Research And Implementation Of The Front-end System For Wireless Human Body Communication

Wireless human communication technology with the advantages of low power consumption,simple structure,high safety and easy integration.It can be widely used in the identification,confidential information transmission,healthcare and other fields.In hence,the human body used as a wireless transmission channel of human communication technology is studied in this paper.Communication signal coupling mode to the human body,human tissue modeling,the design and realization of transceiver based on waveguide coupling and antenna coupling are studied and discussed.Firstly,the electromagnetic properties of human tissues were studied.The cuboid and cylindrical five-layer tissue arm models were proposed.On this basis,two kinds of waveguide coupling transceivers with different dielectric layer structures were designed.The best communication band for the air dielectric layer transceiver is 713 MHz,and the maximum value of S21 is-16.44 d B.The best communication band for the FR-4 dielectric layer transceiver is 685 MHz,and S21 is-22.18 d B.In addition,the influence of the thickness of the transceiver dielectric layer,the distance between the two electrodes of transmitter,the distance between the transmitter and receiver,the distance between the transceiver and human body surface were studied,The feasibility of wireless body communication through the waveguide coupling was verified by the simulation analysis.Secondly,a single frequency microstrip antenna,a compact dual-band microstrip antenna,a planar leaf-shape monopole ultra wideband antenna with fractal feature and a planar circle-shape monopole ultra wideband antenna with fractal feature were designed for the human body communication,according to the band and safety requirements of human communication and compared with the traditional antennas.These antennas are used as the transceiver antennas to carry out the simulation analysis and physical test.The frequency band of the single-frequency microstrip antenna on arm model is 2.45 GHz,and the measured frequency is 2.46GHz;a compact dual band microstrip antenna with resonant frequencies of 1.9GHz and 2.45 GHz is designed by meander current method.The area of the antenna is only about 30% of the single frequency antenna.The resonant frequencies are 1.9 GHz and 2.4 GHz on the arm,and the measured frequencies are 1.9 GHz and 2.41GHz;the simulation bandwidth of the leaf-shape monopole antenna and the circle-shape monopole antenna both can cover the UWB band.The measured results show that the two antennas can meet the UWB antenna requirements.Moreover,the effects of the distance between the antenna and the arm,and the distance between the transmitting and receiving antennas on the insertion loss of the front-end system were analyzed.Finally,the front-end system of wireless human body communication was tested and analyzed.The measured frequency of the waveguide coupling human body communicaton is 693 MHz,and S21 is-25.6d B,which is close to the simulation result and meets the requirements of human body communication.The single-frequency microstrip antenna,the dual-frequency microstrip antenna,the leaf-shape monopole and the circle-shape monopole antenna can transmit wireless signal by human body within 40 mm,80mm,160 mm and 80 mm,respectively.The waveguide coupling and antenna coupling human communication front-end system were designed through theoretical research,simulation experiments and experimental verification.The best frequency for waveguide coupling human body communication was given and the maximum transmission distance of the four antenna coupling systems were given.The feasibility and effectiveness of wireless human communication front-end system are verified by experiments in this paper.