An antenna system comprising: an antenna array comprising: a ground a dielectric substrate of a rectangular shape; a plurality of rectangular radiation patches arranged at intervals in the length direction of the dielectric substrate and formed on the top surface of the dielectric substrate; a plurality of coupling patches arranged in correspondence to the plurality of radiation patches, each of which formed on the top surface of the dielectric substrate and extending from a side of the dielectric substrate to a position spaced from a corresponding radiation patch by a distance; and a metal support arranged on the lower surface of the dielectric substrate and extending from an edge of the lower surface of the dielectric substrate downward to the ground, a layer of air having a predetermined thickness being formed between the dielectric substrate and the ground, and a waveguide horn array comprising: a rectangular metal plate having a cross section comprised of a plurality of rectangular holes arranged in the length direction of the rectangular metal plate, the lower part of each hole being formed as a rectangular waveguide, and the upper part of each hole being formed as a horn, and two grooves extending in the direction along which the plurality of holes are arranged and having a predetermined depth, one being formed at a side of the holes on the top surface of the rectangular metal plate and the other being formed at another side of the holes on the top surface of the rectangular metal plate, wherein the respective rectangular waveguides of the waveguide horn array have a same size with the radiation patches, and each of the rectangular waveguides is coupled to the corresponding radiation patch. an antenna array comprising: a ground a dielectric substrate of a rectangular shape; a plurality of rectangular radiation patches arranged at intervals in the length direction of the dielectric substrate and formed on the top surface of the dielectric substrate; a plurality of coupling patches arranged in correspondence to the plurality of radiation patches, each of which formed on the top surface of the dielectric substrate and extending from a side of the dielectric substrate to a position spaced from a corresponding radiation patch by a distance; and a metal support arranged on the lower surface of the dielectric substrate and extending from an edge of the lower surface of the dielectric substrate downward to the ground, a layer of air having a predetermined thickness being formed between the dielectric substrate and the ground, and a dielectric substrate of a rectangular shape; a plurality of rectangular radiation patches arranged at intervals in the length direction of the dielectric substrate and formed on the top surface of the dielectric substrate; a plurality of coupling patches arranged in correspondence to the plurality of radiation patches, each of which formed on the top surface of the dielectric substrate and extending from a side of the dielectric substrate to a position spaced from a corresponding radiation patch by a distance; and a metal support arranged on the lower surface of the dielectric substrate and extending from an edge of the lower surface of the dielectric substrate downward to the ground, a layer of air having a predetermined thickness being formed between the dielectric substrate and the ground, and a waveguide horn array comprising: a rectangular metal plate having a cross section comprised of a plurality of rectangular holes arranged in the length direction of the rectangular metal plate, the lower part of each hole being formed as a rectangular waveguide, and the upper part of each hole being formed as a horn, and two grooves extending in the direction along which the plurality of holes are arranged and having a predetermined depth, one being formed at a side of the holes on the top surface of the rectangular metal plate and the other being formed at another side of the holes on the top surface of the rectangular metal plate, a rectangular metal plate having a cross section comprised of a plurality of rectangular holes arranged in the length direction of the rectangular metal plate, the lower part of each hole being formed as a rectangular waveguide, and the upper part of each hole being formed as a horn, and two grooves extending in the direction along which the plurality of holes are arranged and having a predetermined depth, one being formed at a side of the holes on the top surface of the rectangular metal plate and the other being formed at another side of the holes on the top surface of the rectangular metal plate,