Design on uniform aperture field distribution of slit array planar antenna consisting of copper-foil-coated dielectric substrate by taking account of slab modes at 60 GHz

A planar antenna fed by an over-sized hollow metal waveguide, whose top plane consists of slit array etched on a copper-coated dielectric substrate, has been proposed at 60GHz band. We tried to make a uniform aperture distribution on the slit array to improve the antenna efficiency. The gain was not however increased and the radiation pattern was degraded compared with that based on the Kirchhoff's scalar approximate theory. To overcome such difficulty, we investigated unwanted slab modes generating in the dielectric substrates and devised how to make a uniform aperture field distribution suppressing the unwanted slab modes.