Investigation of LED driver circuits for visible light communication

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Fekete Gábor
Department of Broadband Infocommunications and Electromagnetic Theory

In my thesis, I am investigating visible light communication, especially the transmitter circuits used in this field of communication. I introduce several applications of visible light communication (from now on: VLC), e.g.: underwater communication based on VLC, indoor positioning using VLC, etc. In this thesis, I recapitulate the latest research results of VLC, and compare VLC to radiofrequency- and infrared-communication. I present the benefits and disadvantages of VLC, and also the theoretical limits of this technology (highest data-transmission speed, highest coverable distance). I also cover the basic system structure of the receiver-end circuits and thoroughly present the transmitter-side circuits used in VLC. I investigate three types of transmitter circuits, three transistor-based, a Bias-Tee based, and an active voltage-to-current converter based transmitter circuit. I build up the schematics and simulations for these circuits, and also build them onto printed circuit boards. I compare the measurement's results and the simulation results on various frequencies. I am using an EOT-2030A optical detector for the receiver-end, and show the waveform results of these measurements. In the end, I summarize all the advantages and the disadvantages of all the investigated circuits, and propose some further improvement possibilities for the circuits. And I also suggest a different approach for choosing the light source of the transmitter circuits.


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