A Linear Array of Transverse Slots on a Hollow Waveguide with a Layer of Parasitic Dipole-Quartets for Sidelobe Suppression

A linear array of transverse slots on the broad-wall of a hollow waveguide suffers the grating lobe problem because the element spacing is longer than the free-space wavelength. In order to solve this problem, a parasitic dipole quartet is introduced for each slot instead of the dipole pair. This is confirmed experimentally. A 6-element array using this configuration with reflection-canceling posts is designed by the method of moments. The grating lobes are suppressed below -15 dB in the array, which is confirmed by measurements.