Design And Implementation Of Wireless Optical Audio Communication System

Audio processing and transmission technology has been quite mature, moreover,the high standard and quality of audio equipment become basic requirements based on the flourish of intelligent hardware and IC industry. Wireless optical communication not only combines merits of wireless communication with optical communication, but also solves the problem brought by limited spectrum resources efficiently in radio frequency communication. Wireless optical communication has the characteristics of high bandwidth, anti-interference and high security. The combination of wireless optical communication and audio transmission has broad application prospects.Wireless optical audio transmission has obvious advantages, especially under some radio frequency communication vulnerable environment.This thesis develop a wireless audio optical communication system scheme, and then complete the hardware implementation of the transmitter and receiver which combines with the existing resources and test environment characteristics after theoretical researching on the subsystems of the audio transmission system of wireless optical referring to a large number of domestic and international documents about wireless optical communication fields, and studying in-depth the principle and mechanism of existing systems.The specific implementations include:1. Using FPGA to implement interface circuit of audio chip WM8731. WM8731 has audio control interface and digital audio interface, the interface circuit based FPGA controls the audio control interface of WM8731 by I2 C bus and communicates with the digital audio interface in DSP format.2. Design of laser driver circuit and photoelectric detection circuit board. The transmitter and receiver make use of intensity modulation/direct detection.The driver circuit of 650 nm laser based on MAX3263 has the function of automatic temperature and power control; the circuit based on PIN photoelectric detection AD8015 and AD807 has the function of photoelectric conversion, signal amplification and signal reduction.3. Using FPGA to implement OOK modulation and demodulation circuit. The system makes use of OOK(On-Off-Key) to finish signal modulation, meanwhile, it uses central insert Barker code and tri-state judge to realize frame synchronization,and uses a new method of digital PLL to realize bit synchronization.Finally, this thesis build up the communication system to have a overall test, it uses Signaltap II to conduct the online logic verification and uses oscillation to analysis the waveform of laser circuit of transmitter and receiver, moreover, conduct continuous test of audio transmission in normal weather. The test result indicates that the system can complete stable and high-fidelity audio transmission at 10 Mbps, which means the proposed communication scheme is reasonable and feasible.