小型化高方向性的微带双定向耦合器设计

为解决弱耦合时微带平行耦合线定向耦合器方向性低的问题,提出了适用于大功率场合的小型化高方向性微带双定向耦合器。基于传统四分之一波长平行耦合三线微带双定向耦合器结构,采用扇形微带电容加载可明显减小耦合器尺寸并增大隔离度,通过耦合边缘引入锯齿结构进一步提高了方向性。负载电阻采用扇形微带短截线接地设计,避免电气化过孔,使得加工更加简单。设计了一个中心频率为915 MHz、耦合度为20 dB的微带双定向耦合器,利用HFSS仿真软件对耦合器结构进行优化设计,并做了实物加工和测试。实测结果表明,在中心频率处耦合度为20.2 dB,方向性达到32.1 dB;在0.74~1.35 GHz频带内,输入匹配良好,耦合度波动小于0.5 dB,方向性高于20 dB。

Design of Microstrip Dual Directional Coupler with Miniaturization and High Directivity

In order to solve the problem of low directivity of parallel coupling line microstrip directional coupler in the case of weak coupling, a miniaturized high-directivity microstrip dual directional coupler suitable for high-power occasions is proposed. Based on the traditional quarter-wavelength parallel-coupled three-line microstrip dual directional coupler structure, the size of the coupler can be significantly reduced while the isolation of the coupler can be increased by using microstrip radial stub capacitance, and the directivity can be further improved by introducing sawtooth structure into the coupling edge. The load resistance grounding adopts microstrip radial stub design to avoid electrification via holes, which makes the processing simpler. A microstrip dual directional coupler with a central frequency of 915 MHz and a coupling degree of 20 dB is designed. HFSS simulation software is used to optimize the design, and the prototype is fabricated and measured. The measured results show that the coupling degree at the center frequency is 20.2 dB and the directivity reaches 32.1 dB. In the frequency band of 0.74 GHz to 1.35 GHz, good input matching is obtained while the fluctuation of coupling degree is less than 0.5 dB and the directivity is higher than 20 dB.