Qualitative characteristics of open waveguide resonator spectra

Analysis of elements (inhomogeneities) of the SHF channels is due to the solution of complex problems of mathematical physics. The paper deals with the results characterizing qualitatively the spectrum of open waveguide resonators. The features of analytical prolongation of diffraction problem resolvents into range of complex values of a frequency parameter have been studied as well as their distribution on the corresponding Riemann surface. The ranges in which the points of a spectrum can be involved are localized roughly, and the theorem of their existance has been proved. A basis for a numerical analysis of spectra and studying of resonance excitation processes both in the stationary (diffraction) and non-stationary regimes has been got