Development Of Multi-Channel Digital Receiver For Solar Radio Observation In The Meteric-Wavelengh Regime In Chashan Solar Observatory

Solar eruptions such as flares and coronal mass ejections are the origin of catastrophe events in the solar-terrestrial space,which affect human activities both in the space and on the ground.And it is of importance to develop observation and monitor of solar eruptions.Radio observation is one of the two observing window of the Sun,in which abundant features appear in the meteric-wavelengh regime.Therefore,study on observations in this waveband has become important approach to reveal the physical process of solar eruptions.With the development of digital technology and radio communication,great progress has been made in developing solar radio detection technology,and thereby the instruments.As the routine module in the solar radio observation system,a digital receiver or receiving system has become the essential R&D part of the entire system.Compared with traditional receivers,digital receivers could usually yield high resolution,high sensitivity,good stability,and flexible design.We note that the performance of digital receivers can be evaluated significantly with the application of high-speed and high-precision Analog to Digital Converters(ADCs)and very large-scale Field Programmable Gate Arrays(FPGAs).However,the current observing system at home and aboard could barely observe fine structures with high time and together with spectral resolution during solar bursts.According to the above considerations,we plan to improve the receiving system working in the frequency range of 25～110 MHz of the low-frequency array solar radio observation system in Chashan Solar Observatory(CSO)in Shandong University,The main research contents are as follows:(1)Modularization has been carried out in the design of the receiver,and based on which the overall architecture of the receiver is designed.According to different functionality,the receiver contains data acquisition module,real-time data processing module,data transmission module,driver module and host computer software module,in which ADC and FPGA are the core devices of performance improvement.Therefore,we select the FPGA chip XCKU115 with massive computing resources to be the controlling and processing core device.In addition,an 8-channel ADC acquisition card is designed with a sampling rate of 250 MSPS and a resolution of 16 bit,which can yield high performance in the frequency range of 25～110 MHz of the low-frequency array solar radio observation.(2)Function configuration and data decoding have been realized in multi channels of the ADC.In details,the data acquisition has been realized by the configuration of clock and register in the acquisition card;the Double Data Rate Low Voltage Differential Signaling(DDR LVDS)data from ADC card to FPGA board has been decoded by the serial-to-parallel conversion and optimization timing.According to these efforts,the performance of the digital receiver are as follows:the Spurious Free Dynamic Range(SFDR)of～70 dBc,the Signal-to-Noise Ratio(SNR)of～60 dB,which ensure the high-quality observation of the Sun.(3)The Peripheral Component Interconnect Express(PCIe)are designed to be the communication protocol.The performance of different modes of PCIe has been tested,and we finally adopt the method of XDMA with interrupts to design the algorithm of PCIe,which satisfies the requirements of uploading the data of solar radio spectrum with a transmitting speed of-5.5 GB/s.(4)The software in the host computer has been developed to receive the solar radio spectrum from the FPGA board.The software can not only store the data,but also display the spectrum chart and dynamic spectrum line chart in real time.In addition,there are some other functions designed in the software,such as downloading parameters,unattended observation and so on.The soft is designed with graphical interface,which provides good experience for researchers.In the end,the multi-channel digital receiver has been working in the frequency range of 25～110 MHz of the low-frequency array solar radio observation system in CSO,which has processed routinal observations for more than half a year.There is an adjustable temporal resolution of 0.2～8.4 ms and a frequency resolution of 30 kHz in the system,which can provide scientific data for the theoretical study of the physical process of solar eruptions.