79-GHz SIW slot-coupled patch antenna array with low cross polarization and wide beamwidth

A 79-GHz wide-beam patch antenna and 1×8 antenna array with low cross-polarization levels are presented for automotive radar applications. A substrate-integrated-waveguide slot-coupled scheme was employed to reduce the cross-polarization level of the patch antenna. Two parasitic elements were added to the main patch to form a three-element subarray for beamwidth enhancement. The simulated E-plane half-power beamwidth (HPBW) of the patch antenna is 148°, and the cross-polarization level is 32.5 dB less than the co-polarization level at the boresight direction. For further gain enhancement, a 1×8 patch array was designed and fabricated. The measured results show that the proposed design can offer a wide HPBW of 144° and a low cross-polarization level of 28.3 dB less than the co-polarization level at 79 GHz.