Curved oversized EM waveguides: adiabatic modes and parabolicequation

摘要

Two alternative representations of the wave field in a curvedoversized electromagnetic waveguide are discussed: adiabatic modes,matched to the local value of the axis curvature, and full-wave solutionof the vectorial parabolic equation. The latter, although beingasymptotically equivalent to the adiabatic mode theory, displaysadditional diffraction effects. A simplified complex WKB analysis isperformed in order to estimate residual mode conversion in smoothwaveguide bends. Application of the vectorial PE to radio propagation intunnels is illustrated with numerical examples