An antenna unit includes a dielectric substrate; a dielectric cover on the dielectric substrate; and an antenna array. The antenna array includes antenna elements arranged in the dielectric substrate and configured to form traveling waves propagating in the dielectric substrate and the dielectric cover. The antenna unit also includes at least one spatial matching element arranged in space formed inside the dielectric substrate, spatially matched with the dielectric cover, and coupled with the at least one antenna element. The spatial matching element is configured to be spatially matched with the antenna array with the dielectric cover and to reduce reflections of traveling waves propagating from the antenna array to the dielectric cover. The antenna device may be diversified.