高功率微波同轴阻抗变换器优化设计及功率计算

Optimal design and power capacity calculation for high power microwave coaxial impedance convertor

在高功率微波应用中,同轴线的阻抗匹配十分重要。通过同轴线内导体的渐变,可以实现阻抗变换与阻抗匹配。内导体渐变可以采用多项式、余弦、指数等函数形式。用时域有限差分方法计算同轴线的反射系数,以同轴线内导体渐变段的长度和反射系数达到最小为目标,采用遗传算法优化渐变段的结构参数,得到了反射系数为0. 015、渐变长度为148mm的同轴线阻抗变换结构。在一套具有16节点的Beowulf型并行计算机系统上采用主从式并行计算技术完成了计算,缩短了遗传算法搜索时间。最后计算和分析了该同轴线阻抗变换结构的带宽和微波功率容量,该结构峰值功率达8. 734MW。

The coaxial impedance convertor plays a very important role in the field of high power microwave. The impedance of a coaxial line can be converted by gradually changing the diameter of the inner conductor of the coaxial line, and some functions such as the polynomial, the cosine, the exponent and etc,can be applied to describe the curve of the diameter variation. In this paper, the finite-difference time-domain method (FDTD) was used to calculate the reflection coefficient in the coaxial line, and Genetic Algorithm (GA) was adopted to optimize the curve in order to design a convertor with a shortest length of the diameter-changing inner conductor and a minimal reflection coefficient. The optimization calculation of the GA was parallelized in the master-slave model and run in a Beowulf system with 16 nodes to improve its efficiency. As a result, a convertor was designed, whose reflection coefficient is 0.015 and the length of the conductor is 148 mm. The power capacity and bandwidth of the convertor were computed and analyzed. Results show its power capacity is as high as 8.734 MW.