Waveguide and/or antenna assemblies for RADAR sensor assemblies/modules, particularly those for vehicles. In some embodiments, the assembly may comprise a waveguide block defining one or more waveguides, each waveguide defined by a waveguide groove. In some embodiments, at least a portion of at least one waveguide groove is non-straight, such as meandering/oscillating back and forth. An antenna structure may be operably coupled with the one or more waveguides, which structure may comprise an array of one or more slots. In some embodiments, a single, elongated slot of the one or more slots may extend along an axis of each waveguide groove for delivering electromagnetic radiation from a corresponding waveguide of the one or more waveguides therethrough.