Research On Radiation Properties Of Leaky Coaxial Cables

The applications of leaky coaxial cables (LCXs) have been extended to a variety of communication systems under complicated environments because of the ability of providing uniform wireless coverage at confined areas. In this thesis, the radiation characteristics of kinds of LCXs are studied by hybrid methods combining commercial electromagnetic simulation software and far-field integration approach or curve-fitting. The main work and innovation parts in this thesis are concluded as following:1. The effect of the structural parameters and the operating frequency on the polarization property of LCXs with overlapped triangle or horizontal triangle slots is investigated. The results show that it’s possible to design LCXs which can radiate a circularly polarized wave within a45°angular region around the cable by properly choosing the structural parameters of overlapped triangle or horizontal triangle slots. Using these novel LCXs, the detrimental fading caused by orientation effects in public mobile communications can be effectively mitigated.2. The radiation characteristics of three sorts of LCXs with combined rectangular, bidirectional horizontal triangle and graded rectangular slots are analyzed to solve the following three issues.(1). The angular region around the cable in which the LCXs can radiate a circularly polarized wave is relatively narrow.(2). The fluctuation of coupling loss along LCXs is relatively large.(3). The system loss of LCXs with uniform slots increases with the length of LCXs. Meanwhile, three types of LCXs are designed by choosing proper slot structural parameters. These three types of LCXs are able to effectively solve or reduce the above three problems.3. The electric field distribution in rectangular slots on LCX is studied. An empirical formula for calculating the maximum value of the electric field distribution in rectangular slots is derived by curve-fitting all the data obtained from numerical method. The formula is applicable to the standard1-5/8" LCX and is generally in good accuracy. By applying the formula, the electric field distribution in rectangular slots on the LCX can be approximately expressed, which is very valuable for the investigation on the radiation characteristics of the LCX and for the LCX design.