Body-Centric Wireless Communications: A Survey of Hearing-Instrument Antennas

A survey of hearing-instrument antennas used for body-centric wireless communications is presented. One challenge is to transmit a radio signal from a hearing instrument on one ear to a hearing instrument on the other ear to improve the hearing quality. Transmission through the head is not an option due to the losses at the ISM-band at 2.4 GHz. This is overcome by the use of surface waves, i.e., a wave that creeps on the top of the head. A major challenge is to construct antennas that effective launches surface waves for different types of hearing instruments.