A. Yu. Grinev, V. S. Temchenko

Complex point source beams are exact directionalwave fields obtained by an analytical extension of a Green-s function into complex space. To show that such accurate representations do indeed exist, we shall explain how to generate one and two complex point dipole (electric, electric and magnetic) model for T- horn that is used in precision near-field measurements or calibration procedures. Transmit T-horn antenna dipole modeling basis of calibration procedures reciprocity theorem set an integral relation on basis of transfer function between excitation voltage at the input and at the output of antenna at mediums and objects sounding which are located outside antenna and further registration of reflected field. In the approach under consideration, the real GPR antenna is substituted by an electric dipole located in a virtual point into complex space whose coordinates are determined experimentally. I.e. the vector transfer function (VTF) of the real antenna (e.g. T-horn) is replaced by a horizontal component of VTF of an electric dipole. Determining of coordinates of the virtual complex source of the transmitting antenna was carried out by registering scattered electromagnetic field in time domain from the "infinite" metal screen located in the far zone of the antenna. Both frequency response and virtual source coordinates are taken into account, which are determined by calibration procedures. Dipole antenna modeling parameters are determined on basis of linear inverse problem solution including the number of complex dipole moments, their coordinates and spatial orientation. Objective function determined as Euclidean norm between elements of parametric spatial and real data spatial and functions minimizing provide the choice of optimal values for such modeling parameters The determination of unknown parameters is realized by objective function minimization on basis of global optimization algorithms. The error of this model is within the measurement error of the T-horn pattern.