Research And Implementation Of Spot Location And Communication Multiplexing System Based On Four Quadrant APD

Laser communication technology has the advantages of high communication rate,strong confidentiality and no occupancy of radio frequency band.Today,with the increasing shortage of radio frequency band resources,it has broad prospects for development.However,the narrow laser beam,which must propagate along a straight line,also poses a challenge to the stability of the communication link.It is of great practical value to improve the performance of tracking system by improving the signal light detection technology and improving the signal accuracy.The main research object of this paper is the facula location and communication multiplexing system in laser communication precise tracking.The main parameters and principles affecting the positioning accuracy and communication rate are studied.The research results are validated and the system is designed.The main research work is as follows:(1)The laser detection principle of APD avalanche diode is studied and analyzed.The main parameters affecting the performance of APD,such as cut-off wavelength,responsiveness,dark current,multiplication factor,are summarized and calculated.Finally,the basic principle of four-quadrant APD detector as multiplexing device is analyzed.(2)The main parameters and their influencing factors of the spot positioning system and the communication system are studied.For the spot positioning system,sensitivity,dynamic range and resolution are selected as the system performance indicators.The influencing factors of the three factors are studied,and the appropriate parameters are basically determined.For the communication system,the bit error rate and communication rate are selected as the system performance indicators.The factors and principles affecting the indicators are studied.Based on this,the specific technical indicators of the system are designed,and the overall scheme of the system is determined according to the demand indicators.(3)According to the research results of system index and influencing factors,a set of spot location and communication multiplexing and forwarding system based on four-quadrant APD is designed.Compared with the traditional large-area low-rate system,although the detection area of this design is slightly smaller,the communication rate has been greatly improved,which is the main innovation of this research work.(4)The experimental results show that the communication error rate is less than 10-6power and the communication rate is 160 Mbps under the detection sensitivity of-30 dbm.The experimental results show that the dynamic range of the system is 0.5mm and the resolution of the spot location is 0.8rad.The communication rate can be greatly improved when the design requirements are met.