Study of local quasi-TEM waves in oversized waveguides with one hard wall for killing higher order global modes

An oversized rectangular waveguide with one hard wall was previously demonstrated to be suitable for feeding a planar slot array because it has higher-order-mode-killing properties, i.e. it supports propagation of a single quasi-TEM parallel-plate-type mode, and no higher order modes. In the present paper we detect instead many local quasi-TEM waves that follow the hard surface with identical propagation constants. The local quasi-TEM waves can be excited to produce a combined mode that is the single quasi-TEM parallel-plate-type mode. We propose to characterize this interesting feed guide in terms of the performance of the local quasi-TEM waves.