一、引言耦合线定向耦合器结构紧凑,制作简便,是雷达、通讯等整机设备中常用的微波元件。但是,它的主要缺点是对制造公差和奇、偶模相速的差异比较敏感,因此实际制造出来的定向耦合器方向性比较差,频带较窄。为了改善上述性能,常在简单的耦合线定向耦合器上做适当改进,如在耦合区加载,附加的介质使奇 I. INTRODUCTION Coupling line The directional coupler is compact and easy to manufacture. It is a commonly used microwave element in the complete equipment such as radar and communications. However, its main drawback is that it is more sensitive to manufacturing tolerances and to the difference between odd and even modes of phase velocity. Therefore, the directional coupler actually manufactured has a poor directivity and narrower frequency band. In order to improve the above performance, often simple coupling linear directional coupler to make appropriate improvements, such as loading in the coupling zone, the additional medium so odd