Low-Sidelobe Series-Fed Microstrip Antenna Array for 77 GHz Automotive Radar Applications

A low-sidelobe series-fed microstrip linear array antenna and a planar array antenna operating at 76-77 GHz are designed. The linear array antenna consists of 12 microstrip patch elements and a quarter of wavelength impedance transformer. By using the differential evolution algorithm (DEA), the widths of patch elements and the inter-element spacing are optimized, which results in a low sidelobe level in the E plane. Prototypes of the two antennas are fabricated and measured respectively. The measured gain of the linear array antenna is 16.1 dBi and the sidelobe level (SLL) is -20.5 dB in E plane with half power beam width (HPBW) of 8.4° at 77 GHz. The measured gain of the planar array antenna is 22.8 dBi and the SLL is -15.5 dB in E plane and -17.1 dB in H plane at 77 GHz.