A Visible Light Communication Experimental System Design And Implementation

The visible light communication(VLC)system is a communication system,where visible light media work as media,which is consist of visible light transmitting subsystem and visible light receiving subsystem.The wave-length of VLC system is far away from the wave-length of a conventional radio communication system,which results in less interferences between these systems,where it makes this a superiority.VLC system has much richer spectrum resource,and the feature of lighting makes it to be a multi-role—communication and lighting,which makes it more power efficient,comparing to the conventional radio communication system.The focal studies of this paper includes design and implementation of visible light transmitting subsystem and visible light receiving subsystem,and the vertification of the designed VLC systems.The main work of this paper is as follow:The main work of this paper includes designing a VLC transmitting subsystem.This VLC system is implemented by digital,which is consist of digital modulator,DAC(Digital-to-Analog Convertor)circuit,equalization circuit,amplifiers and full-differential current LED driving circuit.DSP modulates the digital bits into desired data to be sent.FPGA will add the frame header over the received data,at the same time,it will drive the DAC to send the desired data.The output of DAC will be equalized by equalization circuit to compensate the parasite low-pass of LED.The equalized signal will drive the full-differential current LED driving circuit,where the intensity signal will be spread into free space,realzing the signal transmitting.The main work of this paper includes designing and implementing a VLC receiving subsystem.The receiver of VLC system is consist of PIN-Tranimpedance amplifier circuit,two-stage voltage amplifiers circuit,anti-aliasing filter circuit,ADC(Analog-to-Digital Convertor)circuit,digital demodulator.PIN-Tranimpedance amplifier work as a transformer that converts the current to the weak voltage,which is produce by PIN diod.The two-stage voltage amplifiers will enhance the signal to get the level ADC can be detected.A low pass filter will filter the signal to avoid to be aliased.The signal detected by ADC will be transformed to FPGA.The digital demodulator is consist of DSP and FPGA.After the signal frame header is captured by FPGA,the following data will be saved to RAM in the FPGA,then DSP will finish the demodulation.After the system above is implemented,these key sub-modules will be tested and analysed in domain.After finishing the validation of these modules,DSP will send the random bits through the VLC,and it will be detected,demodulated,checked by the VLC system receiver.Finally,the performance of the VLC system will be figured out.