Frequency versus time domain simulation of nonuniform TDR system

Time domain reflectometry (TDR) is finding increased applications for civil engineering field instrumentation. New applications are being identified based on innovative design of TDR sensor system. Numerical simulation plays an important role for guiding and evaluation of these new designs. This paper discusses the implementation of numerical simulation of frequency domain and time domain models of nonuniform TDR system. The frequency domain model is based on the concept of impedance transform, which can easily incorporate the dispersive characteristics of construction materials. The time domain simulation is carried out by FDTD method. Results of simulation based on both frequency domain model and time domain FDTD method are compared to identify the relative merits of these numerical methods. The simulation of TDR system responses establish the basis for aiding TDR sensor system design and is incorporated into the inversion procedures to be investigated in the future.