Patent ID: 7642981

Claim:
A slot antenna apparatus comprising: a grounding conductor, having an outer edge including a first portion facing a radiation direction, and a second portion other than the first portion; a one-end-open slot formed in the grounding conductor along the radiation direction such that an open end is provided at a center of the first portion of the outer edge of the grounding conductor; and a feed line including a strip conductor close to the grounding conductor and intersecting with the slot at least a part thereof to feed a radio frequency signal to the slot, wherein the feed line is branched at a first point near the slot into a group of branch lines including at least two branch lines, and at least two branch lines among the group of branch lines are connected to each other at a second point near the slot and different from the first point, thereby forming at least one loop wiring line on the feed line, wherein a maximum value of respective loop lengths of the at least one loop wiring line is set to a length less than one effective wavelength at an upper limit frequency of an operating band of the slot antenna apparatus, wherein branch lengths of all those branch lines among the group of branch lines, each branch line terminated at an open end and not forming a loop wiring line, are less than one-quarter effective wavelength at the upper limit frequency of the operating band, and wherein the grounding conductor is formed to include at least one section at the second portion of the outer edge, the at least one section gradually approaches an axis passing through the slot and parallel to the radiation direction with increasing distance from the first portion of the outer edge.