Modeling and simulation of broad-band antennas using the time-domain finite element method

Abstract

This paper presents a time-domain finite element method (TDFEM) for the modeling and simulation of complex broad-band antennas. Two critical components, namely the modeling of antenna feeds and the truncation of infinite free space, are discussed in detail. An accurate waveguide port boundary condition is employed to model the commonly used coaxial feeds, which is also applicable to other waveguide feeding structures. An improvement to the simplified probe feed model is also presented. The formulation and implementation of perfectly matched layers are briefly described for the truncation of the TDFEM computational domain. Numerical examples are presented to demonstrate the modeling and simulation of typical broad-band antennas, which include a logarithmic spiral antenna, a Vivaldi antenna, and a Vlasov antenna.Index Terms-Broad-band antenna simulation, feed modeling, perfectly matched layers, time-domain finite-element method (TDFEM), waveguide port boundary condition.

Modal Resistance of Spiral Antenna

“…It is discussed here since a simplified gap-fed excitation across g can provide an accurate prediction of radiation patterns (when compared to measured results), but discrepancies are often encountered when using this feed to predict the input resistance. This has historically been attributed to the presence of a feed cable and mutual coupling [19], which often shifts the measured impedance of the test antennas below the theoretically predicted impedance.…”

“…Hence, a theoretical self-complementary impedance can be obtained by numerical simulation (for example, in [19]) but difficulties are faced in measuring this same value-the experimental observations in [18,20] illustrate this shift. This suggests that the modeling of the feed structure must be included in the calculation in order to verify with the measured results for impedance [20], or careful consideration must be taken to minimize the capacitive loading it can create.…”

“…The effective dielectric constant ε reff and the characteristic impedance Z 0 for the quasi-TEM propagating mode in PCPW can then be derived in (10) and 11, respectively.…”

“…These have been investigated experimentally and computationally since their initial development in the late 1950s [1,2], and a number of numerical methods have been developed and utilized in the decades following their introduction to model these broadband attributes. Examples of this include the method of moments based on a thin-wire assumption [3,4], finite-volume time-domain (FVTD) [5], finite-difference time-domain (FDTD) [6,7], finite element method (FEM) [8,9], time-domain finite-element method (TDFEM) [10], and similarly constructed commercial full-wave solvers [11][12][13][14].…”