Leaky cables are a very efficient solution to solve the problem of radiopropagation where on-board receivers are momentarily in a radioelectric shadow area, like in tunnels, in urban environment or in hilly countries. This paper presents and describes the properties of some specific architectures which can solve most of the problems encountered. These analyses are based on practical realisations in various European countries. Some described solutions make possible to meet some specific requirements like maintaining the communication even in the case of a leaky cable breakdown. An important part of this paper is also devoted to present a theoretical model for predicting the value of the leaky cable coupling loss which is an important parameter to determine system efficiency. Coupling is indeed a key element for the choice of the most appropriate cable and system architecture. It has been evaluated for both coupled mode cables and radiated mode cables. Some comparisons between the theoretical model and measurements made on site are also proposed. Good agreement has been observed in most cases.
Abstract