Antenna device and antenna system

An antenna device comprising an antenna element which has an electrically conductive path continuing from one end part to the other end part and which has a feed section provided in the one and the other end parts of the electrically conductive path,

• the antenna element having a first root section which includes the one end part of the electrically conductive path, a second root section which includes the other end part of the electrically conductive path, and an intermediate section which lies between the first root section and the second root section,
• the feed section being provided in the first root section and the second root section,
• the first root section and the second root section being arranged, in a first region that is part of a region where the electrically conductive path is formed, so as to surround the feed section,
• in the first region, tail end linear parts of the respective first and second root sections, which tail end linear parts are directly connected with the intermediate section, extending in respective opposite directions, and
• at least one of the first and second root sections having a wider width part, the wider width part being formed such that a portion that overlaps a feed line connected with the feed section is larger in width than other portions.