Research On Receiving Antenna And Synthesis Algorithm For Dynamic Solar Radio Observation System

Observations in the radio frequencies are critical to scientific studies in solar physics.Solar radio bursts,especially,the bursts in the wavelength range from metric to decametric,carry important information about eruptive processes in the solar atmosphere,formation and evolution of coronal shocks and distribution of energetic electrons,and they are essential to understanding of solar eruptions and relevant space weather application,and have important applications in forecasting the shock arrival time and solar energetic particles.Especially the circular polarization character helps to understand the trigger mechanism,energy release and transform,and motion of matter in the bursts.This paper studies the wideband and full polarization radio receiving system,developed the dual polarized wideband antenna with low cross polarization,proposed a digital circular polarization synthesis algorithm and beamforming algorithm,and realized the large dynamic observation of solar radio burst.The main work of this paper includes the following parts:Firstly,a radio receiving system for solar dynamic spectrum observation based on digital polarization synthesis and beamforming is proposed.Based on the needs of scientific observation,the system uses two orthogonal polarized wideband receiving antennas and arrays to synthesize multiple polarizations and beams in the digital domain,which solves the technical problems of wide receiving spectrum,multiple receiving polarization types,large beam scanning range and high observation accuracy.The system combines FPGA for real-time signal processing,The solar dynamic spectrum observation is fast,accurate and comprehensive.Secondly,in order to realize fully polarized spectrum observation,a paraboloid antenna fed by UWB dual polarization log periodic antenna is designed,and a polarization synthesis algorithm is proposed to realize left-handed and right-handed circularly polarized beams.Based on the simulated or measured results of antenna element,the algorithm compensates the amplitude and phase offset caused by antenna asymmetry,cross polarization and environmental interference in the synthesis process,and finally the linear polarized antenna is equivalent to circular polarized antenna.Thirdly,a dual polarized log periodic antenna array for radio observation and a circular polarization beam synthesis method are designed to realize left-handed and right-handed circular polarization beam scanning.Based on the designed dual polarization antenna array,an integrated algorithm of polarization synthesis and beamforming is proposed.Firstly,the dual polarization antenna is synthesized to two orthogonal circular polarized antennas,and then the multi-dimensional and multi parameter radio signal receiving model is established by using the circular polarization beam synthesis method to realize the dual circular polarization beam scanning.Finally,this paper presents an outdoor test method for large antennas and arrays,which is used to test and verify the radio receiving system based on digital domain polarization and beamforming.In this method,UAV is equipped with transmitting antenna and test signal source,combined with satellite positioning,which can measure the pattern and polarization characteristics of antennas and arrays,and solve the problem of large antenna performance index test in the actual use environment.A set of perfect and widely applicable large antenna calibration verification method is obtained;It is used to test and verify the radio receiving system in this paper.The array element pattern,polarization synthesis pattern and beamforming pattern are tested.The effectiveness of the polarization synthesis and beamforming algorithm based on digital domain is verified.Based on the measurement,the designed receiving system is used for solar radio observation,and the results are consistent with those of foreign stations.The radio receiving system of solar dynamic spectrum observation based on digital domain polarization synthesis and beamforming studied in this paper has important theoretical significance and application value for realizing the dynamic polarization observation of ultra wideband solar radio signal and improving the scientific value of data.The results have been applied to the practical observation of solar radio burst in the metric to decametric band.The observation results of the system are compared with the observations at the same time and the same frequency at the overseas stations,and the accuracy of the system observation is verified.