A batteryless optical-wireless system with white-LED illumination

Abstract

A self-powered optical-wireless data-transmission system that uses solar cells and works under white-LED illumination is described. Solar cells have both power-generation and photodetection functions. Digital light modulation based on Manchester-NRZ pulses transmits data without flickering of the illumination. An instantaneous-activation 0.5-V CPU scheme with multi-threshold (MT) CMOS/SOI technology accelerates the clock frequency and shortens the active time, making ultralow-power operation possible. An electrical double-layer capacitor, which is a sub power source for the CPU in the active mode, also contributes to achieving self-powered operation. To verify the effectiveness of the optical-wireless system, we fabricated a wireless message board. The board shows that the system transmits data of up to 100 Kbps without a battery.