Study On Several Key Issues Of Transmitting And Receiving Antennas Of LED-based Indoor Visible Light Communication

The indoor visible light communication is an environmental friendly technology that can compound the lighting and the LED communication together. As a result, it is practically convenient and economic. The wireless optical communication technology has a promising application for its original advantages in many fields. Recently, the application fields of this technology have been broadly extended from the military and aerospace use to the civilian areas. The wireless optical communication technology has been developed and optimized. One only needs to remake the existing illumination system to realize illumination and communication. In this way, it can save the cost. Comparing to the traditional communication way, this technology has a much less cost, a wider area covering and a much safer mechanism without radiation.The transmitter and optical receiving antennas of indoor visible light communication are the main equipment of VLC system. Their qualities directly affect the reliability and stability of signal transmission of the whole communication system, so the LED light source and the optical receiving antenna have become the key to the research and design.This article starts from the transmitter of VLC system. First, it gives an introduction and analysis on the structure of LED light source in detail, LED light-emitting principle and signal driver circuit. Second, the channel transmission model of VLC system is introduced in detail, and the impulse response and channel noise distribution of the line-of-sight(LOS) link and non-line-of-sight(NLOS) link are analyzed and discussed.The illumination model of indoor LED has been established. The indoor illumination distribution is calculated. The antenna design of multiple linear arrays is used in order to meet the demand of indoor lighting. The influence of the different ways of LED light source array on indoor illumination distribution is analyzed. Finally, the optimal design model of the LED light source array is constructed. It achieves the uniform distribution of the indoor illumination and communication signal and realizes the whole distribution without blind area.The paper researches Fresnel lens from the classification and the principle of structure design of Fresnel lens. Fresnel lens has the effect of convergence and dispersion. As a result, the optical performance of the optical receiving antenna based on the Fresnel lens is analyzed. The concentrated ratio, light-gathering efficiency, the diffraction efficiency and spectral resolution are researched in theory. Based on the above theory of Fresnel lens, the model of Fresnel lens is designed and the optical performance of Fresnel lens is researched using the simulation software. The reasonable reference datum of the convergence and the dispersion are given. So the Fresnel lens optical receiving antenna can have good focusing effect, and it can also realize to divide the visible light into red, green and blue. Thus the Fresnel lens optical receiving antenna enhances the receiving efficiency of the optical signal, reduces the requirement of the detector, saves the cost and simplifies the system structure.