Abstract
Local emitters of waves (or local actuators of dimensions much less than the wavelength of the wave to be controlled) present a necessary part of most of active control systems. This paper is devoted to some properties of emitters (local emitters at most) in the regime of maximum (resonance-like) absorption.
Such an emitter has an absorbing cross-section with dimensions about the wavelength of the wave to be absorbed. This property is referred to the waves of different physical nature, emitters of different constructions, different multipolarity, boundary problems of different geometrical dimension (n=2 and n=3).
Especially the local 3-dimensional antennas of simple multipole structure, could ensure the absorbing cross-section unbounded, growing at the increasing of multipolarity order, remaining physically local.
Regime of maximum absorption is formulated both in spectral and temporal representations in terms of so called generalized forces and velocities referred to some oscillatory degrees of freedom of boundary problem considered.
Some aspects of cooperative and individual strategy of absorbing emitters and problems of their stability and causality of control are considered. Examples when emitters could help or oppose each other are shown.