应用案例：利用短截线降低短接式贴片天线交叉极化的仿真

[{"insert":"——转自公众号《老猫电磁馆》 作者 孙刚"},{"attributes":{"align":"right"},"insert":"\n"},{"attributes":{"bold":true},"insert":"摘要"},{"insert":"\n\t文献（Neng-Wu Liu, “Cross-Polarization Reduction of a Shorted Patch Antenna With Broadside Radiation Using a Pair of Open-Ended Stubs,” IEEE Trans. Antennas Propag., vol. 68, no. 1, pp. 13-20 Jan. 2020.）指出传统的短接式贴片天线在TM"},{"attributes":{"script":"sub"},"insert":"1/2,2"},{"insert":"模式下，其表面的电场分布大致如下图所示："},{"attributes":{"align":"justify"},"insert":"\n"},{"insert":" "},{"insert":{"image":"https://files.eteforum.com/article/202209/3fe3170a55eb919e.png"}},{"attributes":{"align":"center"},"insert":"\n"},{"insert":"\t考虑其在H平面（YOZ平面）上的远场辐射特性，|E"},{"attributes":{"script":"sub"},"insert":"phi"},{"insert":"|分量由E"},{"attributes":{"script":"sub"},"insert":"2"},{"insert":",E"},{"attributes":{"script":"sub"},"insert":"3"},{"insert":"确定，|E"},{"attributes":{"script":"sub"},"insert":"theta"},{"insert":"|分量由E"},{"attributes":{"script":"sub"},"insert":"1"},{"insert":"确定，在特定的尺寸下会出现|E"},{"attributes":{"script":"sub"},"insert":"theta"},{"insert":"|过大而|E"},{"attributes":{"script":"sub"},"insert":"phi"},{"insert":"|过小的情况，即交叉极化的现象。"},{"attributes":{"align":"justify"},"insert":"\n"},{"insert":"\t为了降低上述的交叉极化现象，可以在贴片天线上增加一对如下图所示的短截线，改变贴片天线的电流分布，用以削弱远场的|E"},{"attributes":{"script":"sub"},"insert":"theta"},{"insert":"|分量并增强电场的|E"},{"attributes":{"script":"sub"},"insert":"phi"},{"insert":"|分量。"},{"attributes":{"align":"justify"},"insert":"\n"},{"insert":" "},{"insert":{"image":"https://files.eteforum.com/article/202209/237373fbb3dfcc58.png"}},{"attributes":{"align":"center"},"insert":"\n"},{"insert":"\t为了降低贴片天线的有效的辐射面积，可以将上述短截线进行了折弯处理。此时，改进后贴片天线TM"},{"attributes":{"script":"sub"},"insert":"1/2,2"},{"insert":"模式的工作频点已经与原贴片天线TM"},{"attributes":{"script":"sub"},"insert":"1/2,0"},{"insert":"模式的工作频点较为接近，对比两者的交叉极化现象，改进后的天线仍然具有明显的优势。"},{"attributes":{"align":"justify"},"insert":"\n"},{"insert":" "},{"insert":{"image":"https://files.eteforum.com/article/202209/f765b1b6e5da2ed3.png"}},{"attributes":{"align":"center"},"insert":"\n"},{"insert":"\t本文基于ANSYS HFSS软件仿真分析了一种上述的短接式贴片天线，计算天线的工作频点、贴片表面电流分布，远场辐射方向图，验证了文献中的结论。"},{"attributes":{"align":"justify"},"insert":"\n"},{"insert":"\t "},{"attributes":{"align":"justify"},"insert":"\n"},{"attributes":{"bold":true},"insert":"HFSS仿真流程和结果"},{"insert":"\n2.1短接式贴片天线"},{"attributes":{"align":"justify","header":3},"insert":"\n"},{"insert":"\t本文仿真的短接式贴片天线如上图所示，其中基片材质为F4B，不考虑Patch和Ground的厚度，设为PEC边界，基片和Ground的面积为150mm x 150 mm，基片厚度3mm，Patch面积为40mm x 26 mm，馈电点距离Patch的边界（x方向）为20.5 mm，Patch一端通过短接引脚接地。根据天线尺寸，预算TM"},{"attributes":{"script":"sub"},"insert":"1/2,2"},{"insert":"模式的工作波长约为40mm，即工作频点大约在7.5GHz左右，扫频计算得到其工作频点为7.75GHz。"},{"attributes":{"align":"justify"},"insert":"\n"},{"insert":" "},{"insert":{"image":"https://files.eteforum.com/article/202209/7f1c6522659e6b1b.png"}},{"attributes":{"align":"center"},"insert":"\n"},{"insert":"\t在工作频点下仿真计算贴片天线的表面电流分布和YOZ平面的远场方向图（GainPhi和GainTheta）。电流分布表面贴片天线的工作模式为TM"},{"attributes":{"script":"sub"},"insert":"1/2,2"},{"insert":"模式，远场方向图表面此时天线存在严重的交叉极化现象，尤其是theta=0方向附近。"},{"attributes":{"align":"justify"},"insert":"\n"},{"insert":" "},{"insert":{"image":"https://files.eteforum.com/article/202209/05bc217326eb96d9.png"}},{"attributes":{"align":"center"},"insert":"\n"},{"insert":{"image":"https://files.eteforum.com/article/202209/2e04605f3428eba1.png"}},{"attributes":{"align":"center"},"insert":"\n"},{"insert":"2.2含有短截线的贴片天线"},{"attributes":{"align":"justify","header":3},"insert":"\n"},{"insert":"\t为了降低上述的交叉极化现象，可以在贴片天线上增加一对如下图所示的短截线，短截线的宽度为0.3mm，这里对短截线的长度进行参数扫描，取值为17.4mm、22.4mm、27.4mm和32.4mm。S"},{"attributes":{"script":"sub"},"insert":"11"},{"insert":"的计算结果表面，随着短截线长度的增加，工作频点逐步降低。"},{"attributes":{"align":"justify"},"insert":"\n"},{"insert":" "},{"insert":{"image":"https://files.eteforum.com/article/202209/f6ecd055e5266619.png"}},{"attributes":{"align":"center"},"insert":"\n"},{"insert":"\t远场方向图表明，随着短截线长度的增加，交叉极化的现象逐步改善。"},{"attributes":{"align":"justify"},"insert":"\n"},{"insert":{"image":"https://files.eteforum.com/article/202209/deb51a35dbcb247a.png"}},{"insert":"  "},{"insert":{"image":"https://files.eteforum.com/article/202209/f3a710502ae3c865.png"}},{"attributes":{"align":"center"},"insert":"\n"},{"insert":{"image":"https://files.eteforum.com/article/202209/13bc2c28004100f1.png"}},{"insert":{"image":"https://files.eteforum.com/article/202209/ab6b61689a066426.png"}},{"attributes":{"align":"center"},"insert":"\n"},{"insert":"2.3含有短截线的贴片天线"},{"attributes":{"align":"justify","header":3},"insert":"\n"},{"insert":"\t为了降低贴片天线的有效的辐射面积，可以将上述短截线进行折弯处理，本文中折弯处理的短截线总长度为22.4mm。其工作频点在2.67GHz。"},{"attributes":{"align":"justify"},"insert":"\n"},{"insert":" "},{"insert":{"image":"https://files.eteforum.com/article/202209/51666ca26e39bbb2.png"}},{"attributes":{"align":"center"},"insert":"\n"},{"insert":{"image":"https://files.eteforum.com/article/202209/955a64bd169121aa.png"}},{"attributes":{"align":"center"},"insert":"\n"},{"insert":{"image":"https://files.eteforum.com/article/202209/f9ae2d1bac462692.png"}},{"attributes":{"align":"center"},"insert":"\n"},{"insert":"改进后贴片天线TM"},{"attributes":{"script":"sub"},"insert":"1/2,2"},{"insert":"模式的工作频点（2.67GHz）已经与原贴片天线TM"},{"attributes":{"script":"sub"},"insert":"1/2,0"},{"insert":"模式的工作频点（1.91GHz）较为接近，对比两者的交叉极化现象，改进后的天线仍然具有明显的优势。\n"},{"insert":{"image":"https://files.eteforum.com/article/202209/c2e82a76670d84d0.png"}},{"insert":{"image":"https://files.eteforum.com/article/202209/5f0314eab800ed7d.png"}},{"attributes":{"align":"center"},"insert":"\n\n"},{"attributes":{"bold":true},"insert":"结论"},{"insert":"\n传统的短接式贴片天线在TM"},{"attributes":{"script":"sub"},"insert":"1/2,2"},{"insert":"模式下，H平面存在严重的交叉极化现象；\n通过增加一对短截线，可以通过改变贴片天线表面的电流分布，从而改善交叉极化；"},{"attributes":{"align":"justify"},"insert":"\n"},{"insert":"通过，仿真计算可以验证上述结论。"},{"attributes":{"align":"justify"},"insert":"\n"},{"insert":"\n"}]