Propagation of electromagnetic waves in a waveguide with a multi periodically nonuniform and nonstationary filling

Propagation of electromagnetic TE waves in a waveguide of arbitrary cross-section with a multiperiodically nonuniform and nonstationary filling is considered. Analytic expressions for TE field are obtained under the assumption of small modulation indices m1 and m2 of the filling. The frequency of the ''strong interaction'' between the signal wave and modulation wave is found