In-wafer helical antenna for automotive radars

A novel design for silicon (ε_r = 11.9) based dielectric-loaded square helical antenna completely embedded in the silicon wafer with a horn-shaped reflector is presented for 77GHz automotive radar. Most of the silicon around the helix is etched out using deep reactive ion etching to form a low-loss mechanical support and dielectric core of the antenna. Moreover, it also results in significant reduction in the high substrate losses. Simulation results show that the proposed antenna has high gain, wide bandwidth, circular polarization and narrow beamwidth. As compared to conventional axial-mode square helical antenna, it has 3dBi higher gain, 10dBi improvement in front-to-back ratio and better radiation efficiency.