Work-Energy Principle Based Characteristic Mode Theory for Yagi-Uda Array Antennas

TL;DR

This paper introduces a work-energy principle based characteristic mode theory tailored for Yagi-Uda array antennas, revealing fundamental differences from scattering objects and enabling effective modal analysis.

Contribution

It develops a generalized characteristic mode theory for Yagi-Uda antennas using the work-energy principle, which was not possible with conventional CMT.

Findings

Derived the work-energy principle for Yagi-Uda antennas.

Proposed a generalized characteristic mode theory based on WEP.

Provided a physical interpretation of modal significance for various Yagi-Uda antenna types.

Abstract

Work-energy principle (WEP) governing the work-energy transformation process of Yagi-Uda array antennas is derived. Driving power as the source to sustain a steady work-energy transformation is introduced. Employing WEP and driving power, the essential difference between the working mechanisms of scattering objects and Yagi-Uda array antennas is revealed. The difference exposes that the conventional characteristic mode theory (CMT) for scattering objects cannot be directly applied to Yagi-Uda array antennas. Under WEP framework, this paper proposes a generalized CMT for Yagi-Uda antennas. By orthogonalizing driving power operator (DPO), the WEP-based CMT can construct a set of energy-decoupled characteristic modes (CMs) for an objective Yagi-Uda antenna, and then can provide an effective modal analysis for the Yagi-Uda antenna. In addition, a uniform interpretation for the physical meaning of the characteristic values / modal significances (MSs) of metallic, material, and metal-material composite Yagi-Uda antennas is also obtained by employing the WEP-based modal decomposition and the field-current interaction expression of driving power.