A novel millimeter-wave slotted waveguide array antenna has been developed for automotive radar systems. An antenna structure suitable for mass-production is proposed in this paper. The waveguide is composed of two parts; an upper plate and a bottom plate. It is not necessary to contact closely them because they are divided at the center of the broad wall of the waveguide where the electric current is small. In addition, grating lobes are suppressed by using a cylindrical cavity around each slot and by controlling the slot arrangement without using dielectric material in the waveguide. We have fabricated the proposed antenna by metal injection molding. The measured antenna efficiency is 55 %, which is quite high in comparison with any other conventional low cost millimeter-wave antennas. This efficiency is almost the same as that of the antenna fabricated by precision metal machining. In this study, it is confirmed that the proposed antenna could be manufactured at a low cost.
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