射电天文研究组知识库

为完成对太阳射电爆发15 MHz～15 GHz频谱的监测，云南天文台研发4套太阳射电频谱仪，频率覆盖范围依次为15～80 MHz, 100～750 MHz, 600～4 200 MHz和4～15 GHz,分别称为十米波、米波、分米波和厘米波太阳射电频谱仪。十米波段太阳射电频谱仪的谱分辨率和时间分辨率分别为7.6 kHz和1 ms;米波段和分米波段太阳射电频谱仪的谱分辨率和时间分辨率分别为9.5 kHz和10 ms;厘米波段太阳射电频谱仪的谱分辨率和时间分辨率分别为76 kHz和10 ms。每套设备包括天线系统、接收机和数字频谱仪。为实现超高谱分辨率，需要的快速傅里叶变换(Fast Fourier Transform, FFT)点数最高达到262 144,在现场可编程门阵列(Field Programmable Gate Array, FPGA)上，通过一个FFT IP核(Intellectual Property Core)不能实现如此高点数的快速傅里叶变换运算。对于大点数的快速傅里叶变换，需要对数据行列分解后做并行处理，从而将其转化为两个小点数的快速傅里叶变换。通过对并行算法的研究，使用Matlab对该算法进行仿真，并应用在数字频谱仪上。数字频谱仪测试结果与仿真结果具备良好的一致性，表明该算法在数字频谱仪上的成功应用。主要介绍太阳射电频谱仪的组成和基于现场可编程门阵列实现超高谱分辨率的方法。 

In order to complete the monitor of ultra-broadband spectrum for solar radio burst, Yunnan Observatories have designed and developed 4 solar radio spectrometers with the frequency range of 15 - 80 MHz, 100-750 MHz, 600-4 200 MHz and 4-15 GHz, which are called decametric, metric, decimetric and resolution centimetric solar radio spectrometer, respectively. For the decametric solar radio spectrometer, the spectral resolution and temporal resolution have reached 7. 6 kHz and 1 ms, respectively. For metric and decimetric, the spectral resolution and temporal resolution have reached 9. 5 kHz and 10 ms, respectively. For the centimetric spectrometer, the spectral and temporal resolution have reached 76 kHz and 10 ms, respectively. Each spectrometer includes antenna system, receiver and digital spectrometer. In order to obtain a spectrum with ultra-high spectral resolution, the maximum word length of FFT is 262 144, which cannot be achieved by one-time FFT in FPGA, the parallel FFT algorithm is need. For the large word length of FFT, the data need to be transformed into a FFT with two small word length by doing a row decomposition and then parallel processing. In this paper, the algorithm is studied and simulated by using Matlab, then is applied to digital spectrometer. The test results of the digital spectrometer are good consistency with the simulation, indicating the successful application of the algorithm on the digital spectrometer. This paper introduces the composition of solar radio spectrometer and the method of implementing ultra-high resolution based on FPGA.