Planar antenna

A planar antenna comprising:

• a dielectric substrate;
• a feed line provided on a first surface of the dielectric substrate and having a first lateral side extending along a first direction and a second lateral side opposed to the first lateral side;
• three or more radiation elements arrayed on the first surface along the first direction and provided at the first lateral side and the second lateral side so as to alternately protrude;
• and
• an electromagnetic band gap structure having an arrangement region on the first surface, wherein
• the first surface includes a first adjacent region adjacent to the first lateral side and a second adjacent region adjacent to the second lateral side,
• the arrangement region includes a first arrangement region included in the first adjacent region and a second arrangement region included in the second adjacent region,
• the first arrangement region is defined by a perimeter of the electromagnetic band gap structure in the first adjacent region,
• the second arrangement region is defined by a perimeter of the electromagnetic band gap structure in the second adjacent region,
• the three or more radiation elements include a plurality of first radiation elements protruding from the first lateral side toward the first adjacent region, and one or a plurality of second radiation elements protruding from the second lateral side toward the second adjacent region,
• at least a part of the first arrangement region is positioned closer to the feed line with respect to a first imaginary line below, and
• at least a part of the second arrangement region is positioned closer to the feed line with respect to a second imaginary line below,
• the first imaginary line:
• a straight line parallel to the first direction and passing through the first adjacent region, an interval between the straight line and an imaginary center line below being twice w1 below,
• the second imaginary line:
• a straight line parallel to the first direction and passing through the second adjacent region, an interval between the straight line and the imaginary center line being twice w2 below,
• the imaginary center line:
• a straight line parallel to the first direction and passing through a center, in a second direction orthogonal to the first direction, of the feed line,
• the w1:
• an interval between the imaginary center line and a leading edge of the plurality of first radiation elements, and
• the w2:
• an interval between the imaginary center line and a leading edge of the one or the plurality of second radiation elements.