Performance Research Of Satellite-earth Downlink Phase Compensation Multi-aperture Receiver System Under Mixture-Gamma Distribution

In the satellite-ground downlink,the earth's atmospheric turbulence will affect the received optical signal,which mainly causes non-uniform fluctuations in the refractive index,thereby causing uneven and random changes in the amplitude and phase of the received signal light,resulting in a beam of light in the receiving spot Phenomenon such as expansion,light spot drift and flickering of the light intensity have seriously affected the performance of the system,such as bit error rate,and even caused signal interruption.In this paper,a phase-compensated multi-aperture receiving system is used to alleviate the link fading phenomenon and analyze the bit error rate performance of the system.In the analysis process,a new Mixture-Gamma(MG)distribution is used to approximate the turbulence model.In this paper,considering the problem of satellite-ground downlink fading caused by turbulence,the following researches are mainly carried out:Firstly,the model of the satellite-to-ground downlink phase compensation system is given.Next,the multi-aperture technology is introduced into the system,and the system probability density under the scheme of selective combining(SC),equal gain combining(EGC)and maximum ratio combining(MRC)is derived.Function(PDF)expression and its simulation analysis.The results show that the satellite-to-ground downlink phase compensation multi-aperture receiving system can improve the signal-to-noise ratio of the system and alleviate the fading of the received signal.Next,the advantages of the MG distribution compared to several classic turbulence models are analyzed and verified,and the distribution of the PDF of the signal-to-noise ratio under different turbulence models after the MG distribution is approximated is compared with the original distribution.Luo simulation method was verified,the results show that by changing the parameter expression in the MG distribution,the PDF and cumulative distribution function(CDF)after the MG distribution can be highly matched with the original distribution,and by calculating the mean square error(MSE)and KL dispersion Degree(DKL),which proves that the approximate accuracy of the MG distribution is higher than that of the classical model.Finally,using the MG distribution approximate turbulence model,the approximate expressions of the bit error rate performance of the satellite-to-ground downlink phase compensation multi-aperture receiving system under three different combining methods were derived,and the simulation comparison was performed using the Monte Carlo simulation method.Verification,the results show that the performance analysis results after using MG distribution approximation and Monte Carlo numerical simulation results are highly matched,and the phase-compensated multi-aperture receiving system can effectively reduce the bit error rate performance of the satellite-ground downlink,of which the MRC mode is the best.