Patent ID: 7538732

Claim:
An antenna structure comprising: a circuit for radio communication; a dielectric base member; a feed radiation electrode provided on the dielectric base member and connected to the circuit for radio communication, the feed radiation electrode performing an antenna operation in a fundamental mode with a lowest resonant frequency among a plurality of resonant frequencies of the electrode and an antenna operation in a higher-order mode with a resonant frequency higher than the resonant frequency in the fundamental mode, wherein: the feed radiation electrode has a spiral shape such that the feed radiation electrode extends in a direction away from a feed point connected to the circuit for radio communication and then turns to approach the feed point, a first end of the feed radiation electrode defining a feed end connected via the feed point to the circuit for radio communication, and a second end of the feed radiation electrode defining an open end; a ground-level voltage region in the higher-order mode located electrically proximal to the open end of the feed radiation electrode defining a capacitance-loading portion; and a capacitance-loading conductor that extends from the capacitance-loading portion in a direction toward the feed end, the capacitance-loading conductor forming a capacitance for adjusting the resonant frequency in the fundamental mode between the feed end of the feed radiation electrode and the capacitance-loading portion.