  The dispersion properties of rectangular metallic waveguides periodically
loaded by uniaxial resonant scatterers are studied with help of an analytical
theory based on the local field approach, the dipole approximation and the
method of images. The cases of both magnetic and electric uniaxial scatterers
with both longitudinal and transverse orientations with respect to the
waveguide axis are considered. It is shown that in all considered cases
waveguides support propagating modes below cutoff of the hollow waveguide
within some frequency bands near the resonant frequency of the individual
scatterers. The modes are forward ones except the case of transversely oriented
magnetic scatterers when the mode turns out to be backward. The described
effects can be applied for the miniaturization of the guiding structures.
