Impedance Characteristics and Field Separation of Body Implanted Antennas

In this paper, the input impedance characteristics variance and field region separation of the implanted antenna for body area communications are investigated. The input impedance of half-wave dipole wire antenna inside the human body torso and vacuum are calculated through HFSS simulation and theoretical formula. Moreover, impedance measurement results of previously proposed implanted antenna are shown in this paper. Compared with the free space/vacuum operating environment, biological tissue will dramatically shrink the input impedance and resonance frequency of the implanted antenna. On the other hand, far-field separation characteristics inside biological tissue are investigated for three kinds of implanted antennas which are dielectric resonance antenna (DRA), helical antenna and discone antenna. The relationship between the receiving antenna aperture and far-field boundary are simulated. In words, this paper gives insights on the impedance variance and far-field separation of the implanted antennas, which will provide reference for implanted antenna development, body area communication system design as well as antenna measurement and corresponding on-body antenna design.