Complex Modes in Parallel-plate Waveguide Structure Filled with Left-handed Material

The parallel-plate waveguide structure partially filled withLeft-handed material (LHM) is carefully investigated. It is shownthat complex mode is the constituent part of complete eigen mode set inthe structure independent of parameters of the configuration andoperating frequency; it means that purely propagating and purelyevanescent mode fields are not a complete set, unless complemented bythe complex mode fields. Numerical results are presented to illustratethe propagation characteristics of present parallel plate waveguide andthe role of complex mode fields in step discontinuity modeling. It isfound that convergence can not be achieved in the mode matchingprocedure unless the complex modes are included in field expansions.