W-band Antenna Array Based on Compact Feeding Network for Both Medium and Long Range Integrated Applications

It is difficult for conventional 77 GHz automotive radar antennas to cover the field of view for both medium-range radar and long-range radar simultaneously. The existing solution is to switch between two sets of antennas for medium-range and long-range radar, at the expense of a larger antenna footprint. Extra insertion loss will be introduced by the switch, which may influence the system signal-to-noise ratio. In this paper, a compact antenna array with a flat-shoulder shaped radiation pattern is presented, which enables simultaneous support for both medium-range and long-range radar application. In order to improve the design efficiency, a mixed optimization method, including non-linear fitting and aggressive space mapping, is utilized to synthesis this special flat-shoulder-shaped radiation pattern. In addition, a compact substrate-integrated waveguide feeding network is designed for realizing a compact array footprint while reducing parasitic radiation. The proposed antenna is fabricated using a low-cost single-layer printed circuit board process. Measurement results demonstrate a peak gain of 19.8 dBi and a desirable flat-shoulder-shaped radiation pattern at 77 GHz, making it a promising candidate for 77 GHz automotive radar applications.