Patent ID: 8836603

Claim:
An antenna device comprising: a grounded metal plate; a linear first metal wire arranged vertically to the metal plate; a power feeding or receiving portion that is provided between the first metal wire and the metal plate and that is adapted to feed or receive power to or from a plurality of linear second metal wires; the plurality of second metal wires having first ends which are connected to the first metal wire, the plurality of second metal wires being radially arranged around the first metal wire, and extending in a direction parallel to the metal plate; third metal wires connected to second ends of the second metal wires opposite to the first ends of the second metal wires connected to the first metal wire, the third metal wires being vertical to the metal plate; and variable impedance elements comprising variable resistance elements that connect the third metal wires to the metal plate, wherein loops are formed by the first, second and third metal wires and electrical mirror images of the first, second, and third metal wires formed by the metal plate, and wherein the resistance of each variable resistance element is variable, thereby a reflection amount and an absorption amount of radio waves propagating through the third metal wires are varied, wherein the reflection amount comprises an amount of radio waves reflected at each of connecting points of the third metal wires and corresponding variable resistance elements, and the absorption amount comprises an amount of radio waves absorbed by each of the variable resistance elements, thereby the distribution of radio waves in the second metal wires and the third metal wires is variable, and thereby the directivity of the antenna device in a plane perpendicular to the first metal wire is variable.