基于非对称耦合线的小型宽带阻抗匹配器设计与实现

Design and implementation of miniaturized broadband impedance matcher based on asymmetric coupled line

阻抗匹配是微波电路设计中的重要环节。阻抗匹配器通常为窄带匹配且电路尺寸较大。非对称耦合线设计参数较多,相比于对称耦合线在设计上具有更大的自由度,因而可以达到更好的性能。基于非对称耦合线开发电路元件成为近几年研究的热点。所提出的基于非对称耦合线的阻抗匹配器设计方案,通过在耦合线之间引入反馈环节实现宽带匹配,并采用集总元件对传输线进行等效,缩小了电路尺寸、增大了匹配带宽,同时也提高了匹配器的可调节性。最后,对实际电路进行加工与测试,测试结果表明所设计的阻抗匹配器相对带宽可达50%以上,尺寸仅为7 mm×10 mm,可用于改善射频链路中元件之间的级间匹配。该匹配器在通带内可改善回波损耗6 dB,插入损耗为0.2~0.5 dB。

Impedance matching plays an important role in microwave circuit design.The impedance matcher is usually narrow-band with a large size.Compared with symmetric coupled line,asymmetric coupled line has higher degree of freedom in design,so it can achieve better performance and becomes the hot topic in recent years.In this paer,a design scheme of impedance matcher based on asymmetric coupled line was proposed.A feedback link was introduced to realize broadband matching,while lumped elements were used to replace the transmission lines.The circuit size was reduced,matching bandwidth was increased and the adjustability of the matcher was improved.Finally,the actual circuit was fabricated and measured.The result indicates that the fractional bandwidth is above 50%,and the size is only 7 mm×10 mm.The return loss can be improved by about 6 dB,while the insertion loss is 0.2-0.5 dB in the passband.