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L波段宽带极化器设计与仿真
刘晓红
Subtype硕士
Thesis Advisor陈卯蒸
2012-05
Degree Grantor中国科学院研究生院
Place of Conferral北京
Degree Discipline天文技术与方法
Keyword射电天文 宽带 四脊 极化器 Hfss Cst
Abstract射电望远镜是射电天文观测的主要工具,灵敏度作为一项重要指标,与接收信号的带宽是成正比的。随着宽带数字终端的发展,接收机的带宽已经成为提高望远镜灵敏度的瓶颈。为提高射电望远镜的灵敏度,新疆即将建设的110米大口径望远镜计划采用宽带接收机,实现各个厘米波段的宽频带覆盖。厘米波段接收机主要包括馈源、极化器、低噪放、混频单元,其中,极化器的带宽是增加接收机带宽的关键制约因素。为了解决110米宽带接收机研发中的技术难点,针对L波段提出了本课题。
 通过深入调研国内外相关资料和文献,确定采用四脊OMT的形式。整个极化器由圆方波导转换,方波导到脊波导的过渡段,以及同轴脊波导转换三部分构成。其中,第三部分还包含同轴末端的匹配部分。圆方波导转换采用圆角方形波导的形式,方波导到脊波导过渡的主要部分是四个立体脊,起阻抗渐变的作用。同轴末端的匹配部分由短路匹配和吸波材料构成,其中短路匹配有短路块匹配和短路销钉匹配两种方法。
 在理解设计原理和微波相关知识的基础上,采用HFSS和CST两种三维电磁场仿真软件分别进行仿真,以验证设计的可靠性。首先在HFSS中建立了与两种短路匹配方法相对应的两个初始极化器模型,实现了模型的参数化,并求解了四个初始性能指标,分别是回波损耗、插入损耗、端口隔离度和交叉极化隔离。然后,结合现有的机械加工精度,在HFSS中对两个模型的关键参数进行了长时间的优化分析,得到了最优的模型。最后,将HFSS中优化好的模型导入到CST中,设置好正确的边界条件和激励,求解出了最优模型在CST中的仿真结果。
 结果证明,两个模型均能获得很好的性能,且尺寸较短小,而且HFSS仿真结果差别不大。另外,由于脊曲线是由若干采样点构成的折线,便于加工。但CST的仿真验证结果与HFSS的仿真结果还有一定的差距,有待进一步解决。
Other AbstractAs the main facility of radio astronomical observation, radio telescope’s typical target is its sensitivity. The sensitivity of radio telescope is directly proportional to the bandwidth of the received signal. With the development of wideband digital backend, the bandwidth of the radio receiver becomes a bottleneck of enhancing the sensitivity. Therefore, the radio receiver of the large 110m telescope to be built in XinJiang will use wideband technology to realize wideband coverage of cm bands. The cm band receiver mainly includes the feed, the polarizer, the low-noise amplifier and the mixing unit, of which the polarizer is a key restriction of the bandwidth of the receiver. In order to solve the technical problems in developing wideband receivers used in 110m radio telescope, we propose this topic in view of L band.
 After investigating considerably domestic and foreign relevant data and papers, I determined to use the quad-ridged OMT type. The entire structure includes three parts, which are the transition from circular waveguide to square waveguide, the transition from square waveguide to the quad-ridged waveguide, and the transition from quad-ridged waveguide to coaxial outputs. The third part also includes the terminal match part following the coaxial lines. The first part is a filleted square waveguide, and the main components of the second part are the four ridges, playing a role in gradual impedance change. The terminal match part includes two parts, which are the short match and the absorbing material. The short match has two ways, the shorting blocks way and shorting pins way, respectively.
 Based on understanding the principle of the design and related microwave knowledge, I used two kinds of three-dimensioned electromagnetic field simulated softwares to carry out my work, thus to confirm the reliability of the design. Firstly, I established two initial HFSS models according to the two different short match ways, parameterized the two models, and solved the four initial performance criteria, which are return loss, insertion loss, port isolation, and cross polarization. Secondly, considering the current machining precision, I carried out a long time optimization analysis on the key parameters of the two initial models using HFSS, and obtained two optimized models. Lastly, I imported the two optimized models to CST, established correct boundary conditions and excitation, and got the CST simulation results.
It proved that the simulation result of each short match way could obtain a very good performance with compact size and have a good coincidence in HFSS. Besides, as the ridge curve is a polygonal line consisting of several sampling points, it is ease of manufacture. However, the HFSS simulation results and the CST simulation results still have some difference, which has not been fully resolved.
Subject Area天文仪器、天文技术与数据
Pages83
Funding Project微波接收机技术实验室
Language中文
Document Type学位论文
Identifierhttp://ir.xao.ac.cn/handle/45760611-7/341
Collection研究生
射电天文研究室
Recommended Citation
GB/T 7714
刘晓红. L波段宽带极化器设计与仿真[D]. 北京. 中国科学院研究生院,2012.
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