基于正交定向耦合器组合的微波功率测量方法

Microwave Power Measurement Method Based on Quadrature Directional Couplers

定向耦合器广泛应用于微波系统的功率测量.但定向耦合器的方向隔离度有限,两个方向的耦合输出信号存在一定程度地串扰,影响功率测量的准确性.为了解决这一问题,本文提出一种正交耦合测量方法.该方法采用一对相位差为90°的定向耦合器同时测量功率,通过对测量结果的计算处理,可消除方向串扰的影响.推导了正反向传输功率与正交耦合器组合功率测量值的关系,分析了正交偏差所产生的误差.为了确定耦合器的正交状态,提出了一种准确测量两个定向耦合器之间相位差的方法.实测表明正交耦合方法可有效提高功率和驻波比测量的准确性.

Directional coupler is commonly used in the microwave system to measure the forward and backward power.Due to the limited directional isolation of the coupler,the crosstalk existing between the bi-directional coupling output signals will influence the accuracy of power measurement.The quadrature directional coupling method is developed to solve this problem.A pair of directional couplers with a phase difference of 90°are used to measure the coupling output power simultaneously,and the influence of crosstalk can be eliminated effectively by processing the measurement data.The relationship between forward and backward power and the outputs of quadrature couplers is derived,and the error due to the quadrature deviation is analyzed.In order to determine the quadrature situation,the method to measure the phase difference between two couplers is roposed.The experiment shows that the quadrature directional method can improve the accuracy of power and VSWR measurement effectively.