Patent ID: 7557773

Claim:
A variable tuning antenna comprising: a radiation element; and a tuning circuit connected to the radiation element in series, the tuning circuit comprising a first inductance element and a parallel circuit which is connected to the first inductance element in series, the parallel circuit comprising a second inductance element and a variable capacitance element connected to each other in parallel, wherein the tuning circuit is formed so as to be tunable in the desired frequency band by varying the capacitance of the variable capacitance element, and the tuning circuit is set so that a combined reactance of the radiation element and the first inductance element and a combined reactance of the parallel circuit are canceled by each other, and the parallel circuit does not resonate in a desired receiving frequency band, and wherein the radiation element comprises a first antenna element and a second antenna element connected to each other electrically in series, one end of the second antenna element that is opposite to the first antenna element being connected to a feeding part through the tuning circuit, the first antenna element and the second antenna element being formed in an electric length so as to resonate at a frequency within the desired frequency band by the total length, and so as to resonate at a first frequency band of a wide band in the desired frequency band with the tuning circuit, and a connecting part of the first antenna element and the second antenna element being directly connected to the feeding part without the tuning circuit, so as to resonate at a second frequency band, which is different from the first frequency band, and to be non-resonant in the first frequency band, by only the first antenna element.