| 摘要 |
An antenna in which first and second antenna elements are selected by a switching apparatus so that the first and the second antenna elements are connected to an unbalanced transmission line via a balancing-unbalancing transmission line or only the first antenna element is connected to the unbalanced transmission line. The unbalanced transmission line supplies power via a balanced-to-unbalanced transformation apparatus to the first and the second antenna elements, so as to operate as an antenna, at which time, balanced-to-unbalanced transformation action of the balanced-to-unbalanced transformation apparatus prevents leakage current from flowing from the first or the second antenna element to the unbalanced transmission line and prevents a ground element on which the unbalanced transmission line is grounded from operating as an antenna. This reduces deterioration of antenna characteristics in the vicinity of a human body, so that an antenna device and portable radio set which can sizably reduce deterioration of communication quality can be realized.
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