Antenna De-embedding in FDTD-Based Radio Propagation Prediction by Using Spherical Wave Function

Finite-difference time-domain (FDTD) method is one of the promising approaches for the propagation prediction. However, since the computational domain includes both the antennas and the propagation environment, their coupling prevents evaluating individual contributions to the channel response. As a result, the simulation becomes always specific to the given antenna type or orientation and cannot be reused for other configurations. The simulation also requires the internal structure of the antenna which is often unavailable and/or difficult to be modeled. These problems can be addressed by antenna de-embeddeding which separately models the antenna and the propagation environment, hence the purpose of this paper. In particular, this paper proposes the implementation of spherical-wave-function (SWF) channel modeling using the FDTD method. Instead of modeling the real antenna structures inside the computational domain, the single-mode spherical wave source and the observation points are utilized. The spherical wave source is achieved by a cubical dipole array. The spherical wave source is first validated, including the investigation of the effects of cell and array size. The narrowband channel response synthesized by the proposed approach is then validated numerically through comparison with the transmission formula in free space and the conventional antenna-embedded simulation in the human shadowing environment as well.