Entire-Structure-Oriented Work-Energy Theorem (ES-WET)-Based Characteristic Mode Theory for Material Scattering Objects

Entire-structure-oriented work-energy theorem (WET) framework is used to establish the characteristic mode theory (CMT) for material scatterers. Diagonalizing driving power operator (DPO) method is proposed to calculate characteristic modes (CMs). Solution domain compression (SDC) scheme is introduced to suppress spurious modes. An electromagnetic energy characteristic equation similar to the energy eigen-equation in quantum mechanics is derived for unifying the modal analysis theories of classical electrodynamics and quantum mechanics. Using the concept of driving power in the WET framework, the physical meaning of characteristic values is revealed; the reason leading to the nonorthogonal characteristic far fields of lossy scatterers is provided; it is explained why the conventional CMT fails to analyze some classical transmitting antennas; the physical interpretation for normalizing modal real power to 1 is given; the Parseval’s identity in CMT is derived; the classical concept of quality factor (
$Q$
-factor) is generalized to a novel concept of field-current phase-mismatching factor (
$\Theta $
-factor). Using the diagonalizing DPO method with the SDC scheme, the spurious modes outputted from the conventional diagonalizing impedance matrix operator method are suppressed. Both the novel SDC and conventional dependent variable elimination schemes confirm the same conclusion that the spurious modes originate from overlooking the dependence relationships among the currents in CM-generating operator.