New radar architectures employ multiple transmitters and receivers to enhance their performance, combining wide and narrow beams to improve the spatial resolution. In this contribution, two antenna system configurations based on stacked geodesic lenses are compared. These lenses are fully-metallic parallel plate waveguides that present very low transmission losses in the millimetre-wave band. Narrow beams are generated by a 15-port Luneburg-Rinehart lens with a scanning span of +/- 50 degrees and 23.4 dB gain at 77 GHz. For wide beams, two alternatives are proposed. One alternative is a 3-port defocused lens antenna with a scanning angle of +/- 50 degrees and 14.5 dBi gain. The second proposal is a 12-port Luneburg-Rinehart lens fed with 1-to-4 power dividers forming a 3-port antenna with a scanning span of +/- 45.5 degrees and 16.2 dBi gain.