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The feasibility of energy harvesting using the human body, which is used instead of a general antenna as an antenna in a low-frequency band to harvest energy included in an ambient electromagnetic wave, is investigated. Using the presented method, it is possible to harvest much more power in comparison with that possible with the previous method, in which a general antenna is used to harvest power in the high-frequency band. Also, this method can be easily applied to mobile devices because no antenna is required.
Introduction: The operating time of mobile devices such as smart phones and tablet PCs is mainly limited by the capacity of their batteries, so energy harvesting has been studied to harvest energy from external sources (e.g. solar power, thermal energy, and kinetic energy from physical activities) and provide the harvested energy to mobile devices.
An ambient electromagnetic wave is a good candidate for a harvesting source. In a general environment, electromagnetic waves are radiated intentionally for communication from signal transmitters or emitted unintentionally from various electronic devices [1]; the energy included in an ambient electromagnetic wave can be harvested by receiving a radiated or emitted electromagnetic wave using an antenna. Several researchers have studied antennas for energy harvesting from an ambient electromagnetic wave [2-4]. A spiral antenna was designed to receive radiated electromagnetic waves over a wide-frequency range from 1 to 3 GHz [2]; however, its size was too large for the antenna to be integrated with a mobile device. A small-sized antenna operating at 300 MHz was developed [3], but it is still not easy to find sufficient additional space in compact mobile devices to integrate the antenna. For every signal transmitter and electronic device, its radiation or emission level of electromagnetic waves is regulated according to various regulations. The regulation level is generally higher in the low-frequency band under 30 MHz than in the high-frequency band [5, 6], so much more energy can be harvested at the low-frequency band. Energy harvesting from a local AM station at 1 MHz was studied in [4], but any antenna that is to be operated at such...