Research On Multi-Mode Wearable Antenna In Wireless Body Area Network

With the development of science and technology,more and more wearable devices enter people’s lives.As a short distance communication network composed of wearable devices and implantable devices,wireless body area network（WBAN）,which is centered on human body,has become a hot research topic.Wearable antenna is the key device of wireless communication system,and its performance determines the quality of communication link.WBAN has three communication scenarios,and they require different radiation patterns for wearable antennas.Multi-mode wearable antennas can enrich the use scenarios of the device,improve the integration of the device and expand its functions,which is of great significance to the development of WBAN.The design of wearable antenna should consider the human safety and comfort.To ensure the former,the input power of antenna must be strictly required.To ensure the latter,the size and material of the antenna should be considered.On this basis,how to achieve multi-mode radiation is a huge challenge for researchers.In response to these problems,the thesis relied on the project commissioned by Liaoning Putian Digital Co.,Ltd.to conduct research on multi-mode wearable antennas.The main results obtained are as follows:（1）A tri-band wearable on-body repeater antenna is proposed.The antenna is designed by combining the plane inverted F antenna（PIFA）and patch antenna.The function of signal repeating between the implantable equipment and the external equipment is realized.In addition,another port excited the orthogonal mode on the same patch,which producing a new band.The antenna is measured on pork,and the measured gain is 1.16 dBi and 1.26 dBi at 2.38 GHz and2.45 GHz,respectively.When the input power of the antenna is lower than 22.3 dBm,the specific absorption rate（SAR）of each band can reach the standard,which meets the application requirements of WBAN.（2）A flexible dual-mode dual-polarized wearable antenna is proposed.Two modes of the antenna are excited on the basic circular patch.The frequency tuning and circular polarization radiation of the antenna are realized by utilizing eight slots,which lead to the dual-band dual-mode dual-polarized characteristics.Considering the comfort of human body,felt is used as the substrate for fabricating and measuring.The results show that the performance of the antenna is stable when it is worn.The measured gain of 2.45/5.8 GHz is 5.35 dBi and 5.76 dBi,respectively.Then the SAR and bending characteristics are verified by simulation.The antenna has the advantages of simple structure,easy processing and good human comfort,which has a good prospect in WBAN.（3）A miniaturized dual-mode dual-polarized wearable antenna is proposed.The antenna consists of circular and annular patches.TM₀₁ and TM₁₁ mode are excited simultaneously by the introduction of short pin.The directional circularly polarized radiation is realized by introducing two annulus slots.The antenna is fabricated of rigid substrate and felt,which realizes impedance matching,radiation characteristics and human comfort.The measured gain of 2.45/5.8 GHz is 1.9 dBi and 5.0 dBi,respectively.The antenna has good radiation characteristics and is suitable for WBAN.（4）A multi-mode multi-band reconfigurable wearable antenna is proposed.The antenna is designed by combining dual-band PIFA and dual-mode patch antenna.The reconfigurable feeding network realizes the switching from in-body mode to on-/off-body mode,which makes the antenna cover all communication scenarios in WBAN.The combination of PIFA mode and patch mode of the bottom antenna realize the dual-band operation.The tuning of the two modes resonance frequency of the top antenna are realized by loading the short pin in the center of the circular patch.The tri-mode antenna is measured on the body tissue,and the good impedance and radiation characteristics are verified.The measured gain of 2.45/5.8 GHz is 0.23 dBi and-2.36 dBi,respectively.When the input power is lower than 23.4 dBm,the SAR of each mode can meet the requirements.The antenna has a compact structure,multi-band and comprehensive modes,lead to a great application value in WBAN.