Research On The Coupling Loss Of Leaky Coaxial Cable In The Blind Zone

Leaky coaxial cable has many advantages such as homogeneously wide coverage, low coupling loss, easily assembled and changed communication circuits, fewer pollution, and so on. When it's difficult to communicate in wireless communication or the external propagation condition is in very bad situation, the leaky coaxial cable can still work well. Leaky coaxial cable is widely used in confined areas such as subways, tunnels, underground markets, mines, and other buildings in blind or semi-blind zones, so it has broad applied prospect.At first, this paper briefly introduced the development and basic knowledge of leaky coaxial cable, and then explained the physical configuration, category and several related important electric parameters of leaky coaxial cable. According to the structure of leaky coaxial cable, I explored its radiation principle and analyzed its radiation model. By using cylinder Fourier transform, I obtained the free space radiation fields of leaky coaxial cable with different slots on the outer conductor. After that, this paper analyzed the measure methods and calculating method of the coupling loss detailed, which was the most important electric parameter of leaky coaxial cable, discussed influence factors of coupling loss and the relationship between coupling loss and radiation loss, put forward methods which could be used to improve the theory value of coupling loss. At last the paper analyzed the coupling loss in blind zone, combined with geometrical optics and waveguide matching method deduced the expressions of the coupling loss of leaky coaxial cable, which have vertical and sloping slots on the outer conductor, including rectangular tunnel, circular tunnel and well shielded space indoor, and discussed the external factors that would act on the coupling loss in the tunnel.