A Multifunctional Sensor Node Sharing Coils in Wireless Power Supply, Wireless Communication and Distance Sensing Modes

This paper proposes a multifunctional sensor node that shares coils for wireless power supply (WPS), wireless communication, and distance sensing functions to pursue a small volume implementation. The sensor node has two coils inside, which are used as an antenna in WPS mode and wireless communication mode. In distance sensing mode, on the other hand, the two coils are used as electrodes to radiate an electric field to neighboring nodes. For switching functions, a normallyon junction type FET (JFET) is introduced so that the node automatically enters into the WPS mode when no energy is left in the node. We evaluated the functionalities and performance of each mode with a prototype. Experimental results show that, in the WPS mode, the two coils are automatically connected to each other, and the node can receive power even if there is no energy left in the node. In the wireless communication mode, 1 kbps communication is possible at a distance of 10 cm. Also, the distance can be measured at a range of 30 mm or less by using two coils as electrodes.