On-body Antennas For Wireless Body Area Network Applications

With the popular applications of wearable devices,Wireless Body Area Network(WBAN)which is a kind of body-centric communications improves the quality of our life in entertainment,health and medical field.Due to the large relative permittivity and loss media,the body tissue has a significant impact on the impedance mathicng and radiation performance of antennas.It's a challenge to design on-body antennas with a miniature dimension and low Specific Absorption Rate(SAR).Different application senarios require various on-body antennas with distinct radiation patterns.And it's of great importance to study the technics of miniaturization,wideband,high gain and high efficiency of on-body antennas.In this paper,we propose several novel on-body antennas,which all can obtain a good performance in vicinity of body tissue.The major work can be summarized as three parts:1.A miniaturized dual-band dual-mode button antenna is presented.This work support on-and off-body communications at two frequencies simultaneously and independently.At lower band,the antenna based on the fundamental mode of PIFA realized an omnidirectional pattern,which provide a reliable coverage of body.At upper band,the higher order mode of PIFA cooperates with reflection of ground results in a broadsight directional radiation pattern.The button antennas utilizing the accessory of clothes can be integrated directly with textiles,but avoids bending and crumpling effects of textile antennas.And we evaluate the SAR performance and the maximum input power of the button antenna.In addition,the transmission performance between two proposed antennas mounted on the body is investigated by measuring the transmission loss.As for the on-and off-body transmissions,the statistic evaluation is done not only in different locations but also in different senarios.Besides,we propose another dual operating mode button antenna on flexible ground structures for wearable communications.2.A wideband slot antenna array using AMC with conical pattern for VR application is introduced.We employ slot antenna elemnt to realize wideband performance,and obtain an omnidirectional conical pattern with an array with 2×2 elements.Without reducing the bandwidth,AMC metasurface decreases the absorption of body tissue and increase the gain and radiation efficiency of the antenna array.Integrating the wideband slot antenna array in the 3D printed VR model,we consider the practical application environment including a standard head phantom.The experimental results verify that the proposed design has a good performance even oprating in the pratical application environment.3.Circularly polarized slot antennas for off-body communication are investigated.We design a wideband circularly polarized slot antenna with a tradiational power divider and a 90° phase shifter.In order to improve the performance of the proposed design,we proposed another circularly polarized filtering slot antenna.The feeding network of the filtering slot antenna integrates resonator structures,which results in a bandpass filtering response of the broadsight gain.Due to the isolation and protection of AMC metasurface,this two slot antennas still obtain circularly polarization radiation when working on human body.