Polarimetric responses of underground targets using an hybrid transfer function FDTD method

Polarimetry has become a very powerful tool to enhance the performance of all sort of radar detection systems. However, to the knowledge of the authors, it has found little or no interest up to now for a very special variety of radar systems: ground penetrating radars (GPR). The reason for this is the range at which the target is located. Due to the highly lossy media into which the wave propagates, the transmitting and receiving antennas are generally located close to the ground interface, for a maximum power transfer and a better signal reception. Objects at shallow depths cannot be considered to be in the far field. At the base of radar polarimetry is the scattering matrix which, unfortunately, is defined by the ratios of the scattered to the incident far fields components. Other results, have shown that the near field can be obtained easily using a standard FDTD computer code with some modifications. This paper goes a step further by explaining how to compute the far field scattering matrix and the polarimetric responses. The contribution of the interface to the polarimetric responses is also discussed.