Abstract: Antenna assemblies for vehicles, such as RADAR sensor antenna assemblies. In some embodiments, the assembly may comprise a waveguide block defining an array of waveguide grooves and an array of antenna slots. Each antenna slot in the array of antenna slots may be at least partially aligned with a waveguide groove of the array of waveguide grooves of the waveguide block. The assembly may further comprise an absorptive layer comprising an array of openings corresponding with the array of antenna slots. The absorptive layer may be configured to dissipate surface currents on the waveguide block such as, for example, by way of the material used to form the absorptive layer and/or the thickness of the absorptive layer and/or to suppress fascia reflections.