Analysis of leaky coaxial cables using mode-matching and fourier transform

Abstract

A leaky coaxial cable (LCX) is one of the important RF devices, which is widely used in various communication fields such as tunnel or railway communication, guided transportation systems, intruder detection, and mobile communication in large buildings, etc. In general, LCX plays two roles at the same time: One is a wave-guiding cable, which should be capable of transmitting wave through its entire length without too much attenuation, and the other is an antenna, which must be able to radiate or leak electromagnetic energy into the vicinity of cable maintaining stable signal level and low coupling loss. According to the aspect of radiation, LCXs are classified into two major groups; a coupled-mode LCX and a radiating-mode LCX. A radiating-mode LCX can radiate EM wave out of the cable, but a coupled-mode one leaks the energy into its vicinity. Therefore, with the radiating-mode cable, we can enlarge the coverage providing sufficient signal level to receivers. To obtain better physical insight into LCXs and to provide more accurate and efficient cable design methods, we have widely investigated the prominent characteristics of LCXs. In chapter 2, the electrostatic problem of an axial slotted coaxial cable is considered. Through our analysis, the electrostatic potential distribution and the capacitance of this LCX are examined. In chapter 3, a wave propagation of the LCX with infi-nite axial slot is studied. Through solving the eigenvalue problem of the wavenumber matrix, we can derive accurate propagation constants of a monofilar- and a bifilar mode. In chapters 4 and 5, we scrutinize various characteristics of widely used radiating-mode LCXs. LCXs with the periodic slots are considered in chapter 4. We can derive accurate three dimensional full-wave solutions both inside and outside of the cables. Especially, we can successfully deal with LCXs with finite number of slots on their outer conductor, which is impossible for the existing other methods. Furthermore,...