Antenna Concepts for Millimeter-Wave Automotive Radar Sensors

Automotive radars are on the market since 1999, both in the frequency range around 24 GHz as well as 76.5 GHz, with a new frequency band ranging from 77 to 81 GHz intended for medium and short-range sensors. The choice and design of the respective sensor antennas are determined by the requirement for high gain and low loss combined with small size and depth for vehicle integration, the challenges by the millimeter-wave frequency range, and a great cost pressure for this commercial application. Consequently, planar antennas are dominating in the lower frequency range, while lens and reflector antennas had been the first choice at 76.5 GHz, partly in folded configurations. With increasing requirements towards a much more detailed observation of the scenery in front or around the vehicle, multibeam antennas or scanning antennas have been designed, and solutions based on (digital) beamforming with a number of integrated antennas are in use or under development. General antenna concepts, partly including some system aspects, as well as three realized antenna configurations will be described in detail in this contribution.