Modelling Arbitrary Complex Dielectric Properties -- an automated implementation for gprMax

TL;DR

This paper introduces an automated module for gprMax that enables accurate simulation of complex dispersive dielectric materials, expanding the software's capabilities to model arbitrary electromagnetic properties in GPR applications.

Contribution

Developed a new gprMax module that automatically models arbitrary dispersive dielectric materials using multi-Debye expansions, enhancing simulation accuracy for complex materials.

Findings

Module can simulate Havriliak-Negami, Cole-Cole, Cole-Davidson, Jonscher models

Supports arbitrary dispersive materials with user-defined permittivity

Improves GPR material modeling accuracy

Abstract

There is a need to accurately simulate materials with complex electromagnetic properties when modelling Ground Penetrating Radar (GPR), as many objects encountered with GPR contain water, e.g. soils, curing concrete, and water-filled pipes. One of widely-used open-source software that simulates electromagnetic wave propagation is gprMax. It uses Yee's algorithm to solve Maxwell's equations with the Finite-Difference Time-Domain (FDTD) method. A significant drawback of the FDTD method is the limited ability to model materials with dispersive properties, currently narrowed to specific set of relaxation mechanisms, namely multi-Debye, Drude and Lorentz media. Consequently, modelling any arbitrary complex material should be done by approximating it as a combination of these functions. This paper describes work carried out as part of the Google Summer of Code (GSoC) programme 2021 to develop a new module within gprMax that can be used to simulate complex dispersive materials using multi-Debye expansions in an automatic manner. The module is capable of modelling Havriliak-Negami, Cole-Cole, Cole-Davidson, Jonscher, Complex-Refractive Index Models, and indeed any arbitrary dispersive material with real and imaginary permittivity specified by the user.