Research On High-speed Ultraviolet Communication System Based On LED Array

Ultraviolet communication（UVC）is a new type of wireless optical communication,which transmits and receives information by the solar blind ultraviolet light.It has the characteristics of strong anti-interference,high secrecy,omnidirectional and non-line-of-sight communication.Consequently,as an auxiliary communication mode,it can be widely applied in the complicated situations.Subject to ultraviolet devices and the weakening of atmospheric channels,the transmission rate of current UVC system is low（less than 100 kbps）,which fails to meet the requirements for fast,accurate and high-volume communication.Therefore,how to achieve high-speed communication ranging from hundred kbps to Mbps,will be a key point in UV communication.In the support of the’973’plan of"Theory and Method of Wireless Transmission of Wide Spectral Signals"and"XX National Defense Scientific Research Project"sponsored by Science and Technology Commission of the Military Commission,this paper carried out the research and design of high-speed ultraviolet communication system.This paper first investigated and summarized the device selection,implementation and communication performance of the current UVC systems in detail,which will provide guidance for subsequent research.Then,we selected a 266 nm UV LED array with luminous power of 30m W as the emitter,and made a design for high-speed signal processing circuits in both transmitting and receiving side.Based on the electrical characteristics of UV LED array,a high-power and high-speed driver circuit was designed.Three-output parallel driving and constant current control mode were adopted to improve working stability of LED,and PWM modulation was used to load the driving signal.The results indicated,the output power of driving circuit was 10W and driving speed was up to1Mbps.Meanwhile,its accuracy of current error was less than 1.5%.Considering the characteristics of receiving signal in long distance,a two-stage differential preamplifier circuit was designed to achieve effective amplification,which also combined with inverter capacitance differential circuit to suppress DC drift.The circuit gain was up to 140d B and the overall bandwidth reached 1.92MHz.In addition,a signal preprocessing circuit was designed to realize secondary processing for the receiving signal.The high-frequency noise was filtered out by second-order low-pass filter.The binary processing was completed by comparator circuit,and the pulse signal was finally reconstructed by FPGA.According to the research results,we proposed and demonstrated a high data rate ultraviolet communication system based on UV LED array.Experiments were conducted to test the performance of the UV communication system under different testing conditions,including different transmission distance,communication rate,pitch angle and time period.Meanwhile,the influence of luminous power of the emitting source on the transmission distance is also explored.The testing results were further analyzed and summarized.And a testing for bit error rate（BER）was carried out finally.It is shown that the ultraviolet communication system has high data rate of up to 1Mbps and bit error rate of less than 10^-4with 20 degree pitch angle in 400m,which can beat the best record created by UV-LED communication system in terms of the transmission rate.