Design And Implementation Of Underwater Blue Light Digital Transmission System Based On Gallium Nitride LED

As a emerging of technology,visible light communication technology continues to progress with the development of the LED industry.Visible light communication can be used as an important technology for underwater communication.At present,underwater communication is usually based on sonar technology,which is limited by the limitation of sound waves that the large propagation delay and low transmission rate.With the advantages of high transmission rate and low link delay,visible light communication can solve the problem of high-speed transmission in short underwater distances.This paper starting from photonic devices,a blue light-emitting diode is designed on a commercial sapphire-based Ga N epitaxial wafer by flip-chip technology,and the design process of the LED is briefly described and the electrical properties,optical properties,and communication performance of the designed light-emitting diodes are measured,according to the obtained parameter performance,the appropriate circuit design scheme and the related chips are selected.Secondly,the appropriate modulation scheme is selected through theoretical analysis and comparison.In order to facilitate bit synchronization and reduce the complexity of system design,this paper selects the 2FSK modulation scheme,and uses Matlab to simulate the designed modulation scheme to verify if the modulation and demodulation algorithm are correct;use Optisystem optical simulation software to build a visible light communication system based on 2FSK modulation,observe possible problems during transmission of the system through simulation and give corresponding solutions;design and realize the LED drive circuit with automatic voltage adjustment;design low-noise,high-bandwidth receiving circuit;FPGA is used as the main control chip of the system to realize the driving of the audio codec chip,the acquisition and processing of data signals,the 2FSK modulation and demodulation,and to verify whether the code function meets the design requirements through functional simulation;in order to reduce the volume of the system,through reasonable chip selection and circuit design,the entire system circuit is designed on two circuit boards,each circuit board’s area is 5cm x 5cm,finally design and implement a real-time,high-efficiency,small-volume visible light digital audio transmission system.The data test result in this paper shows that the Ga N LED supports 8Mbps PRBS data transmission.In the system,the power consumption of a single LED is 210 m W and the highest working voltage of the whole system is 5V.The power supply mode is 2～4 18650 lithium batteries;when the system uses a single LED as the emission source,the audio sampling rate is 8 KHz,and the2 FSK modulation output the square wave of frequency is 500 KHz and 1MHz,this system can achieve an atmosphere of 8m,an ordinary water tank above 70 cm for audio data transmission.