A pair of opposed metallic plates are disposed with a spacing therebetween to form a waveguide space without side plates. A plurality of power radiating slots are formed in one of the metallic plates. A lens antenna is provided for forming a flat equiphase wave plane at the power feed opening of the waveguide space, so that power is propagated in the waveguide space in the TE mode and radiated from the slots. PAT 15627-1
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