Efficiency measurements of additive manufactured electrically small antennas

Additive manufactured prototypes based on a novel inverted-F antenna design are presented and measured results discussed. Radiation efficiency is computed with the aid of a Wheeler cap box; the resulting ratio of the antenna's quality factor to the lower limit described by Chu is shown to be 1.9 for a spherical variant. Measured and simulated S-parameter results show good agreement, with some evident discrepancies - these are explained by potential unknown changes to the powdered materials during the printing processes, and the rough surface finish of the metallization on the antennas.