Transmitter design for Visible Light Communication

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Supervisor:
Fekete Gábor
Department of Broadband Infocommunications and Electromagnetic Theory

In this paper I will give an overview of the advantages of Visible Light Communication (VLC) and I will mention some possible future applications. In addition I will discuss in more detail the comparison of the properties of the currently available light sources (such as light bulbs and fluorescent lights) and the LEDs used in visible light communication. Furthermore I will take those characteristics of the LED into account, that are trying to support the fact that in the future LEDs will play a decisive role both in lightning and communication.

Subsequently, I will give a brief overview of the harmful effects of visible light on living organisms. These dangerous impacts can come from different light emitting devices because our goal is to replace the radiating effect of the Sun with these light sources. However, it is important to bear in mind that these artificial sources emit a significant intensity of electromagnetic radiation that differs from the wavelengths of the Sun light, which radiation can be harmful for living organisms. I will mention some relevant experimental results referring to that.

Then I will present the circuit design project which was my task. The designed circuit can modulate the emitted light of the LED. The modulation form can be analogue intensity modulation or OOK. The modulation signal of the LED is provided by a signal generator. It is important to note that the various circuit elements such as transistors have a distorting, damping effect on the transmission in reality. Furthermore the disturbance sensitivity of the transmitted signal can not be ignored.

The aim is therefore to examine how the received signal detected by an optical detector deviates from the modulating signal. Based on the obtained results I draw conclusions from the visible light communication regarding to practical usability.

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