Design Of The Wearable Antennas Based On Compact EBG Structures

In recent years,wearable antennas based on Electromagnetic band-gap(EBG)structures have been drawing attention in the applications of wireless body area networks(WBAN).Because of in-phase reflection characteristic,loading EBG structures on the back of antennas helps increasing antenna gain and decreasing radiation damage towards human body.The specific design contents are listed as follows:(1)A dual-band monopole with an EBG structure formed with dual-band ringshaped resonator is proposed.The antenna works simultaneously in 2.4~2.4835 GHz and 5.15~5.825 GHz band used in wireless local area networks(WLAN).Firstly,the equivalent circuit model of the EBG unit cells explains the mechanism of miniaturization.Secondly,the distribution of reflection phase shows the principle of dual-band EBG structure and the distribution of surface current illustrates the principle of dual-band monopole,respectively.Finally,simulated and measured results verify the practicability and safety to human body.(2)A monopole with a unique logo of Lanzhou University based on a ring-shaped EBG structure with interdigital capacitances are proposed.It works in 2.20~2.50 GHz,and its size miniaturization is realized by the interdigital capacitances.The comparison of phase distribution and equivalent circuit model is used to analyze miniaturization principle,and simulated results as well as measured results verify the stability of the antenna when it is bended and works near a human.(3)A microstrip monopole antenna with an improved uniplanar compact electromagnetic band-gap(UC-EBG)structure that works in 2.25~2.51 GHz is presented.The capability of suppressing cross-polarization is verified by the comparison between the reflection phase of co-polarization and cross-polarization,and the equivalent circuit model helps to reveal the differences between conventional UCEBG and improved UC-EBG.Simulated and measured results show the stability and safety of the antenna,which means the antenna is suitable for the practical applications.(4)A planar inverted-F antenna(PIFA)with an inverted-C ring-shaped EBG structure that works in 2.30~2.65 GHz is presented.The extraordinary feature is to utilize conductive textile instead of copper,which makes it more capable of conformal.The number of unit cells are increased in order to decline the radiation harm to human body,which makes it meet the requirement.