Waveguide $3\times 2$ -Slot Subarray Antenna for Millimeter-Wave Car Radar

We design a $3\times 2$ -slot sub array antenna for millimeter-wave car radars in the 76 GHz band. A cavity is introduced and designed to reduce phase differences among the slots. We change the slot length, width, and spacing to improve the gain. The antenna is designed for a wide bandwidth to have double resonance by two reflection-suppressing walls in the feeding part. The measured antenna has a reflection below -10 dB across 76.4 GHz-82.0 GHz. The gain is 15.5 dBi and the sidelobe level is -15.5 dB at 78.5 GHz in the measurement.