Variable capacitance circuit, variable capacitance thin film capacitor and radio frequency device

A variable capacitance thin film capacitor device comprising:

• first to Nth variable capacitance elements formed on a supporting substrate that are sequentially connected in series, whose capacitances change depending on voltage applied thereto;
• an ith bias line on an input terminal side provided between an input terminal portion of the first variable capacitance element and a connection point between a 2ith variable capacitance element and a (2i+1)th variable capacitance element;
• and
• an ith bias line on an output terminal side provided between an output terminal portion of the Nth variable capacitance element and a connection point between a (2i−1)th variable capacitance element and the 2ith variable capacitance element, where N and i are integers satisfying N=2n+1, n≧1, 1≦i ≦n,
• wherein the input terminal portion comprises a single input terminal that serves both as a signal input terminal for receiving radio frequency signals and an input terminal for application of direct current bias.

A radio frequency device comprising a resonant circuit which includes in part a variable capacitance thin film capacitor device comprising first to Nth variable capacitance elements formed on a supporting substrate that are sequentially connected in series, whose capacitances change depending on voltage applied thereto, the radio frequency device comprising:

• an ith bias line on an input terminal side provided between an input terminal portion of the first variable capacitance element and a connection point between a 2ith variable capacitance element and a (2i+1)th variable capacitance element;
• and
• an ith bias line on an output terminal side provided between an output terminal portion of the Nth variable capacitance element and a connection point between a (2i−1)th variable capacitance element and the 2ith variable capacitance element, where N and i are integers satisfying N=2n+1, n≧1, 1≦i≦n,
• wherein the input terminal portion comprises a single input terminal that serves both as a signal input terminal for receiving radio frequency signals and an input terminal for application of direct current bias.

A radio frequency device comprising a variable capacitance thin film capacitor device for use as a capacitance element for coupling a plurality of resonant circuits, the variable capacitance thin film capacitor device comprising first to Nth variable capacitance elements formed on a supporting substrate that are sequentially connected in series, whose capacitances change depending on voltage applied thereto, the radio frequency device comprising:

• an ith bias line on an input terminal side provided between an input terminal portion of the first variable capacitance element and a connection point between a 2ith variable capacitance element and a (2i+1)th variable capacitance element;
• and
• an ith bias line on an output terminal side provided between an output terminal portion of the Nth variable capacitance element and a connection point between a (2i−1)th variable capacitance element and the 2ith variable capacitance element, where N and i are integers satisfying N=2n+1, n≧1, 1≦i≦n,
• wherein the input terminal portion comprises a single input terminal that serves both as a signal input terminal for receiving radio frequency signals and an input terminal for application of direct current bias.