Latex based near-endfire wearable antenna backed by AMC surface

Abstract

A near-endfire, artificial magnetic conductor (AMC) backed wearable antenna is proposed in this paper for wireless body area networks operating in the 2.4 GHz ISM band. The bidirectional-endfire radiation pattern of Yagi-Uda latex antenna is changed to off-axis near-endfire radiation using an AMC reflector also printed on latex. The antenna is separated from upper AMC surface using flexible Styrofoam of thickness 0.044λo at 2.4 GHz for best compromise between keeping the antenna structure low-profile and achieving an off-axis beam tilt radiation of ~74° towards end-fire direction. 0° reflection phase AMC surface is proposed to reduce downward radiations and consequently improve the antenna tolerance to positioning on the human body, and reduce the specific absorption rate (SAR) level for 2.4 GHz frequency band gap. Antenna performance in terms of return loss, radiation efficiency, extent of frequency detuning, gain and SAR level are studied for free space as well as CST MWS tissue-equivalent voxel model for proposed antenna design. The Yagi-Uda antenna backed with AMC reflector demonstrates the measured return loss bandwidth of 40 MHz (2.43-2.47 GHz) and gain of -0.2 dBi in endfire direction with improved on-body radiation efficiency of 74.82 % and reduced peak SAR level of 1.24 W/kg for 10 g tissue for the compact overall flexible latex antenna volume of 0.4λo × 0.4λo × 0.076λo at 2.4 GHz.