Design of narrow-wall slotted hollow waveguide array for arbitrarily linear polarization in the millimeter-wave band

In this paper, a high-gain and high-efficiency slotted waveguide planar antenna in the millimeter-wave band was developed. In the design of slotted waveguide arrays for arbitrarily linear polarization such as 45-degree inclined polarization for automotive radar systems, slot spacing is one guide wavelength which is larger than a wavelength in free space. Consequently, grating lobes appear in the radiation pattern. So, a slotted waveguide planar antenna composed of post-loaded narrow-wall slots and a single-layer power divider was developed. A planar antenna was fabricated to measure the performance. The measured gain is 33.2 dBi and antenna efficiency is 56% at 76 GHz. Grating lobe level is 28.6 dB lower than the main lobe level. Since the proposed structure remains simple, the antenna is expected to be manufactured by metal injection molding for a low cost