A radar sensor for motor vehicles, having a transmitting antenna in the form of a planar group antenna having multiple antenna elements situated side by side on a shared planar substrate, and having a feed network and a switching device for supplying microwave power to the antenna elements. The antenna elements are situated at equal distances in at least one row; the feed network is designed for supplying the antenna elements with the microwave power having a phase shift which increases at constant increments from one end of the row to the other; and the switching device is designed for controlling the supply of the microwave power to the antenna elements in such a way that, depending on the operating mode, the supply is implemented in a mirror-inverted fashion from opposite ends of the at least one row.