Magneto-electric dipole antenna array for 77 GHz automotive radar

A 1 × 4 magneto-electric dipole (ME dipole) antenna array for 77 GHz automotive radar is proposed. The ME dipole is fed by a fork-shaped microstrip line coupling through a dog-bone slot. To meet the requirements aimed at automotive radar applications, the beamwidths of the proposed antenna are well-designed. Specially, a method of adding passive elements on both sides of the array is proposed to increase the 3 dB beamwidth from ±34° to ±52° in azimuth. Additionally, in elevation, a 3 dB beamwidth of ±10° is achieved by designing the spacing between array elements. Moreover, based on low-loss printed circuit board substrates, radiation efficiency of the proposed array can reach approximately 90% at 77 GHz. Furthermore, a 4 × 4 array is established by arranging four 1 × 4 subarrays spacing 1.95 mm (half a free-space wavelength at 77 GHz) to study the interactions between subarrays for multiple input multiple output scenarios. A 1 × 4 and a 4 × 4 antenna prototypes are fabricated and measured to validate the correctness of this design. The results show that the proposed antenna is an eligible candidate for the medium- and short-range automotive radars.