Finite-Element Analysis and Modeling of Antennas

In this chapter, we described the finite-element analysis of complex antenna problems. First, we described the formulations of the FEM in both the frequency and time domains using vector basis functions, which are also known as edge elements. We then discussed two important issues for the FEM simulation of antennas. One was the mesh truncation and the approaches covered included absorbing boundary conditions, perfectly matched layers, boundary integral equations, and the FDTD interface. The other issue was the modeling of antenna feeds and the extraction of antenna parameters such as the input impedance and radiation patterns. The antenna feed models discussed included the current probe, the gap generator, and the waveguide feed such as coaxial lines. This was followed by the description of numerical schemes for modeling infinite periodic phased arrays as well as finite arrays in both the frequency and time domains. In addition, practical guidelines were provided for the choice of solution technology based on either frequency- or time-domain methodologies. Numerical application examples were presented to demonstrate the FEM analysis of a variety of antennas. These included narrowband antennas such as microstrip patch and monopole antennas, broadband antennas such as a ridged horn, a spiral, a sinuous, and an inverted conical spiral antenna, and both infinite and finite periodic array antennas. Finally, we briefly addressed the FEM modeling of antenna-platform interaction. The application examples clearly demonstrated that the FEM is a powerful numerical simulation tool for the analysis and design of highly complicated antennas, and that it holds great potential for future antenna developments.