Patent ID: 7043269

Claim:
A communication card as a card-shaped communication device that is used being inserted into a card slot of an information device, said communication card including: an antenna operable to receive or output communication waves; and an antenna matching means for establishing a conjugate match between an input impedance of said antenna and an output impedance of a matching circuit so as to have resistances which are equal to each other and reactances which have opposite signs but equal absolute values, said antenna being placed to be electromagnetically coupled with a metallic body which constitutes the information device, via an internal wall of the card slot, and said antenna matching means comprising: a variable matching unit operable to vary a circuit parameter in accordance with a control signal; a directional coupling unit operable to extract a reflected signal from said antenna; a detection unit operable to detect an amplitude of the reflected signal that is extracted by said direction coupling unit; and a control unit operable to output the control signal to said variable matching unit on the basis of the amplitude of the reflected signal that is detected by said detection unit.