Lower boundedness, global minimality, and uniqueness are established for the
solutions of a physically-motivated class of inverse electromagnetic-radiation
problems in (meta)material backgrounds. The radiating source is reconstructed
by minimizing its $L^{2}$-norm subject to a prescribed radiated field and a
vanishing reactive power. The minimization of the $L^{2}$-norm constitutes a
useful criterion for the minimization of the physical resources of the source.
The reactive power is the power cycling through the inductive and capacitive
parts of the source and its vanishing corresponds to the maximization of the
power transmitted in the far-field.