Wideband SIW Cavity-Backed Slot Array Antenna with Flat Gain Characteristics for 79 GHz Automotive Radar

A wideband millimeter-wave SIW cavity-backed slot array antenna is proposed for 79 GHz automotive radar applications. The antenna element is composed of a slot fed substrate integrated waveguide (SIW) cavity which operates in TE
₂₁₀
mode, 2 pairs of rotationally symmetrical L-shaped radiating slots and 2 matching metallic blind holes. An 8-way SIW parallel power divider together with the antenna element is then utilized to feed a 2 × 4 array. By arranging the positions of metallic blind holes and metallic via holes, the electromagnetic energy leaking from bonding layer can be suppressed so that it causes no disturbance on radiation pattern while the SIW structure remains unchanged. The measured results show that the array antenna has flat gain characteristics in the frequency band of 75-82 GHz with gain variation less than 1 dB. Simulation and measurement results agree very well.