| ABSTRACT: With the development of modern society, there is a higher and higher requirement of wireless communication. Traditional discrete antenna systems can hardly satisfy the requirement of wireless communication in complex environments. Meanwhile, leaky coaxial cables are widely used because of the advantages such as uniform coverage of signals, wide-frequency band for use, and designable radio wave channel for different environmental conditions. Nowadays, during the construction of subways all over the world, using LCXs is the first choice to achieve the field intensity coverage. So there is a common situation that many LCXs exist in the same space at a distance of only20or30centimeters. In this case, the designers and uses wanted to understand the laws of coupling characteristics between LCXs, and proposed relevant subjects. That is practical background of this paper. At the same time, how do the LCXs interact with each other? What are the factors that may affect the coupling characteristics between LCXs? And how to reduce the coupling to minimum? These problems have important academic significanceBased on paractical background and academic value, combined with project of National Science Fund for Distinguished Young Scholar, this paper has researched on the coupling characteristics between LCXs, built research models derived the coupling formula, and analyzed the coupling characteristics. This paper has also defined the formula of coupling value, analyzed the parameters that affect the coupling characteristics, and provided the ways to reduce the influence between LCXs.The main work and creative points of this paper can be summarized as follows:Firstly, the research has built the model to study on the coupling characteristics of LCXs with a continuous longitudinal slot, and proposed using the voltage ratio to express the coupling relationship between LCXs. And then, according to the analysis of the radiation field of slot aperture, the formula of coupling term between LCXs has been derived. At last, based on the formula, this paper has calculated and analyzed the influence of the variation of frequency, length of LCXs, and the distant between LCXs on the coupling characteristics.Secondly, based on the theory of coupling between LCXs with axially slot, this paper has built the model to study on the coupling characteristics of vertical slotted LCXs. Relevant formulas have been derived, and the coupling characteristics have been analyzed. And then, according to the actual circumstance, the coupling relationship has been studied under the situation that there is an obstacle between the LCXs. The formula of coupling relationship can be derived by using the high-frequency-ray method. And the coupling relationship has been calculated and analyzed from the aspects of obstacle’s size and location.Thirdly, based on the equivalent magnetic current, through analyzing the radiation field of magnetic current element, we can conclude the electric field distribution of slot aperture of LCX as a transmitter, and then the expression of coupling coefficient of the slot aperture can be deduced. Then the formula of coupling coefficient of the slot aperture of LCX as a receiver can be deduced through analysis. At last, the value of coupling coefficient of the slot aperture can be obtained through simulation. Combine with previous analysis of coupling characteristics, the coupling value can be determined at last. |
