On the convergence of common FDTD feed models for antennas

Abstract

The finite-difference time-domain (FDTD) method is routinely used to calculate the input admittance/impedance of simple antennas. The value of the input admittance/impedance depends on the level of discretization used in the method, and should converge to a final value as the discretization becomes finer. In this paper, the level of discretization necessary for convergence is studied using two common feed models: the hard-source feed and the transmission-line feed. First, the simplest and most naive methods for introducing the voltage and the current in these models are considered, and the results for the admittance are shown not to converge. Next, improved methods for introducing the voltage and current in these models are constructed. The results for the admittance are then shown to converge, and guidelines are offered for the level of discretization needed for convergence. In addition, two general problems associated with the computation of the admittance are discussed: the agreement between admittances computed with different simple feed models, and the agreement between these admittances and measurements.

Assessment of the local SAR distortion by major anatomical structures in a cylindrical neck phantom

“…It is positioned at the 2.5 mm gap between the two conducting (σ = ∞) poles. The modelling of the antenna is carried out with space steps down to 0.5 mm which provides accurate results as presented by Hertel et al [18]. …”

Comparison of Three FDTD Modeling Techniques for Coaxial Feed

“…Fine discretization of the inner conductor. Finally, the inner conductor is modeled using the fine discretization of FDTD cells around the coaxial probe, earlier investigated in the context of its effect on calculation of input impedance of a monopole antenna [1]. In this technique, we implement a graded mesh for the region around the feed point in a precise manner to avoid unwanted reflections from the cell junctions.…”

“…This paper addresses the difficulties reported in numerical modeling of coaxial feed probes [1]. A range of finite-difference time-domain (FDTD) modeling techniques (e. g., gap, magnetic frill and transmission line modeling) was successfully applied for specific applications.…”

Stable coaxial waveguide‐port algorithm for the time‐domain finite‐element method

“…Further, a body-of-revolution formulation of the FDTD scheme applied to a monopole on a ground plane was used by Maloney, Smith, and Scott [9] to discretize (in detail) a part of the coaxial cable, which was truncated by a boundary condition for the dominant mode. Hertel and Smith [10] compared the most common FDTD feed models using convergence studies. The finite-element method (FEM) allows for local mesh refinement, which is appropriate for small features of feeding structures (see [11] for an account of the FEM).…”