The main idea of this work is to exploit this property for the first time and to realize wide-band and multi-band leaky wave lens antennas. In particular we will concentrate on the design of directive feeds for sub-mm wave applications. The key reason that renders the present leaky wave slot very suited for sub-mm sensing is that most of the THz sensors already use lenses. In most instances integrated receiver are located in the lower focus of a rotational symmetric elliptical dielectric lens antenna. These lenses are typically chosen because they do not suffer from loss of power in guided modes and moreover, since they are shaped elliptically with the eccentricity properly related to the dielectric constant, they also providing high-direct...