“…Planar transmission lines with open boundaries have been widely studied to describe their radiation leakage properties [ Oliner , 2000]. In the past literature, the Spectral Domain Approach (SD) [ Oliner , 1987; Tsuji et al , 1991; Bagby et al , 1993; Di Nallo et al , 1998; Villegas et al , 1999, 2003] has been used to analyze this type of structures. The SD Approach was needed to express the Green's functions in such open structures and analyze the behavior of the constituent leaky‐wave modes.…”