| The free space quantum communication uses the space laser channel to transmit the quantum information.The laser beam divergence angle is small,so it needs Acquisition,Tracking and Pointing(abbreviated as ATP)system to establish and maintain the communication link.The development of space quantum communication is moving towards the integrated network of the earth and the universe,and the development of high orbit quantum satellite as a communication relay will be the only way.The far link distance between the high orbit satellites and the ground stations calls for higher requirements for the tracking accuracy of the ATP system.Based on the ATP technology of the low orbit quantum satellite “Mo-Zi”,the system analysis and engineering practice optimization from the mechanism are one of the feasible solutions for the development of the higher precision ATP system.This paper takes the space ATP system of quantum communication as the research object,and the key technology for ATP system with ultra high tracking accuracy is studied.The accuracy of the compound axis ATP system is determined by the fine tracking system,so the fine tracking system has become the focus of this research.The main work of the paper includes: The working principle of the ATP system is introduced,including the working process,the system structure and the aiming scheme,and the key parameters coupling relation of the system is analyzed,and the precision tracking system is introduced.Based on the analysis of tracking and pointing error of ATP system,a detection system based on diffraction spot sampling is proposed,and the optical parameters of fine tracking system are optimized.The aberration relation between the off-axis optical system and the coaxial optical system is derived based on the Zernike polynomial,and the influence of the optical aberration on the receiving optical axis and the emission axis of the off-axis optical system is simulated and analyzed.The non-ideal characteristic factors of the area array detector are analyzed.The influence of various factors on the spot location is simulated and analyzed,and the detector non-uniformity correction is implemented.Based on the fine tracking control system,the influence of control resolution on tracking accuracy is explored through comprehensive simulation analysis and experimental test.The main innovations of the paper are as follows:1)The detection system of diffraction spot sampling is studied.The comprehensive influence of wavelength,system focal distance,telescope diameter and detector's effective pixel size on the location of diffraction spots is analyzed,and the spatial sampling relation must be satisfied for the precise position detection.Based on the spatial and frequency analysis of the diffraction error of diffraction sampling,the optical system parameters are optimized for the precision tracking system.The experimental results show that when the spatial sampling relationship is satisfied,the precision of precision tracking is increased from 0.44 ?rad to 0.12?rad.2)The influence of aberration of optical system on the optical axis deviation of receiving and transmitting is studied.Based on the aberration fitting of Zernike polynomials,the influence of the aberration on the optical received axis and the transmission optical axis of the optical system is analyzed.Numerical simulation results show that,in order to make the optical axis calibration accuracy better than 0.1?rad,the quality of the coaxis optical systems need to be better than ?/30 RMS,and quality of the off-axis optical systems need to be better than ?/100 RMS?3)The influence of detector's non ideal characteristics on spot location is studied.A mathematical model is established to analyze the influence of random noise and filling rate of different detectors on the location accuracy of spot,and get the best spot radius under different filling rate.The effect of strip noise on the location of the spot is analyzed.The simulation and experimental results show that the location deviation of the spot along the extended direction of the noise is greater than that in the orthogonal direction.The non-uniformity of the response of the detector is corrected and analyzed.The experimental results show that the maximum deviation of the spot location of the spot 0.08 pixel converges to less than 0.05 pixel after the non-uniformity correction.4)The influence of system control resolution on tracking accuracy is studied.The disturbance suppression ability and tracking accuracy of the fine tracking system under different control resolutions are analyzed and verified by experiments.The experimental results show that when using the 16 bit quantization DAC,the tracking accuracy is increased from 0.5016 ?rad to 0.4128?rad compared with the 12 bit quantization DAC.Spectrum analysis shows that if we want to further improve the tracking accuracy,we need to further increase the system's bandwidth of disturbance suppression.Theoretical and experimental results show that when the design of optical system to satisfy spatial sampling relationship,and the optical system quality is superior to 1/30 ?RMS in coaxial(off-axis optical system corresponding to 1/100 ?RMS),and doing the non-uniformity correction of detector,and the instantaneous field of view of a single pixel is less than 1?rad,And the tracking control resolution is improved to 16 bit quantization.The tracking accuracy of the system can be raised from the current 0.5?rad magnitude to less than 0.1?rad. |
PDF Full Text Request