A Wireless Motion Sensor Operating Down to -28dBm Energy Harvesting

ZeroPower devices are the next generation of Internet of Things. Typically taping from ambient energy, or activated by a remote reader, their first and foremost challenge is the operation distance from the nearest RF source. Unfortunately, these systems can only be activated within a range of a few tens of meters due to their minimum activation power (also named reading sensitivity). This work reduces the harvesting power to a new threshold of -28dBm (1.5 μW). We demonstrate a wireless motion sensor operating in burst mode with as low as 120 mV of DC voltage and 0.72 μJ of stored energy. This efficient operation is achieved without any DC/DC conversion thanks to a four-stages rectifier biasing a tunnel diode Voltage-controlled oscillator (VCO).