Grating-lobe suppression by placing a parasitic-dipole layer in alternating-phase feed slotted waveguide arrays

摘要

Grating lobes are radiated in oblique directions when slots are spaced by a guided wavelength in alternating-phase feed slotted waveguide arrays. This paper proposes installation of a parasitic-dipole layer over the slot array to suppress the grating lobes. Including periodicity of the element arrangement, an analysis model is introduced by using a rectangular waveguide with periodic boundary conditions in the two sets of the sidewalls in the external region. A amplitude ratio of the higher modes over the dominant modes in the periodic-wall waveguide is calculated to evaluate the grating lobe level. The level is suppressed below -17dB for polarization parallel to the waveguide axis.