使用矢量网络分析仪测量多波束天线

[{"attributes":{"bold":true},"insert":"1. 引言"},{"attributes":{"align":"justify"},"insert":"\n"},{"insert":"在微波无源器件调试过程中，我们常常使用矢量网络分析仪（以下简称矢网）测试器件的S参数，最常分析的就是反射系数和传输系数幅度和相位。由于我们通常只会用到矢量网络分析仪的两个端口，所以对于多端口微波器件的测量就会用到宽带的匹配负载，也就是当器件中的两个端口与矢网的端口1和端口2连接之后，其余的所有的端口应当接上匹配负载，除非另做他用。"},{"attributes":{"align":"justify"},"insert":"\n"},{"attributes":{"bold":true},"insert":"2. 平面Rotman透镜的测量"},{"attributes":{"align":"justify"},"insert":"\n"},{"insert":" "},{"insert":{"image":"https://files.eteforum.com/article/2034/b69d3fedb1159417.png"}},{"attributes":{"align":"center"},"insert":"\n"},{"insert":" "},{"insert":{"image":"https://files.eteforum.com/article/2034/bce487a59f46e2f8.png"}},{"attributes":{"align":"center"},"insert":"\n"},{"attributes":{"background":"#d6d6d6"},"insert":"图1 平面Rotman透镜的测量"},{"attributes":{"align":"center"},"insert":"\n"},{"insert":"采用矢网对该透镜进行测量时，输入端口1~7依次与矢量网络分析仪的端口1相连接，输出端口8~17依次与矢网的端口2连接，且其余输出端口连接同轴匹配负载。经测量得到端口1~7输入时端口8~17的输出幅相数据，为了验证仿真设计方法的有效性，将实测结果与仿真结果对比如下："},{"attributes":{"align":"justify"},"insert":"\n"},{"insert":" "},{"insert":{"image":"https://files.eteforum.com/article/2034/098c23c6383acd29.png"}},{"attributes":{"align":"center"},"insert":"\n"},{"attributes":{"background":"#d6d6d6"},"insert":"图2 Rotman透镜反射系数"},{"attributes":{"align":"center"},"insert":"\n"},{"insert":{"image":"https://files.eteforum.com/article/2034/4ed3e076b206c5bd.png"}},{"attributes":{"align":"center"},"insert":"\n"},{"attributes":{"background":"#d6d6d6"},"insert":"图3 端口1馈电时输出幅相（10GHz）"},{"attributes":{"align":"center"},"insert":"\n"},{"insert":{"image":"https://files.eteforum.com/article/2034/48e0be6548de796d.png"}},{"attributes":{"align":"center"},"insert":"\n"},{"insert":" "},{"attributes":{"background":"#d6d6d6"},"insert":"图4 端口4馈电时输出幅相（10GHz）"},{"attributes":{"align":"center"},"insert":"\n"},{"attributes":{"bold":true},"insert":"结果分析："},{"attributes":{"align":"justify"},"insert":"\n"},{"insert":"1）从反射系数来看，仿真和测量结果有一定的差异，在9~11GHz的频带内，反射系数都低于-10dB，阻抗带宽较宽；"},{"attributes":{"align":"justify"},"insert":"\n"},{"insert":"2）从幅相数据来看，低副瓣Rotman透镜的实测的输出幅度明显低于仿真结果，当端口1输入时，实测与仿真的输出相位差别也比较大；"},{"attributes":{"align":"justify"},"insert":"\n"},{"insert":"3）实测幅相数据由于幅度不对称，幅度椎削达不到要求，副瓣性能恶化较为严重，且输出幅度较小，会降低天线阵列的增益。"},{"attributes":{"align":"justify"},"insert":"\n"},{"insert":"分析以上结果可知实物测量得到的性能较差，主要原因是由于Rotman透镜压合带来的加工误差，从定位孔来看，有一定偏移，这样会造成耦合缝有一定遮挡，影响耦合能量的大小，且会对相位造成影响。"},{"attributes":{"align":"justify"},"insert":"\n"},{"insert":"3. "},{"attributes":{"bold":true},"insert":" 多波束天线的测量"},{"attributes":{"align":"justify"},"insert":"\n"},{"attributes":{"bold":true},"insert":" "},{"insert":{"image":"https://files.eteforum.com/article/2034/af863bace8f8ad77.png"}},{"attributes":{"align":"center"},"insert":"\n"},{"attributes":{"background":"#d6d6d6"},"insert":"图5 10×10基片集成波导缝隙阵列天线"},{"attributes":{"align":"center"},"insert":"\n"},{"insert":{"image":"https://files.eteforum.com/article/2034/faf4082181b45b00.png"}},{"attributes":{"align":"center"},"insert":"\n"},{"attributes":{"background":"#d6d6d6"},"insert":"图6 多波束缝隙阵列天线系统"},{"attributes":{"align":"center"},"insert":"\n"},{"insert":"将上述系统置于微波暗室中进行远场测量，测量时矢网的端口1接上X波段的标准喇叭天线，端口2通过长线缆接上远端的多波束天线，通过单片机控制不同的输入端口形成指向不同的波束，测量结果如图7所示，从图中可以看出在9.8GHz、10GHz和10.2GHz时，输入端口1～7分别馈电形成的波束指向分别为-31°、-21°、-11°、0°、11°、21°、31°，副瓣电平都在-10dB以下，随频率变化波束指向几乎不发生的改变。边缘波束（端口1）相对于中间波束（端口4）增益下降小于3dB左右，在实际的测量中，由于缝隙阵列天线中波导之间存在互耦，当扫描角度增加时互耦增强，也会导致输入阻抗失配，从而使增益下降。"},{"attributes":{"align":"justify"},"insert":"\n"},{"insert":" "},{"insert":{"image":"https://files.eteforum.com/article/2034/1a2069cb2e85781f.png"}},{"attributes":{"align":"center"},"insert":"\n"},{"attributes":{"background":"#d6d6d6"},"insert":"图7 多波束缝隙阵列天线实测E面方向图"},{"attributes":{"align":"center"},"insert":"\n"},{"attributes":{"bold":true},"insert":"4."},{"insert":" "},{"attributes":{"bold":true},"insert":"总结"},{"attributes":{"align":"justify"},"insert":"\n"},{"insert":"上述的微波器件或者天线系统都可以通过是德科技的矢网完成测量，测量过程中需要注意的是：在测量前最好要按照工作频率对矢网进行校准，由于矢网刚启动时温度较低，最好等待一段时间待噪声稳定之后再进行测量。"},{"attributes":{"align":"justify"},"insert":"\n"},{"insert":"——转载于网络"},{"attributes":{"align":"right"},"insert":"\n"},{"insert":"\n"}]