The theoretical interpretation of measurements of "wavefunctions" and
spectra in electromagnetic cavities excited by antennas is considered.
Assuming that the characteristic wavelength of the field inside the cavity
is much larger than the radius of the antenna, we describe antennas as
"point-like perturbations". This approach strongly simplifies the problem
reducing the whole information on the antenna to four effective constants.
In the framework of this approach we overcame the divergency of series of
the phenomenological scattering theory and justify assumptions lying at the
heart of "wavefunction measurements". This selfconsistent approach allowed
us to go beyond the one-pole approximation, in particular, to treat the
experiments with degenerated states. The central idea of the approach is to
introduce "renormalized" Green function, which contains the information on
boundary reflections and has no singularity inside the cavity. More information can be found here.