TIME-DOMAIN TECHNIQUE FOR CHARACTERIZING LEAKY COAXIAL CABLES.

Because of the inability of free radio propagation to provide ratio coverage for underground and certain above ground mobile communications, the leaky feeder technique has been of growing interest. For a successful underground communication leaky feeders provide guided and also leaky electromagnetic waves so that the field can be picked up by mobile receivers at distances away from and along the leaky line. It is the objective of this paper to present a time-domain technique suitable for describing the performance of leaky feeders. The proposed technique employs the equations derived from a signal flow graph procedure where the leaky cable is represented as three-port network with the third port being introduced to represent the leakage. It is shown that by sampling only segments of the transient response of the cable to an impulse waveform, the scattering parameters describing the performance of the cable can be obtained. The measurement procedure is described while experimental results for three different leaky coaxial cables are presented and compared with spot check frequency domain measurements. The text of this paper is in digest form.