Research On Multi Node Spectrum Hole Detection Technology Based On Time Reversal Technology

Time Reversal(TR)has attracted more and more attention in recent years due to its unique space-time focusing characteristics.With the wide application of Wireless Sensor Networks(WSN)in medical and aerospace fields,the WSN in the ISM band is faced with the increasingly serious problem of inter node crosstalk and the shortage of spectrum resources.In order to solve this problem,this paper uses the WSN as the research object in the complex multipath environment and in the range of ISM frequency band,and applies the space time focusing transmission mechanism of TR electromagnetic wave.From the angle of electromagnetic wave propagation,the key technology of new spectrum cavity detection based on time inversion of electromagnetic wave focusing transmission is developed.It focuses on the key technical problems of the spectrum resource constraints faced by the node distributed WSN in the complex multipath environment,as well as the serious crosstalk between the main users and the cognitive users under the super-resolution.Firstly,for hardware design,this paper designs and processes a super-resolution antenna based on the inverted F microstructural impedance line loading.At the central frequency of 2.45 GHz,the unit spacing of the super-resolution antenna is about lambda /41,the unit-10 dB bandwidth is 200 MHz,and the isolation between the units is lower than-15 dB.Based on this antenna,when designing the WSN communication system with super resolution,we can reasonably apply the antenna to user communication according to the system index.Secondly,for the electromagnetic simulation of spectrum cavity under TR,the WSN communication system model in complex multipath environment is built by using the designed patch antenna and semi closed metal cavity.Based on this model,with the increase of the number of TRM,the more concentrated distribution of electric field density in the field,the larger the area of the spectrum cavity area,and the quantitative analysis of the 16 TRM numbers,compared to the traditional communication mode TR communication method can improve the "white space" surface product in the field about 48.7%.The research of the spectrum hole detection scheme provides a theoretical guidance for future multi user access technology.Finally,in view of the feasibility verification of the simulation model,this paperis based on the experimental test of the electromagnetic simulation model established in the previous section,and demonstrates that the TR technology can effectively realize the spectrum empty area area of the dense deployed WSN system,and verify the feasibility of the multi node spectrum cavity detection technology based on the TR technology.Using the super resolution antenna,the experimental verification of the WSN node deployment scene under super-resolution is carried out,and the focusing experiment under different TRM numbers in the enclosed metal cavity is completed,which provides a highly referential design for the WSN node spectrum resource allocation technology under superresolution.