Input Resistance Changes and Related Performances of a Normal-Mode Helical Antenna in a Human Body Application
Keywords:Human body, NMHA, phantom, RF
Recently, ingestible capsule endoscopy has been developed to ease the dosimetry process in the stomach and tract. In this application, a helical antenna is used because its shape is suitable for a capsule. The electric performance of a coil antenna can be analyzed by the normal-mode helical antenna (NMHA) concept. Previously, the design equations for NMHA have already been developed in free space application. Application of NMHA in the human body is innovative. Antenna design equations and electrical performance should be clarified. Presently, only self-resonant structure equations are clarified. In this paper, fundamental electric performances such as the input resistance, bandwidth and radiation characteristics are clarified through electromagnetic simulations and experiments. As for a human body tissue, the muscle is selected and a muscle phantom is used for measurements. It is made clear, that the input resistance and the bandwidth are increased by the increase of the human body conductivity, while the antenna gains are decreased.
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