An antenna comprises a first conductive layer, a second conductive layer
and an LC resonance circuit. The first conductive layer has plural
elements and is disposed adjacently to each other. The second conductive
layer is disposed at a predetermined distance from the first conductive
layer via a dielectric substrate. The LC resonance circuit comprises
connection for electrically connecting the elements and the second
conductive layer. The LC resonance circuit takes a resonance state in
which impedance becomes high in the operating frequency of the antenna.
Of the plural elements, a power feeding section is provided in each of
any two adjacent elements. Power is fed to the power feeding sections
during transmission so that signals of the operating frequency are
opposite in phase, and signals of the operating frequency inputted to the
antenna are outputted in opposite phase from the power feeding sections
during reception.