Design And Implementation Of Several Modules Based On Fpga In High-order Space Coherent Optical Communication Systems

Space optical communication system with high data rate,high spectral efficiency,high security,strong anti-interference ability and other advantages,has gradually become the space field of communication research hotspot.Digital coherent optical communication technology for signal transmission process of the introduction of the injury in the electrical domain,using DSP algorithm for damage compensation with high receiving sensitivity,and achieved by using higher order modulation technology to further expand the channel capacity in the long-distance,non-relay transmission in a wide range of applications.The use of higher order modulation formats combined with DSP algorithm is to achieve highspeed,long-distance free-space coherent optical communication system of effective technical means.Currently,the free-space channel in real time DSP algorithm research is rare,and therefore for the space coherent optical communication system designed for easy hardware implementation of parallel real-time DSP algorithm has important research value.This object-oriented Quadrature Phase Shift Keying and Quadrature Amplitude Modulation free-space coherent optical communication system real-time DSP algorithm design and implementation,the main research contents are as follows:(1).Based on FPGA chips,the two-stage high-precision parallel phase estimation algorithm of QPSK designed to implement.For the residual frequency offset effects and traditional Viterbi-Viterbi algorithm implemented in hardware resource utilization rate is high,build a system,which proposed based on the Viterbi-Viterbi algorithm of the highprecision phase estimation parallel algorithms and FPGA design of the program,the algorithm implementation process is optimized,further reducing resources.Build offline system simulation platform of the proposed algorithm is validated,the design of selected two-stage symbol block length,respectively 24 and 128.Experiments show that,effectively reduce resources under the conditions of this algorithm compared with the traditional algorithm with greater frequency offset tolerance.Build 2.5G Baud QPSK free-space coherent optical communication system.Experiment results show that the weak turbulence conditions the algorithm in-47dBm to-44dBm received optical power of the bit error rate of less than 1E-3 magnitude,the offline experimental performance is similar.(2).Based on FPGA chips,the parallel phase estimation algorithm of 16QAM designed to implement.Higher-order signal constellation points has smaller distance,the phase noise is more sensitive to the characteristics.Combined with the problem of hardware implementation requirements,is proposed based on the QPSK lap algorithm with high accuracy and low complexity of the parallel phase estimation algorithm and FPGA implementation of the program,the introduction of the absolute value of the replacement four square design,significantly reduce the algorithm complexity and resource utilization.Off-line experimental verification shows that under the condition that the received optical power is-33dBm,the error rate is lower than the 1E-3 volume level,meeting system requirements.(3).Based on FPGA chips,the parallel digital clock synchronization algorithm of 16QAM designed to implement.High complexity of clock synchronization algorithm for 16QAM signals,the FPGA chip operating frequency of the high requirements.The design of share-based numerical controlled oscillator low-complexity parallel digital clock synchronization algorithm and FPGA implementation of the program,effectively reduce resources.Off-line experimental verification shows that under the condition that the received optical power is-32dBm,the error rate is lower than the 1E-3 volume level,meeting system requirements.