VARIABLE CAPACITANCE ELEMENT, AND BOOSTER ANTENNA AND READER/WRITER PROVIDED THEREWITH

PROBLEM TO BE SOLVED: To provide a variable capacitance element, and booster antenna and reader/writer provided therewith capable of restraining data leakage of the IC card and other contactless media and improving the security, in a fuss-free and by a convenient method. SOLUTION: The variable capacitance element comprises a pair of electrodes, a closed section provided between the electrodes, and a first medium contained in the closed section and a second medium with a permittivity which is different from that of the first medium, and changes its capacitance, according to its rotational position. The booster antenna and reader/writer provided with the variable capacitance element is capable of changing the resonance frequency, according to the rotational position, thereby data communication between a contactless communication medium and the reader/writer can be controlled and data leakage unintended by a holder of the contactless medium can be restrained. COPYRIGHT: (C)2009,JPO&INPIT