Research On Detector Array Diversity Reception Technology Of Atmospheric Laser Communication System

Intensity fluctuation that caused by atmospheric turbulence attenuates the energy beam of light seriously and reduces the quality of the communication. The use of the detector array diversity reception technology can reduce the atmospheric channel attenuation and improve communication efficiency. The size of the detector’s aperture is in inverse proportion to the values of sensitivity. Detector array diversity reception technology can achieve high sensitivity receiving, large effective area of detection and improve power gain. APD has higher sensitivity because carriers generated internal gain hundreds of times by the avalanche effect and it is the ideal device for atmospheric laser communication system.On the designing of the combining circuit unit, Signals are amplified primarily by the preamplifier with low noise, high bandwidth in the first place. Then, the signal is carried out linear amplification by the main amplifier. The signal is shaped and filtered by Schmitt flip-flop. Multiple signals are combined with FPGA technology. Finally, Clock signals are recovered with a phase-locked loop(PLL) technology and the data is decoded.Receiving combining is the key technique of the detector array diversity reception system. In two detectors diversity reception, SNR improvement factor of Maximal Ratio Combining increased100%,78.5percent raise for Equal Gain Combining and50%for Selection Combining relative to the traditional method. Through theoretical study and simulation, the performance of Maximum Ratio Combining is best but most complex. Selection Combining is worst while easy to implement and cheapest. Equal Gain Combining is in common. According to the system performance, the proper combining methods will be selected.Through above analysis, the paper provides a theoretical basis for designing the detector array diversity reception system.