PERFORMANCE OF AN IMPLANTED ELECTRICALLY COUPLED LOOP ANTENNA INSIDE HUMAN BODY

Abstract

Implanted antennas are widely used in hyperthermia and biomedical applications. The antenna needs to be extremely small while maintaining a permissible Speciflc Absorption Rate (SAR) and being able to cope with the detuning efiects due to the dielectric properties of human body tissues. Most of the proposed antennas for implanted applications are electric fleld antennas such as Planner Inverted-F Antennas (PIFA) and micro-strip patch antennas. By minimizing the size of an electric fleld antenna, the near zone electric fleld will increase, resulting in higher SAR. This work is devoted to design a miniaturized magnetic fleld antenna to overcome the above limitations. The proposed electrically coupled loop antenna (ECLA) has high magnetic fleld and low electric fleld in the near zone and therefore, has a small SAR and is less sensitive to detuning efiects. ECLA is designed at the Medical Implanted Communication Service (MICS) band with dimensions of (5£5£3mm 3 ). ECLA has been simulated inside one-layer human body model, three-layer spherical human head model, human head and human body. From the simulation results, ECLA inside the human body has a 5MHz{3dB bandwidth, i14dB gain, and radiation e-ciency of 0.525%. The 1g average SAR inside the human body for 10mW input power is about 1W/kg which is 7times lower than the SAR for a patch antenna of the same size with the same accepted power.