Development Of 10-50 MHz Low Frequency Radio Astronomical Digital Receiver And PC Software

It is known that low frequency(<50 MHz)radio signals have attracted wide attention of researchers over the past two decades.Low frequency radio observation can usually be used to used to study the solar radio burst process,diagnose plasma information,study the intermittent radiation mechanism of Jupiter-dominated planets,and to explore other major issues such as supernova remnants.Radio observations are usually carried out with ground-based instruments,however,only several observing system has been established in the beginning of 21th century.Therefore,in this paper we developed a digital receiver and PC software for ground-based low-frequency radio astronomy observation with recent electronic information technology,which has been successfully applied it to the Qitai Observatory(QTO)radio observation system in the low frequency band(10-50 MHz)of Xinjiang Qitai.In this thesis,we first give a brief introduction of the Qitai observatory and the developed system(including the logarithmic periodic antenna,analog front end,digital receiver and PC software etc.).Detail descriptions of the observing system are then presented for the digital receiver and host computer software from the aspects of key device selection,simulation and design,test and verification.The digital receiver is composed of acquisition card and industrial computer.The design includes three parts:(1)The analog-to-digital converter(ADC)was selected with AD9265 chip with a sampling rate of 125.The spectrum distribution of the sampled signal is simulated by MATLAB.(2)The field programmable gate array(FPGA)designed with XC7K410T,and essential processing,i.e.adding window function,Fourier transform,power spectrum and accumulation,data frame structure,data truncation etc.Are carried out in it.(3)Receiver time synchronization design,adding NTP time synchronization server to ensure the accuracy and consistency of system time.In order to meet the requirements of radio observation display and storage,a targeted PC software solution is developed.The software development is based on Microsoft Foundation Classes(MFC)and TeeChart control.The software supports real-time spectrum display,data storage and interactive operation,and has the functions of full-band intensity map display and image automatic preservation.In order to ensure the correctness of software design,the functions of each part of the software are tested,and the important strategies and key indicators of the software are introduced.Finally,the relevant contents are tested,including the time domain or frequency domain signal test of the receiver,the joint test of the QTO system,and the solar radio storm events observed by the QTO system are taken as examples.By comparing the observation results with Australian equipment,it is concluded that the detection accuracy of the system is more precise and the detection frequency band is lower.After testing,the performance of the independently developed digital receiver and PC software are as follows:detection frequency of 1-62.5 MHz,frequency resolution of 15.3 kHz,time resolution of 0.5-32 ms,and dynamic range of 72 dB.The equipment was put into operation in June 2021 at Xinjiang Qitai Observation Station(QTO),and solar radio eruptions were captured for several times.In the future,it is expected to carry out the research on planet radio based on Jupiter.At the same time,it can be combined with Chang’e-4,Ming’antu imager and Chashan solar radio observation station of Shandong University to carry out satellite-ground cooperative observation,and promote the research of low frequency radio in China.