| Summary: | 碩士 === 國立臺灣科技大學 === 光電工程研究所 === 103 === Due to the high potential of using micro-projection technology for porta-ble device application, it is expected that high-speed visible communication technologies based on the light sources of micro-projector will be integrated into the architecture of micro-projection. In distinguished with the conventional white light LED which is composed of blue LED and phosphor, this research intends to implement an experimental short-range high-speed visible light communication (VLC) system based on the use of RGB-based LED which has widely employed as the light source in micro-projector.
In order to understand the luminous efficiency of RGB-based LED, this research started with the optical characteristic measurement by using integrat-ing sphere. Since the data transmission rate of a VLC system is majority domi-nated by its modulation bandwidth, the fundamental bandwidth of RGB-based LED was measured under a fixed driving current of 350 mA. A first-order RC post-equalization approach was thereafter investigated to improve its modula-tion bandwidth. From the measurement results, it is clear that the modulation bandwidth of Red, Green and Blue LED with the use of a designed 1st order RC post-equalizer has improved from 6 MHz to 66.5 MHz, 15.5 MHz to 56 MHz, and 13.5 MHz to 66 MHz respectively. The total system modulation bandwidth with the use of a designed 1st order RC post-equalizer has improved from original 35 MHz to 188.5 MHz.
Finally, digital modulation techniques (NRZ-OOK and 4-PAM) with the use of a designed 1st order RC post-equalizer were employed to explore the data transmission rate. The system BERs were evaluated through the eye-diagram measured from Oscilloscope. The results shown that with the use of a designed 1st order RC post-equalizer, an aggregative data transmission rate over 500 Mb/s at a BER of 10-3 can be achieved by using NRZ-OOK modulation technique without any offline signal processing which is slightly better than 4-PAM, a more complex offline signal processing is required in order to recovery the received signal at a satisfied BER.
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