Finite element method modeling of the wire thickness of a monopole on a circular ground plane

Abstract

Simulations and measurements of the input impedance and matching of a cylindrical monopole at the center of a circular ground plane are presented. The design parameters are the monopole length (0.231 to 0.261), the monopole radius (10 ⁻⁵ λ to 5 × 10 ⁻³ λ), and the ground plane radius (0.2λ to 2.0λ), where λ is the wavelength. Using new numerical results from the Finite Element Method (FEM), previous theoretical impedance results for an infinitesimally thin element are shown to be inaccurate for monopoles of practical thicknesses since there can be a strong dependence on the wire thickness—even for electrically very thin wires. The FEM offers convenient modeling for the wire thickness and the results match well with physical experiments. To obtain good antenna impedance matching to a 50 Ω impedance, that is, 5 11 < — 10 dB, for any ground plane radius greater than 1/2 (an arbitrary lower bound) and any practical wire monopole radius, the simulations show that a monopole length of 0.241 can be used.