Design of a Matching Circuit for Energy Harvesting From a Hydrophone for Internet of Underwater Things

The Internet of Underwater Things (IoUT) refers to a network of underwater devices equipped with electronics, software, sensors, actuators, and network connectivity. A key technology for the IoUT is energy harvesting to extend operating time, for example, by using piezoelectrics to harvest energy from ambient noise or from self-motion where the input voltage is low and the spectrum varies. In this article, for such types of sources, we describe an electronic circuit designed to increase the efficiency of such energy harvesting by adapting it to the dominant frequency of the input signal. Our circuit consists of three units, a matching network, a rectifier, and a booster, each of which has a novel design and is tuned to the low frequency range (10 Hz–10 kHz) and the high frequency range ($>$10 kHz). A switching mechanism based on processing the input signal toggles between the two units. As we show from simulations and results of a hardware implementation, adapting the operation of the circuit to the instantaneous frequency significantly improves the efficiency of energy harvesting. Tests using a hydrophone as an energy harvesting sensor showed the obtained power efficiency is 80%.