Leakage effects of dominant and higher order modes on slotline

The properties of the slotline when the dominant bound or leaky wave propagates, together with the behaviour of new higher order modes are investigated. The frequency range in which the slotline transmits the bound wave only is determined and the closed-form formula for its upper cut-off frequency is presented. The evolution of the propagation constant in the spectral gap between the propagating bound and leaky wave regions is shown. The influence of the substrate losses on leaky wave behaviour is presented. Some new aspects of both space and surface higher order leaky waves on the wide-slot line are discussed.