Waveguide and/or antenna structures for use in RADAR sensor assemblies and the like. In some embodiments, an antenna module may comprise a waveguide and an antenna structure, such as one or more slots/slits operably coupled with the waveguide groove. The antenna structure may be positioned and configured to deliver electromagnetic radiation from the waveguide therethrough. A plurality of tapering surfaces may be formed along the antenna structure. Each of the plurality of tapering surfaces may be formed so as to alternate between opposing sides of the antenna structure and be spaced apart from each adjacent tapering surface of the plurality of tapering surfaces.