| 摘要 |
An antenna device is provided which is capable of dealing with two or more frequencies or of carrying out communications using two or more communication methods by a single antenna and of controlling its directivity and, therefore, of achieving improvements in communication performance of the antenna device. The antenna device is so constructed that its shape is freely changed and its directivity can be changed to deal with a signal in any frequency band. The antenna device is made up of two or more antenna elements and switches which put each of the antenna elements into a connected or disconnected state. By controlling the switches, a shape of the antenna is changed so as to have a 90-degree bent dipole configuration to provide directivity, and a length of the antenna is changed so as to allow a changeover of a frequency band. The antenna device has a reflector being similar to the dipole-type antenna, which enables improvements in its directivity.
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