Design Of Wearable Antenna System For Body Area Network

In recent years,with the development of wireless body area network communication,wearable antennas,which are the most important part of body area network communication,have received extensive attention in the fields of military,medical,sports and so on.And its radiation performance directly determines the quality of body area network communication.Among them,on-body communication requires the antenna to have the characteristics of omnidirectional radiation,while off-body communication requires antenna to have radiation characteristics that are perpendicular to the human surface pattern without obvious attenuation.Therefore,the designed wearable antenna is preferably capable of achieving both types of radiation at the same time.At the same time,the wearable antennas are generally integrated into clothing and wearable devices,so the antenna needs to have the characteristics of low profile,miniaturization,and conformality with the human body.In general,there are two types of wearable antennas,one is a miniaturized stereo antenna designed with a hard substrate,and the other is an antenna designed with a flexible textile material that can be deformed by human motion.Due to its special use scenario,wearable antenna needs to consider the influence of human electromagnetic environment on the antenna in the design process.Similarly,the impact of antenna radiation on human health should also be taken into account.This paper firstly introduces the research significance of wearable antennas and the research status at home and abroad,then determines the research content of this paper.The second chapter is the introduction related theories.In the third chapter,a two-element wearable antenna system with pattern diversity is designed.One of the antenna elements is a planar inverted F antenna,which has the characteristics of directional pattern perpendicular to the human body surface without obvious attenuation and can be used to receive electromagnetic waves scattered by walls,ground and furniture.The other is a top-loaded monopole,which has the characteristics of horizontal omnidirectional pattern parallel to the human body surface and can be used to receive signals crawling along the human body surface.Both antenna elements can cover 5.8 GHz ISM band.Since the distance between the antenna elements is very small(about 0.048?@5.8GHz),there will be some coupling generation.In this paper,the decoupling between antenna elements is achieved by adopting the method of slotting on the public ground to maintain the antenna size.In the fourth chapter,a wearable pattern reconfigurable antenna array is designed.The radiating part of the antenna is obtained by four planar inverted F antennas rotating 90 degrees in the counterclockwise direction,and the down layer is a feed network made by three equal power splitters.When four units are excited by four equal-amplitude and same-phase signal sources,the omnidirectional radiation pattern parallel to the human body surface is realized.When the output has the same amplitude,but the phase of ports 1,4 and 2 and 3 is 180 degrees,directional radiation perpendicular to the surface of the human body can be realized.So this antenna can meet the communication requirements of wearable devices in different environments.Finally,this paper summarizes the previous research and gives a prospect for future research directions.