Leaky modes at backward endfire on periodic printed structures

In this work, the transition at backward endfire between bound (nonleaky) and leaky modes on one-dimensional periodic structures printed on a grounded dielectric substrate is examined. This mode evolution has been characterized for a class of structures with a finite-width cross section. Such structures support leakage into surface waves as well as into space due to the presence of the substrate. The solutions in this transition region are calculated using an accurate full-wave moment-method approach that allows for the determination of both physical and nonphysical solutions, both of which play an important role in the transition region.