|Place of Conferral||北京|
|Keyword||射电天文 宽带 四脊 极化器 Hfss Cst|
|Other Abstract||As 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.
|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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