Research On Microwave Detection Of Brain Activity Based On Reconfigurable Antenna Array Technology

Since the 20th century,the field of human brain science has gradually set off a wide range of attention in the world,microwave technology with its unique advantages,more and more widely used in the field of life science.Non-invasive brain activity detection has been one of the main research directions in the field of brain science in the past decade,and the classification of the state of brain activity and diagnostic imaging have been the focus of research.Using microwave technology to detect the functions of different regions of the brain could help to gain a better understanding of how the human brain works.In this paper,related research on the use of microwave technology for brain activity detection has been done.The process of detecting the brain using electromagnetic wave technology is described in detail from the perspective of the characteristics of the electrical parameters of the excitable zone media caused by the brain nerve activity and the state of electromagnetic waves propagating in three layers of dynamic media.When the nerve is excited,the potential on both sides of the cell membrane changes,which in turn affects the electrical parameter characteristics of the area.Relying on this change,the use of electromagnetic waves to obtain synchronous changes in brain activity and transmission phase,and then analyze the function of different brain regions.Subsequently,an antenna unit for brain activity detection was designed.At the same time,with the help of a high-precision three-dimensional head model,the scattered signals received in different directions of the antenna array are processed.The results show the effectiveness of brain activity detection using microwave technology.Finally,the research of the reconfigurable antenna array technique applied to microwave detection of brain activity was carried out.After the design and processing of antenna unit and RF front-end circuit,the design feasibility scheme carries on the bionic experiment of brain activity,and further verifies the correctness of the theory.The main contents and results of the paper are as follows:1.From the perspective of the neuroactivity in various states of the brain,the physiological environment of the brain,the physiological environment of the brain,the bioelectrical signal caused by the reciprocating movement of charged ions when nerve cells are active,which affects the change of the electrical parameters of the medium,and the transmission process of microwaves in the dispersive medium are described.According to the working principle of the brain nerve excitatory state,a hierarchical time-varying medium transfer model based on uniform plane waves is established.At the same time,the mathematical relationship between the transmission phase of electromagnetic waves and the characteristics of the dynamic when the medium becomes electrical parameters is constructed.In the dynamic time-varying medium,the process of causing the synchronous change of transmission electromagnetic wave phase in the dynamic time-varying medium is further described,and the characteristic variation frequencies of the two are equal.It provides the corresponding theoretical basis for the follow-up study.2.In view of the biological structure of human head and the specific requirements of microwave detection,the antenna unit structure is designed for microwave detection of brain activity.Firstly,a planar monopole omnidirectional antenna for brain activity detection research was designed,this structure takes advantage of the wideband characteristics of the planar hexagonal monopole antenna,miniaturized antenna by etching defective structures.In order to enhance the directional radiation capability of the antenna,at the same time,a petal-shaped resonance-based reflector is used,and it can produce in-phase reflection band in a wider frequency band.Moreover,the profile height is only0.1?₀.The measured impedance bandwidth of the antenna is 0.91 GHz-2.42 GHz?91%?,and the front-to-rear ratio in the frequency band is greater than 5 d B.The peak-to-peak ratio at 1.05 GHz reached 15 d B.The consistency of the test results and simulation indicates that the antenna has the characteristics of ultra-wideband,and it shows that this structure can be applied to the field of brain activity detection.3.Use electromagnetic simulation software to verify the rationality of the theory.Add a precise three-dimensional human head model,and set corresponding electrical parameters for different brain tissues.Build models in electromagnetic simulation software,according to the characteristics of the time-varying electrical parameters of brain functional area media,the neural activities of visual cortex and olfactory cortex are imitated at the corresponding positions.Building a 6-element antenna array on the outermost layer of the head model,the analysis of the specific absorption rate proves the safety of the antenna detection system.Using the time-frequency domain transformation method to record the scattered electromagnetic waves received in different directions,the influence of the change of the dielectric parameters?dielectric constant and conductivity?on the phase change of the transmission coefficient is thoroughly studied.The results prove the effectiveness of using microwave technology to detect neural activity in brain functional areas.Ultimately,analyzed the dispersion characteristics of different biological tissues in the head,and choose a suitable operating frequency between resolution and transmission depth.4.Experiments related to brain activity are carried out in the bionic brain model by using the reconfigurable antenna array technology.The microwave feed network design is based on Peregrine Semiconductor's PE42442A-Z RF switch chip and can be used for transceiver switching.After processing and measuring the electric circuit,the insertion loss of each RF channel is less than 3 d B,and the isolation between each branch is greater than20 d B.Afterwards,the antenna unit,radio frequency switch circuit and human head bionic model were used to form a 6-unit transceiver reconfigurable loop antenna array,which was used in the later experimental research of brain activity microwave detection.After in-depth study,the characteristics of the electrical parameters of different inorganic chemicals dissolved in water are analyzed,and the change rules are mastered to make a bionic model of brain tissue according to a certain ratio.In the end,After the bionic simulation experiment,analysis of brain activity information on different microwave transmission paths shows that the change of the dielectric parameters of the functional area will cause the change of the transmission phase.The measured change law is the same as the simulation data,which proves that the S-parameter phase change of the scattered waves in different directions can carry the information of neural activity in the brain excitation area.