This paper presents a wireless charging method based on textiles through harvesting and storing energy from human movement. The proposed method uses resonant coils made of a conductive yarn and a flexible printed circuit board. The conductive yarn consists of polyurethane-coated copper and polyester filaments. The transmission characteristics of the resonant coils, which were worn on the arm of a human body, were evaluated using simulation and measurement tools. It was determined that the change in the resonant frequency of the conductive-yarn resonant coils can be obtained from the coil length, stitch intervals, and fabric thickness using equations. The measured resonant frequencies of the sending and receiving coils were designed to achieve a resonant frequency of 13.56 MHz when the coils are worn. The resonant coils were worn on the arm of a subject, who moved at various speeds, and the transmission efficiency was measured using an alternating current–direct current converter. The measurement results showed a maximum transmission efficiency of 55.1%, even though the resonant coils were worn around the arm and not the leg, and an average transmission efficiency of 52.1% when the subject was moving at a speed of 6 km/h.

Human body communication method technology can transmit the data signal through human body that is suitable for healthcare and mobile devices. This technology uses the human body channel and therefore is greatly influenced by human body characteristics. Impulse response measurements were performed on 120 adult males to analyze channel characteristics of human body. The average signal loss was −67 to −65 dB depending on the transmission direction. In addition, the correlation between human body channel characteristics and body weight, skeletal muscle mass, body fat mass, total body water and transmission and reception direction signal loss were obtained. Through analysis of channel characteristics of human body medium, channel characteristics suitable for human body communication device are presented.

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