Ultra-low-power circuit techniques for mm-size wireless sensor nodes with energy harvesting

This paper describes circuit techniques for energy-harvesting technology in millimeter-size ultra-low-power batteryless wireless sensor nodes as a front end for BigData, IoT, M2M, and ambient intelligence. Power generated by energy harvester becomes as small as the nanowatt level when the size of a sensor node becomes millimeter-size. First, technical trends in low-power circuits and the portfolio of energy harvesting and circuit technology are discussed from the viewpoints of technical and application issues. Then, circuit techniques for nanowatt level wireless sensor nodes-a zero-power vibration sensing circuit, power management with MEMS switch, and an intermitted RF transmitter-are explained.