Visible Light Optical Camera Communication for Electroencephalography Applications

Due to the cable-free deployment and flexibility of wireless communications, the data transmission in the applications of home and healthcare has shown a trend of moving wired communications to wireless communications. One typical example is electroencephalography (EEG). Evolution in the radio frequency (RF) technology has made it is possible to transmit the EEG data without data cable bundles. However, presently, the RF-based wireless technology used in EEG suffers from electromagnetic interference and might also have adverse effects on the health of patient and other medical equipment used in hospitals or homes. This puts some limits in RF-based EEG solutions, which is particularly true in RF restricted zones like Intensive Care Units (ICUs). As a recently developed optical wireless communication (OWC) technology, visible light communication (VLC) using light-emitting diodes (LEDs) for both simultaneous illumination and data communication has shown its advantages of free from electromagnetic interference, potential huge unlicensed bandwidth and enhanced data privacy due to the line transmission of light. The most recent development of VLC is the optical camera communication (OCC), which is an extension of VLC IEEE standard 802.15.7, also referred to as visible light optical camera communication (VL-OCC). Different from the conventional VLC where traditional photodiodes are used to detect and receive the data, VL-OCC uses the imaging camera as the photodetector to receive the data in the form of visible light signals. The data rate requirement of EEG is dependent on the application; hence this thesis investigates a low cost, organic LED (OLED)-driven VL-OCC wireless data transmission system for EEG applications

A study on dc-dc resonant switched-capacitor converters for LED driving and one application as a VLC transmitter

This work presents a family of Resonant Switched Capacitor (RSC) dc-dc converters operating as both high efficiency power converter and fast-response data transmitter for Visible Light Communications (VLC) applications. By operating under soft-switching, the topologies allow for higher switching frequency and higher slew rate, so that the VLC functionality can be embedded into the power stage without an auxiliary switch, which it is a major efficiency bottleneck for higher transmission rates due to its inherent hardswitching operation. This justify new efforts in enabling Pulse-Based Transmission (PBT) without this additional switch. Seven fast-response resonant converters are presented in this work, implemented with a proposed Switched Capacitor Cell and inspired on classic DC-DC topologies (Buck, Boost, Buck-Boost, Flyback, Cuk, SEPIC and Zeta). A 10 W prototype was built to demonstrate such feasibility, operating at a switching frequency of 500 kHz, resulting in nominal efficiency of 85% during data transmission under VPPM scheme, achieving up to 100 kpbs for various brightness levels, over a distance up to 1 m. Given the switching frequency conditions, this prototype is realized using GaN-FETs and Schottky diodes.-CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superio