Research On Carrier Recovery Technology Of Spatial Coherent Light Array Signal

Space laser communication has become an important means for people to explore space resources and transmit space data,laser detection has become one of the important communication methods for space exploration.Spatial coherent optical communication uses laser beam as the carrier,which has the advantages of high power,fast transmission rate and large capacity.Coherent detection is also favored due to its high sensitivity and the diversity of modulation modes.This thesis mainly studies the coherent detection carrier recovery and antenna selection:1.For different turbulent channel models,this thesis simulates the influence of lognormal turbulent channel model on the received signal constellation diagram in coherent optical system and the bit error rate performance of coherent optical diversity receiving system under gamma-gamma turbulent channel model.The bit error rate performance of MRC,EGC and SC systems with different number of antennas and the bit error rate performance of single antenna are compared.The simulation results show that the MRC has the best performance when the signal noise ratio is high,the SC has better performance when the the signal noise ratio is low and the number of antennas is small.2.There is a GHz frequency difference between the transmitter and the local oscillator.Due to the turbulence,the fading of each antenna is different,so the the signal noise ratio of each received signal is different.In this thesis a method of optimizing the weights is proposed to make the branch with high the signal noise ratio have higher weights and the branch with low SNR have lower weights.Finally,the weighting makes the estimation of multi-frequency offset more accurate.The linewidth of the local oscillator laser can cause a large phase noise,this thesis proposes a single channel based multichannel phase noise estimation algorithm,weighted joint estimation in the turbulent channel,the simulation results show that the estimated value is more accurate and the system has lower bit error rate,at the same time,the system has smaller amount of computation.3.Considering time delay and other factors,a phase alignment algorithm for joint estimation of phase noise is proposed.Based on the SIMPLE and SUMPLE algorithm,the weighted phase of the SUMPLE algorithm is compensated after removing the phasenoise,so as to improve the performance of the synthesis.In addition,due to the influence of different fading channels on each antenna,the performance of all antenna combinations is not as good as that of several signal combinations with less fading.Therefore,the combination of adaptive system is used to select and synthesize the antenna to achieve joint estimation of phase and adaptive selection.The algorithm is improved by combining SIMPLE and SUMPLE algorithm.On this basis,a SIMPLE and SUMPLE joint estimation system is proposed in this thesis.When the number of antennas is large,the simulation results show that the antenna adaptive selection can meet the reliability transmission requirements of the system and the computational complexity is greatly reduced.