  A substantial control of dispersion features of the hybrid EH01 and HE11
modes of a circular waveguide which is completely filled by a longitudinally
magnetized composite finely-stratified ferrite-semiconductor structure is
discussed. A relation between the resonant conditions of such a composite
gyroelectromagnetic filling of the circular waveguide and dispersion features
of the supported modes are studied. Three distinct frequency bands with the
single-mode operation under normal as well as anomalous dispersion conditions
of the EH01 mode are identified by solving an optimization problem with respect
to the filling factors of the composite medium. The possibility of achieving
isolated propagation of the HE11 mode is revealed.
