Antenna, radio device, method of designing antenna, and method of measuring operating frequency of antenna

摘要

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.