Equivalent Circuit With Frequency-Independent Lumped Elements for Coated Wire Antennas

A 7-element lumped-parameter equivalent circuit is derived for wire antennas coated with a thin dielectric and/or magnetic material. The derivation is based on a method for transforming any coating to an equivalent magnetic coating on a wire with a different radius. The derived circuit is composed of a five-element sub-circuit for bare wire antennas plus a two-element parallel circuit for modeling magnetic coatings. Compared to full-wave simulations and measurements, this equivalent circuit provides reasonably accurate results over a broad frequency range that includes the first resonance. It can be used to estimate the input impedance of a coated antenna without requiring an EM solver. It can also be used to model coated antennas in circuit simulations.