Composite Patch Array Antenna with built-in Polarizer for Reducing Road Clutter Noises of 76 GHz Automotive Radars

A composite patch array antenna with built-in polarizer has been newly proposed and developed to reduce road clutter noise of 76 GHz automotive radars by 20 dB, where a polarizer is placed in front of Tx and Rx patch arrays within their reactive near-field region to suppress cross-polarized sidelobe radiation from feeding lines of the patch arrays while maintaining a low-profile characteristic with 4 mm thickness. Additional metal-lined absorbers within the composite antenna structure, while terminating cross-polarized waves undesirably excited by the patch arrays, also serve as miniature clutter plates to further reduce sidelobes toward road surface. The resultant composite antenna has achieved sidelobe levels of -45 dB, with a 20 dB improvement from standard patch arrays, at elevation angles toward 90deg.