An Ultrawideband Printed Monopole Antenna Analyzed with the Theory of Characteristic Modes

In this paper, the analysis of an UWB monopole antenna using the Theory of Characteristic Modes is presented. It starts from the modal study of an asymmetric dipole (structure 1), and then complements and compares it with a broadband monopole (structure 2), aiming to understand the operation principle of the proposed antenna. To achieve this, the electromagnetic properties of the structures are analyzed through the generation of its characteristic angles, modal radiation patterns, characteristic currents, and the power contribution percentage of each mode to the total radiated power, providing a vision on how the superposition of individual characteristic modes enables UWB operation. The prototype model is fabricated, and the measured results agree very well with the full-wave simulations results. The proposed prototype has a very low profile and operates in the frequency band from 2.8 GHz to exceed 10 GHz for a reflection coefficient S11 less than -10dB.