Long-range antenna systems for in-body biotelemetry: Design methodology and characterization approach

Abstract

Long-range in-body biomedical telemetry enables monitoring of physiological parameters while maintaining mobility and freedom of movement. This emerging technology creates new applications in medicine, clinical research, wellness, and defense. Current in-body biotelemetry devices operate within about a meter around a user that limits their applicability. Here we examine the variety of approaches that, combined, can significantly extend the operating range. The radiation efficiency is constrained by attenuation and reflection losses in tissues. First, choosing an optimal operating frequency can minimize the losses. A specific antenna design is then required to decouple the antenna from a body. Two successful antenna design approaches are reviewed: (1) using loop antennas and (2) dielectrically loaded microstrip antennas. On-body matching layers and repeaters can be used to further improve power transmission. Finally, we present the radiation characterization method for in-body antennas in spherical phantoms with a direct illumination technique using an analog fiber optic link.