Conformal Ingestible Capsule Antenna: A Novel Chandelier Meandered Design

Abstract

This paper investigates a conformal antenna for the ingestible bio-telemetric capsule system. This system has the potential to provide real-time biological information from within the human body via a radio frequency link. The balanced planar meandered dipole (concept used for antenna miniaturization through space-filling) is discussed along with the offset planar meandered dipole, which facilitates better matching. The conformal chandelier meandered dipole antenna (CCMDA), which is an extension of the offset planar meandered dipole and envelopes the capsule surface, is then investigated. The return loss, input impedance, and radiation pattern characteristics of the CCMDA are discussed in detail at the operating frequency of 1.4 GHz. Additionally, electrical components (specifically the batteries) are modeled inside the capsule to investigate their effects on the conformal antenna performance in free space. The capsule antenna is then inserted into a simple box model (a simplification of the human torso) and a 4-mm precision human-body model (Ansoft) where the detuning effects are observed and discussed. Finally, a circularly polarized receiver antenna design consisting of orthogonal dipoles is suggested which provides polarization diversity and is miniaturized to fit into a personal digital assistant (PDA) for portability of the data telemetric link.