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This paper presents a novel implementation of forward modeling methods for simulating the reflectometry responses of faults in the shields of coaxial cable or other shielded lines. First, a cross-sectional modeling was used to determine the characteristic impedance of various wire sections. These values were then incorporated into longitudinal models to simulate the overall reflectometry response. The finite-difference method is a cross-sectional modeling method that was used to simulate cross-sectional characteristic impedance. Results obtained using this method are accurate within 1% of analytical solutions, and can be simulated very quickly using in-house codes. The finite-integral technique (FIT) is also used to model chafes on wires with TEM and higher order modes. Because FIT is computationally slow, a curve-fitting technique is used to predict the chafe profile within 0.01% of the simulated values. Modified transmission matrix and S-parameter methods are used to provide responses with accuracies within 0.3% of the measured profiles.
Date of Publication: April 2013