divides evenly between arms 2 and 3 with the phase shift of 90°. No power is delivered to arm 4, because the signal flowing through different paths (lengths of λ/4 and 3λ/4) have the same amplitude and opposite phases at this port. The branch-line hybrid does not depend on the load mismatch level for equal reflected coefficients from the outputs when all reflected power is dissipated in the 50-Ω ballast resistor. However, in practice, due to the quarterwavelength transmission-line requirement, the bandwidth of such a single-stage quadrature branch-line hybrid is limited to 10-20%. Figure 31 shows the calculated frequency bandwidth characteristics of a single-section branch-line hybrid matched at the center bandwidth frequency with the load impedance ZL = Z0 = 50 Ω, where C12 is the insertion loss calculated as the ratio of powers at the input 50 2 35 4 / . = Ω This multi-part article on coupler and combiner structures continues with an examination of microwave hybrids using various topologies