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A comparison of finite-difference, finite-integration, and integral-equation methods in the time-domain for modelling ground penetrating radar antennas

Development of accurate models of GPR antennas is being driven by research into more accurate simulation of amplitude and phase information, improved antenna designs, and better-performing forward simulations for inversion procedures. Models of a simple dipole antenna, as well as more complex models similar to a GSSI 1.5GHz antenna and a MALA Geo-science 1.2GHz antenna were investigated in free space and over lossless and lossy dielectric half-spaces. We present comparisons of simulated data using the Finite-Integration Technique, the Finite-Difference Time-Domain method, and a Time-Domain Integral Equation approach, as well as measured data. For each scenario, phase, amplitude, and the shape of the waveform were compared. Generally we found very good agreement between the different simulation techniques, and good agreement between experimental and simulated data. Differences that were evident highlight the significance of understanding how features such as antenna feeding and material dispersion are modelled. This degree of match between experimental and simulated data cannot be attained by using just an infinitesimal dipole model in a simulation - a model including the structure of the antenna is required. This is important for the many GPR applications which operate in the near-field of the antenna, where the interaction between the antenna, the ground, and targets is important.