Electric Field Distributions of NMHA Inside and Outside of a Human Body Phantom

Abstract

In order to establish a communication link between a sensor inside of a human body to a receiver outside of the human body, electric field distribution performances of the antenna inside of the human body need to be clarified. A Normal Mode Helical Antenna (NMHA) is proposed as the antenna used for this research for the purpose of using it as the antenna for Wireless Capsule Endoscopy (WCE). In this paper, the performances of NMHA which are self-resonant structures, input resistance (Rin) and efficiency (n) are presented. The antenna is designed at frequency of 402 MHz. The designed NMHA is placed inside of human body phantom with permittivity (εr) of 11.6 F/m that represents fat layer. The conductivity (σ) of the phantom is from 0 to 1 S/m. The electric field distributions of NMHA inside the phantom are observed in details at σ equals to 0, 0.3 and 1 S/m. From the electric field distributions, propagation loss of signal (Lz) from NMHA across the human body phantom can be estimated. Calculation of electric field degradation is also presented in this paper. A half-wavelength dipole antenna is then added to the NMHA model to act as receiver to check NMHA's signal strength. The result is presented as S21.