Leaky Coaxial Cable Electrical Characteristics Of Indicators

Leaky coaxial cable is called LCX. Because of the advantages of coverage uniformity, low price, simple structure and so on, leaky coaxial cable has been used widely in complex environment, such as coal mine, subway and train tunnels. Following the development of the mobile communication, the industry of LCX has made a great progress,. Nowadays, in order to adapt to wireless communication, the main topic is to research an ultra wide band LCX with new slots that covers many frequency bands.In this thesis, beginning with the basic theory of LCX, the paper introduces the basic physical structure, the slots'type which existed on the outer and some important electrical performance indicators-operation frequency-band, transmission loss and coupling loss. According to the interaction in different ways of the electromagnetic energy with internal and external environment, LCX is classified as two kinds. Then, according to the slots on the outer conductor, the radiation theory is discussed; the paper analyzes the condition for innovation of radiation and the bandwidth when LCX is working on single-mode radiation pattern. In addition, the paper pointes out the way to expand the bandwidth and briefly introduces the resonant performance in the operation frequency-band of LCX.The paper emphasizes on two performance indexes-transmission loss and coupling loss. This thesis describes separately the composition of transmission loss-conductor loss, dielectric loss and radiation loss. Because U-slot of LCX has been used widely in train tunnels, buildings and so on, the paper studies and discusses the factors that affect the transmission loss in simulated progress with U-slot of LCX. In order to obtain the coupling loss of LCX, by the method of near-field to far-field based on Huygens, the field distribution surrounding LCX obtained with CST simulation based on FDTD is used Matlab programming software to receive the far-field distribution.Finally, two types of LCX with new slots are designed. The paper gives an elementary study on transmission loss of the news. By CST software, we simulate the length, width and spacing of the new slots. The transmission loss S21 obtained from CST software have good agreement with the U-slot of LCX. This will illustrate that the new design of LCX is consistent with leakage indicators.