Bloch Wave Analysis of Long Leaky Coaxial Cables

Leaky coaxial cables can be used as distributed radiators for indoor communications. When the number of slots is large, as it is often the case, the application of a full-wave analysis method is very demanding in terms of both memory and CPU time. In this paper an analysis technique, based on Bloch wave theory is presented. Slots are viewed as discontinuities in an open waveguide and a suitable basis of orthogonal polynomials is introduced to represent the modal amplitudes pertaining to the continuous spectrum. The radiation properties of the cable are discussed in detail in terms of the excited Bloch waves. Finally, the reflection coefficient at the junction between a uniform and a slotted cable is computed. The results are presented in the form of a chart, for general slot size and spacing.