X波段过模弯曲圆波导TM_(01)-HE_(11)模式变换器研究

Investigation of an X-band over-moded bent circular waveguide TM_(01)-HE_(11) mode converter

在波束波导和反射面天线的馈源应用中,为了产生低副瓣且方向图等化的高斯波束,需要将高功率微波转换为准高斯模HE11模辐射.本文利用弯曲圆波导可同时从TM01模产生TE11模和TM11模的原理,提出了采用双弯曲过模圆波导结构直接将TM01转换为HE11的模式变换器,避免了常规微波领域中首先将TM01转换为TE11再用波纹式或半径渐变式TE11-HE11转换器转换为准高斯波束功率容量不足或尺寸过长的不足.基于模式耦合理论和Taguchi优化算法对模式变换器的弯曲半径、相移直端长度及引入位置进行了优化,使输出的TE11和TM11成一定比率,以组成HE11模式,并对设计的模式变换器进行了全电磁波仿真分析,结果表明输出波束的标量高斯含量在9.05—9.8GHz范围内均高于99%,理论功率容量可达4.5GW.

In the application of low loss beam waveguides and high performance reflector antennas, high power microwave should be converted to quasi-Gaussian HE11 mode, to decrease side lobe level and increase feed coefficient. Based on the fact that TM01 mode converts to TE11 and TM11 mode at the same time in bent overmode circular waveguide, a TM01 to HE11 mode converter was proposed in this paper, which can convert TM01 mode to HE11 mode directly using a bent circular waveguide, the converter has higher power compacity than corrugated TE11-HE11 mode converter and more compact than TE11-TM01 mode converter added with smooth wall TE11-HE11 mode converter. The geometric parameters of the convertor were analyzed and optimized by using coupled mode theory and Taguchi method, to output the target modes content, 80% TE11 and 20% TM11 modes, which are primarily composed of HE11 mode. The optimized converter was analyzed using full electro-magnetic simulation method, the scalar Gauss ratio of the output beam is higher than 99% from 9.05 GHz to 9.8 GHz, the power capacity is as high as 4.5 GW.