Experiment on battery-less sensor activation via multi-point wireless energy transmission

This paper presents an indoor experiment to verify the battery-less sensor activation via multi-point wireless energy transmission with carrier shift diversity which realizes seamless coverage extension of the sensor activation. The multi-point scheme is employed to overcome path-loss attenuation. The carrier shift diversity has been developed to achieve uniform coverage of power transmission by combating standing-wave problem caused by multi-point transmitters as well as multipath waves, while its effectiveness on activation of battery-less sensors has never been studied in real environments. In this paper, we develop prototype hardware of battery-less sensor and conduct an indoor experiment with the developed sensor node. The experimental results show that the coverage of single-point and simple multi-point wireless energy transmission are limited at 44% and 70% respectively, while that of the proposed multi-point wireless energy transmission with carrier shift diversity achieves 100% to activate the developed sensor node which consumes −4 dBm for a transmission period of 1s.