a device with a substrate lens antenna uses a lens shaped dielectric body located on top of a planar feed antenna . a leaky wave antenna structure is used as feed antenna . the leaky wave antenna structure has a feed input and a first and second wave propagation branch extending from the feed input . the lens shaped dielectric body has a plane surface containing a focal point of the lens shaped dielectric body , the plane surface located adjacent the first plane , with the focal point adjacent the position of the feed input . preferably the lens shaped dielectric body is spaced from the leaky wave structure at a sufficient distance to remove most of the propagation speed reduction effect of the dielectric on wave propagation along the leaky wave antenna . this helps to suppress undesirable side - lobes .