Pre-Compensation Of Beam Wander Effect Of Ground-to-Satellite Uplink Communication

Atmospheric turbulence is an important factor affecting the transmission quality of satellite-to-ground laser communication optical signals.The uplink laser beam emitted from the ground first passes through the atmosphere and then enters the free space for transmission.It is more severely affected by the atmosphere,which will produce beam wander effects and high-order beam distortion.The field intensity distribution is uneven.Since the area of the on-board detector is much smaller than the area of the light field,the position of the receiver will always change,resulting in power fluctuations,the system error rate increases,and the satellite receiver cannot compensate.At present,the international common uplink compensation method is that the ground terminal adopts multi-aperture transmission,and the uplink beam is transmitted through multiple apertures,so that the beam is transmitted through different paths,thereby averaging the received power of the on-board terminal receiver and reducing the on-board.The terminal receives the fluctuation effect of power.However,for high-speed uplink communication signal light,the signal light emitted by the multi-aperture cannot be time-coaxial due to the optical axis of the transmission position,which may cause the uplink optical signal bit to be synchronously reduced,which may affect the uplink laser transmission.In this paper,we will analyze the pre-compensation measures for atmospheric turbulence in the ground transmitting antenna,and detect the wavefront of the atmospheric channel through the downlink adaptive optics system,and then adaptively pre-compensate the uplink transmitting beam to reduce the beam wander effect of the satellite-to-ground uplink beam.High-order distortion effects improve uplink communication quality.Since the uplink and downlink laser transmissions are different through the path of the atmosphere,the instantaneous effects are different.The effects of atmospheric turbulence are considered as the total cumulative effects during the study,and only the phase changes of the initial position and the final position are considered.The main research work of this paper is as follows:1.Study the nature of atmospheric turbulence and understand its basic model.Then,a series of macroscopic effects brought about by atmospheric turbulence are analyzed.According to different atmospheric models,the principle and formula corresponding to the macroscopic effect are obtained,which is convenient for verifying the established laser transmission model.2.Using the phase screen simulation method to obtain the phase information received by the downlink downlink,the Zernike polynomial method is used to solve the distortion phase from the low-order to the high-order coefficients,and compensated by the mode method.This is used as the phase compensation information for the uplink of the satellite.3.Establish a model for uplink transmission of satellite lasers affected by atmospheric turbulence,verify the correctness of the model with existing theories and formulas,and then pre-compensate the uplink to observe the pre-compensated light field and beam wander variance.Analyze the effect of compensation.4.Using the OOK modulation method,analyze the relationship between the order of compensation and the bit error rate to obtain a suitable compensation order.Under the pre-compensation conditions,the parameters of the uplink communication of the satellite are analyzed.Completion of the pre-compensation study of the uplink beam wander effect of the satellite.