浅析等效源反射系数以及K.Shimaoka测量方法的局限性

Analysis of the Equivalent Source Reflection Coefficient and Limitations of K. Shimaoka’s Measurement Method

等效源反射系数在微波功率测量与测量结果的不确定度评定中占有决定位置。首先介绍了在稳幅信号源系统中的源反射系数,和使用三端口器件测量功率比值时等效源反射系数之间的关系,从失配因子的角度解释了等效源反射系数中“等效”的含义。其次,简要介绍了日本K.Shimaoka提出的利用网络分析仪与三端口器件测量等效源反射系数方法的工作原理与使用的局限性。最后,以N型功分器和定向耦合器为测量对象,基于K.S方法与传统公式方法在1~18GHz频段进行了相关实验与结果的比较与验证。结果表明,K.Shimaoka的等效源反射系数测量方法具有一定局限性,由于该计算方法中获得的传输系数之差较小,该项容易对细微变化敏感,因此不适用于使用方向性较好的三端口器件(如:定向耦合器)时的等效源反射系数测量。

The equivalent source reflection coefficient plays a crucial role in microwave power measurement and uncertainty evaluation.This paper first discusses the relationship between the source reflection coefficient in amplitudestabilized signal source systems and the equivalent source reflection coefficient when measuring power ratios using threeport devices.The concept of"equivalent"in the equivalent source reflection coefficient is explained from the perspective of the mismatch factor.Next,the working principle and limitations of K.Shimaoka's method for measuring equivalent source reflection coefficient using a network analyzer and three-port devices are briefly introduced.Finally,experiments and comparisons are conducted using N-type power dividers and directional couplers as measurement objects,based on K.Shimaoka's method and the traditional formula method in the 1-18 GHz frequency range.Results indicate that K.Shimaoka's method for measuring equivalent source reflection coefficient has certain limitations.Due to the small difference in transmission coefficients obtained in this calculation method,it is sensitive to minor changes and thus unsuitable for measuring equivalent source reflection coefficients when using three-port devices with good directionality(such as directional couplers).