| The flare process will generate a large number of high-energy electrons,and the problem of the acceleration mechanism of these high-energy electrons is a core issue of flare physics.At the same time,high-energy electrons moving toward the earth will threaten the safety of satellite equipment and astronauts in the earth space system.And it is one of the core elements of space weather disasters.The spectral intensity change of solar millimeter-wave radiation is highly sensitive to changes in the number and energy of high-energy electrons,and it is one of the important indicators for detecting the properties of high-energy electrons and conducting disaster warnings.Affected by atmospheric absorption and turbulence,emission in the millimeter-wave frequency regime(50-70 GHz)is mostly absorpted by the oxygen in the atmosphere and is difficult to carry out observations on the ground.Therefore space-based observations are demanded.So far,the space-based observation of the corresponding frequency band has not been realized at home and abroad,so the research on the space-based observation of this frequency band has important scientific significance and application prospects.The work of the paper is a preliminary proof-of-principle of the national major scientific research instrument development project of the National Fund Committee--space-based spectrometer of solar flares at millimeter wavelengths project applied by the Laboratory for Electromagnetic Detection,Institute of Space Sciences,Shandong University.The purpose of the paper is to explore the relationship between the solar radiation flux and atmospheric attenuation near the atmospheric absorption peak of 60 GHz.The others are to complete the construction and preliminary testing of the four-channel left/right solar radio spectrometer above 50 GHz,complete the outdoor solar observation experiment and make a preliminary analysis of the corresponding frequency band observation results.The work have provided preliminary theoretical support and technical accumulation for the smooth progress of this major scientific research instrument development project and also provides technical support for future joint observations of the sky and the earth(high altitude)near the atmospheric absorption peak of 60 GHz.The main research contents of this paper are as follows:(1)The observed parameters in the 50-70 GHz frequency band were calculated,and the general architecture of the system was determined.According to the solar microwave radiation theory,the quiet solar radiation flux of the corresponding frequency band is calculated,and the atmospheric attenuation and sky noise temperature of the corresponding frequency band are calculated according to the spectral line integral calculation method of the SKA document.The observation frequency band and down-conversion structure of the system are determined.The system parameters are calculated;the gain of the system is set to be about 30 dB;and the noise figure is about 3 dB,under the guaranteed gain fluctuation of 1%;the sensitivity in the two frequency bands is 11 SFU(Solar Flux Unit,10-22W/Hz/m2)and 31 SFU respectively.(2)The construction and simulation of the system link are completed.According to the observation frequency band and device investigation,the overall design scheme of the system is determined,and the RF analog front-end,ADC(Analog-to-Digital Converter)and MCU(Microcontroller Unit)parts are selected;the schematic diagram of the AD acquisition circuit board is drawn.Simulink is used to simulate the RF link and simulate the observation effect.The simulation results show that the quiet sun signal will cause a 3 dB signal rise in the 50.551.5 GHz frequency band,and the rise in the 53.5-54.5 GHz frequency band is so small that it is invisible to the naked eye.(3)The system host computer software platform are developed.Based on the MFC platform,the software of the host computer is developed,which realizes the functions of serial communication between MCU and PC,real-time image display,real-time storage,manual saving and curve clearing.After the software system is complete,the system is tested using the up-conversion test method,and the linearity of the receiver system is more than 0.99994,the linear dynamic range is 20 dB and the system gain is 25 dB.(4)A solar observation experiment was carried out and the results were analyzed.The single-channel and four-channel experiments were carried out respectively,and the quiet sun could be clearly observed.The experimental results in the 50.5-51.5 GHz frequency band were in line with the simulation results,and the quiet solar radiation flux intensity caused about 3 dB on the basis of the noise floor.In the 53.5-54.5 GHz frequency band,the experimental results show that the single-channel experiment and the four-channel experiment have a significant increase of 3dB and 1.2dB,respectively,which is quite different from the simulation results.In addition,the results of outdoor solar observation experiments on different days are not the same,and will be affected by the weather.The observation system is a ground-based principle prototype of 50-70 GHz spaceborne solar flare millimeter wave radiation detection spectrometer with a miniaturized receiver architecture.The ground-based observation of left/right rotation four-way quiet solar radiation flow in two frequency bands is realized.After testing,the linearity of the system can reach more than 0.9994,the average gain is 25 dB and has a linear dynamic range of 20 dB,which lays a foundation for the promotion of subsequent projects. |
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