An on-body antenna for control of a wireless prosthesis in the 2.45 GHz industrial scientific and medical frequency band

Abstract

Electronic prostheses require a communication link to other on-body nodes, for example, for control signal extraction. This link can be made wireless to improve user experience compared to wired solutions. Even though ample on-body communication techniques have been described for wireless body area networks, in prosthetics, the efficiency of wireless links is often neglected, in particular when radio frequency (RF) antennas are used. This work aims to show the benefit of on-body RF antenna design for prosthetics, by developing a dedicated antenna for use in a lower arm prosthesis. Additionally, this work tries to fill a gap in literature, where some antennas for dedicated on-body RF communication are presented, but no antennas specific for communication along the arm exist. To this aim, numerical simulations are performed using a cylindrically layered arm model to design a novel, electrically small, capacitively loaded, meandered, 2.45 GHz monopole antenna. The antenna is fabricated using 3D printed polylactic acid and validated both in a static human arm channel and in a dynamic setting, where the human subject performs various tasks. This antenna outperforms an off-the-shelf printed circuit board (PCB) antenna by 18 dB and a rectangular patch antenna by 4 dB in terms of link budget at a separation distance of 20 cm, both in line of sight and non-LOS path loss experiments. Additionally, while performing four commonplace activities, the average power received increased by 20 dB in an on-body link established between two of our novel antennas rather than two of the PCB antennas. These results will aid in the development of wireless prostheses used by a growing number of amputees.