Modeling of a cylindrical wire antenna with flat end caps using a rigorous moment method technique

With recent capabilities for accurately and efficiently modeling electrically thicker wire antennas, questions concerning the necessity of including end caps in the model have resurfaced. The finite charge on the ends, which can significantly affect the current distribution, as well as improve convergence and stability of the solution, has been characterized in the past by several approximate models. However, a more in-depth analysis of a wire antenna with end caps is necessary for completely characterizing the end charge density and understanding its effects on the near-field behavior and the current distribution of the wire. Such a treatment is especially important for moderately thick wires or resonant structures. A rigorous method of moments formulation is developed in this paper for the analysis of cylindrical wire antennas with flat end caps. Circumferentially invariant axially directed trigonometric current basis functions are assumed on the cylindrical surface, and pulse charge density basis functions are assumed on the end caps. In addition, the formulation introduces a ring charge at the outer boundary of the top and bottom end caps to account for the edge discontinuity. Exact analysis techniques are employed to obtain the solution to the electric field integral equation.