Improved electric field modelling for TDR

Integral equation (IE) methods may be used to model the interaction between microwave signals and porous materials and hence lead to improvements in time-domain reflectometry (TDR) or other techniques for measurement of moisture content. Although they may employ pulse basis functions to represent the field in each cell of the discretized region, the inherent approximations limit accuracy. Higher order basis functions provide one alternative, but here we describe a method that retains the geometric and cell density advantages of delta functions, and improves accuracy by correcting for the field integration errors of the conventional moment method. Our approach circumvents errors that arise when assuming that the field of a cell is adequately represented by a source at its centre, and results in close agreement between empirical results and the model.