Design Of Radio Signal Digital Receiving And Analyzing System

Solar activities such as sunspots,flares,and coronal mass ejections have serious impacts on wireless communications,satellite communications,power grids,and human health.Human beings have carried out ground and space detection of radio bursts in the solar system for decades,but the characteristics and mechanism of solar radio bursts and their changes have not yet been fully revealed.The establishment of a radio observation system is an important means of studying solar activities.The current solar radio observation system has the problems of low frequency resolution and time resolution and a single observation mode,making it difficult to observe the fine structure of solar radio bursts.According to the requirements of frequency resolution,time resolution and fine structure measurement of solar radio bursts in low-frequency solar radio observation,this paper combines dynamic spectrum observation technology with synthetic aperture technology,and develops a set of digital sensors that can be used for local single antenna at the same time.Digital receiving terminal for receiving and multi-site long-baseline interferometry observations.The core acquisition card of the digital receiving terminal system is composed of a high-performance ADC board and an FPGA board.This architecture can give full play to the advantages of the two units to improve real-time processing capabilities.(1)Aiming at the problem of insufficient frequency resolution and time resolution of the solar radio observation system,an under-sampling sub-band acquisition architecture is designed,which not only reduces the system sampling rate and the pressure of data calculation and transmission,but also improves the system resolution.(2)According to the demand for time and frequency synchronization in synthetic aperture technology,a time synchronization algorithm for digital receiving system is proposed,which realizes self-adaptive time reference selection and submillisecond precision time stamp.(3)In the process of solar radio observation,there is a problem that the frequency domain signal loses part of the information,and the time domain signal is difficult to achieve real-time observation.It is designed to support two modes of time domain acquisition and frequency domain acquisition at the same time,and supports timefrequency Seamless switching between domain modes.The test results show that the system has finally realized the ability to receive and analyze radio signals in the 15-350 MHz frequency band,with a maximum frequency resolution of6.1k Hz,five adjustable levels,a maximum time resolution of 0.6ms,seven adjustable levels,and a dynamic range of 67 d B.Time-frequency synchronization function,while supporting seamless switching of time-domain and frequency-domain modes.