Electromagnetic Reflectometry with Coaxial Cable Models-Currents in Time Domain
Abstract: This application note describes how electromagnetic simulations using WIPL-D Pro, 3D EM simulation software, can be used together with WIPL-D Time Domain Solver (TDS) module to perform the time domain reflectometry simulation. TDS performs transient analysis of a 3D electromagnetic structure. The time-domain response of a structure is calculated using frequency domain simulation and Fourier transform. The tool is integrated into WIPL-D Pro software environment so that the frequency domain simulation and conversion to the time-domain are performed automatically.
Reflectometers can be used for non-destructive locating and characterization of discontinuities in coaxial cables. In real-life, for example, time domain reflectometry is applied for locating faults in airplane wiring. For precise locating of cable faults, so called spread spectrum time domain reflectometry is used.
In order to show the speed and accuracy of WIPL-D electromagnetic solver, three models of coaxial cables were simulated and generator currents calculated in time domain. The first model represents a straight coaxial cable with a fault. The dielectric between the cable conductors is air. For this structure, a theoretical result is available and could be used as a referent result to compare with the results obtained from WIPL-D simulations. The second model corresponds to a plain, curved cable. Finally, the third model represents a curved coaxial cable with a fault. For the curved cables, dielectric between the conductors has frequency dependent characteristics. All three coaxial cables have the same length.
The location of the cable fault as obtained with WIPL-D simulation and the one calculated based on EM theory are in excellent agreement.
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