Microwave Propagation in Anisotropic Waveguides

A detailed analysis of the propagation of electromagnetic waves in circular waveguides whose walls are anisotropic is carried out. The physical property of the wall is described in terms of ¿anisotropic surface impedance¿ and this has two principal components, which, in general, do not run along the co-ordinates of the cylinder. It is shown that, whatever the orientation of the principal axes of the surfaces, all E- and H0-modes are stable. Formulae are derived for the propagation coefficients and attenuation coefficient of the waves, and these are expressed in terms of the impedance components of the surface. Furthermore, it is shown that all higher-order H-modes are unstable in such waveguides unless the principal axes of the surface coincide with the co-ordinate axes of the surface: a wave that is stable in an anisotropic waveguide, whatever the orientation of the axes, is a ¿spinning H-wave.¿