射电天文研究组知识库

射电天文在HF-VHF频段采用天线组阵的方式进行观测，根据平方公里阵列（Square Kilometre Array, SKA）的要求，每个阵列单元天线的增益、结构一致性、稳定性、阻抗变化趋势和极化纯度等方面需要达到较高指标，才能满足太阳、木星、再电离纪元等多种测量在极化测量、天线跟踪稳定性以及接收机宽带匹配等方面的需求。根据SKA requirement 2165:极化纯度2135-38和每极化方向灵敏度2814-15提出的性能需求，以及在总结原有设计的经验后，针对10～90 MHz频段，设计了一种适用于HF-VHF的新型倒“V”型栅板偶极子天线，具有重量轻、风阻小等优点，在10～90 MHz的超宽频段内阻抗变化缓慢、极化纯度良好。其中，在阻抗变化方面，天线的阻抗实部从0.8Ω到631.132Ω变化，优于低频射电阵列（Low Frequency Array, LOFAR）的天线，降低了接收机匹配难度和噪声；在极化纯度方面，天线整体轴比小于0.41 dB,对于太阳射电爆发等强极化信号具有良好的极化隔离度。 

Radio astronomy uses antenna array for observation in the HF⁃VHF frequency band. According to the requirements of SKA (square kilometer array), the gain, structure consistency, stability, impedance change trend, polarization purity and other aspects of each array element antenna need to reach high indicators to meet the requirements of Sun, Jupiter, Epoch of reionization and other measurements in polarization measurement, antenna tracking stability and receiver broadband matching and other aspects. According to the performance requirements proposed in SKA requirement 2165： polarization purity 2135-38 and sensitivity per polarization 2814-15, and after summarizing the experience of the original design, a new type of inverted “V” grid dipole antenna suitable for HF⁃VHF for the 10-90 MHz frequency band is designed in this study, which has the advantages of light weight and small wind resistance. The structure has the advantages of slow impedance change and good polarization purity in the ultra⁃wide frequency band of 10-90 MHz. Among them, in terms of impedance change： the real part of the impedance of the antenna changes from about 0. 8 Ω to 631. 132 Ω, which is better than the low⁃frequency array antenna of the low⁃frequency radio array, reducing the difficulty of receiver matching and noise; in terms of polarization purity： the overall axial ratio of the antenna is less than 0. 41 dB, with good polarization isolation for strong polarization signals such as solar radio bursts.