Analysis Of Bandwidth Expansion And Application Of Leaky Coaxial Cable

Compared with ordinary transceiver antennas and RF coaxial cables,the leaky coaxial cable not only has the function of axial transmission,but also couples with the surrounding electromagnetic signals.It also has uniform electromagnetic radiation,low coupling loss,low electromagnetic pollution,and easy installation.This thesis is based on the “Research on Design Theory of Coupling Loss in Leaky Coaxial Cables” research project.It is designed to expand the bandwidth of the LCX and apply it to wireless communications in tunnels and other buildings in blind zone.For the upgrading of mobile communication systems,this thesis designs a leaky coaxial cable with a wider range of application frequencies based on actual needs.After briefly introducing the research status,structure,classification,radiation principle and main electrical parameters of leaky coaxial cable,select the LCX of 50-22 type as the design basis,and use the single eight-shaped slot as an example to design the leaky cable for frequency band expansion;The HFSS electromagnetic simulation software is used to determine the cycle P,length L and inclination angle ? of the cable outer conductor slot,and use the optimized single eight-shaped LCX to expand the use frequency band.When the LCX outer conductor is triple eight-shaped slot,the frequency band range will be expanded to 564.19MHz-3949.33MHz;By shifting the triple eight-shaped slots in the period of the outer conductor or add small round holes to effectively suppress the resonance point.Then the coupling loss and transmission attenuation of the LCX in the 900MHz-3300 MHz frequency band are analyzed,and the LCX which satisfies the wireless communication requirements is selected for the study of the radiation characteristics of tunnels and other closed-spaces.Based on the design of leaky coaxial cable,this thesis simulates the application of LCX wireless communication in practice.First of all,it explains the theory of field distribution calculation of the LCX in free space and tunnel environment,according to the relevant standards,the simulation model of the arched railway tunnel will be established.And the analysis of the field distribution at different locations was carried out to determine the laying position of the LCX in the middle of the tunnel.Subsequently,the transmission and radiation characteristics of the LCX in free space and in the tunnel environment are compared and analyzed.The method of field distribution analysis was used to study the communication of the buildings in blind zone.According to the simulation results,the LCX has a smaller coupling loss in the tunnel environment and can be well matched to the onboard antenna.When it is laid on top of a building corridor,the indoor electric fields on the left and right sides are evenly distributed.It can be determined that the LCX designed in this thesis can achieve good wireless communication in the closed-domain space.According to the mobile user's requirements for signal transmission speed and quality,leaky coaxial cables will be widely used as signal transmission lines in various weak field coverage areas.Therefore,the application of broadband LCX will be the trend of the times.This thesis' s design ideas and simulation methods have important reference value for the engineering application of leaky coaxial cable.