Wireless Communication System Based On UV Laser

The working wavelength range of UV communication system is200nm~280nm,UV communication gets widespread concern and attention because of itsconfidentiality, anti-interference ability and, it has the potential military applications.Ozone in the atmosphere and other particles will make strong absorption andreflection effect on ultraviolet, so there is little ultraviolet near the ground which can’tproduce background noise. By analyzing the atmosphere absorption and scatteringeffect of ultraviolet describes main factors that affect UV communication system. Thispaper discusses the characteristics of the LOS communication link. Also discussesNLOS communication by building ellipsoidal coordinates and Monte Carlo algorithmmodel and establishes the theoretical basis of the NLOS communication within acertain range.The key of UV communication system is how to select the device. By analyzingthe overall framework of communication system, UV laser is chosen as the light sourceand photomultiplier tube as photodetector, and developed a photodetector readoutcircuit and signal processing circuit.After the laser output pulse characteristics are analyzed and traditional FSKmodulation is studied, this paper make a new improvement by transmitting signal withadjustable duty cycle square wave.The receiving side demodulates the communicationsystem by counting ultraviolet pulses. In order to improve the accuracy of thetransmission system, the transmission channel needs coding. CRC code is selected ascoding method. Also selecting the FPGA as hardware platform, compared to traditionalsingle-chip technology, the performance of FPGA is better. This paper chose QuartusⅡ software and Verilog HDL language to design electric circuits and program.The experiment platform of UV communication system was built after theemulation of various modules. The experiment is carried out in different locations andat different times. Bit error rate and is counted and analyzed. Finally, a UV lasercommunication system is achieved whose communication distance is150m by dayand220m in the night, transfer rate is0.6Kbit/s, the error rate less than10-5.this UVsystem achieve the desired design requirements. At last, the paper makes a summary ofsystem design and points out future work prospects.