Space-wave-type leaky mode carrying dominant-mode-like modal current distributions

A recently explored non-zero cut-off leaky mode is reported to coexist with the well-known bound mode in a suspended microstrip placed in a large U-shaped conducting container to suppress any surface wave leakage. This new space-wave-type leaky mode is confirmed by rigorous full-wave modal investigations and three-dimensional scattering analyses. The new leaky mode bears strikingly similar modal current distributions and near-strip transverse electric field patterns to the bound mode. Thus, the new type of leaky mode is an indispensable companion to the bound mode for a suspended microstrip.