Grating lobe suppression of narrow-wall slotted waveguide array antenna using thin narrow-wall waveguides in millimeter-wave band

Slotted waveguide array antenna is popular for use in millimeter-wave applications. The waveguide is assembled from two parts divided at the center of the broad-wall to reduce leakage from the gap. However, as the slot spacing is one guided wavelength and is larger than a wavelength in free space, grating lobes appear. It is possible to shorten the spacing between the radiation slots in the tube axis direction of the waveguide when the slots on two waveguides are triangularly arranged. But slot spacing is still large in the diagonal direction. We designed a slot array antenna on thin narrow-walls to suppress the grating lobes. The simulated characteristics are presented in this paper.