Local-Field to Global-Field Transformation for Metamaterial-Inspired Antennas (Metantennas)

In energy transport theorem (ETT)-based decoupling mode theory (DMT), the diagonalizing input power operator (IPO) method was used to calculate the energy-decoupled modes (DMs) of antennas. Taking metamaterial-inspired antenna (metantenna) as a typical example, this paper proposes a method for modifying the original IPO, and also provides a DMs-based application—local-field to global-field transformation. Compared with the original IPO, the modified IPO has a more satisfactory numerical performance. The DMs-based local-field to global-field transformation method uses the DMs-based modal expansion to realize the determination for the global field from the field value on a local sampling surface. The sampling surface can either closed or open; when the sampling surface is closed, it can either enclose the metantenna or not. In fact, the DMs-based local-field to global-field transformation method can be viewed as a generalization for the conventional multipoles-based far-field to near-field transformation method.