Design of Automotive Radar Antenna for Covering Middle- and Long-Range With Dual-Circular Polarization

This article proposes an antenna based on the substrate-integrated waveguide (SIW) to cover both middle- and long-range with dual-circular polarization for automotive polarimetric radar at 78 GHz. The proposed antenna comprises six columns of SIW linear inclined slot arrays fed by two same feeding networks from both sides to realize right-hand circular polarization (RHCP) and left-hand circular polarization (LHCP). In addition, the established unequal phase and amplitude distributions of the feeding network result in a flat-shoulder beam. This type of beam prepares the required coverage range for both long- and middle-range radar using a single antenna. There is a fair agreement between the measured and simulated results, in which the proposed antenna’s gain is around 21.4 dBi and the axial ratio (AR) is lower than 3 dB throughout the operating frequency bandwidth. Besides, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$S_{11}$ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$S_{22}$ </tex-math></inline-formula> are less than −10 dB between 76.3 and 79.2 GHz, and isolation is around −35 dB.