Patent ID: 7136020
Filing Date: 2006-11-14
Classification: H01Q

Abstract:
1. An antenna structure suitable for multi-band radio communication, comprising: a feed radiation electrode having a plurality of resonance frequencies that are different from each other, the feed radiation electrode being arranged in proximity to a base plate, one end of the feed radiation electrode being a feed end portion at which a feeding electrode is disposed and connected to the one end of the feed radiation electrode, the other opposite end thereof being an open end portion; a ground portion disposed on the base plate; a ground connection line coupling the open end portion of the feed radiation electrode to the ground portion; a switch included in the ground connection line and being operative to selectively change one of an on-state of the ground connection line and an off-state of the ground connection line to the other of the on-state and the off-state; and a capacitance-rendering portion for rendering a capacitance between the open end portion of the feed radiation electrode and the ground portion; wherein when the ground connection line is changed from the off-state to the on-state of the connection by switching of the switch, a capacitance generated by the capacitance-rendering portion is rendered between the open end portion of the feed radiation electrode and the ground portion, such that the resonant frequency in a fundamental frequency band which is lowest of the plurality of frequency bands based on the antenna operation of the feed radiation electrode is reduced corresponding to the rendered capacitance, and when the ground connection line is changed from the on-state to the off-state of the connection by switching of the switch, the resonant frequency in the fundamental frequency band is increased corresponding to the decreased amount of the capacitance between the open end portion of the feed radiation electrode and the ground portion which is caused when the capacitance by the capacitance-rendering portion ceases to be rendered.