High-frequency front-end circuit

A high-frequency front-end circuit, comprising:

• first and second variable filters each including an adjustable transmission characteristic and an adjustable impedance characteristic;
• a common terminal to which the first variable filter and the second variable filter are connected;
• a first individual terminal that is connected to a side of the first variable filter opposite to a side to which the common terminal is connected;
• and
• a second individual terminal that is connected to a side of the second variable filter opposite to the side to which the common terminal is connected;
• wherein
• at a time when frequency division duplex communication signals are to be transmitted and received, a band characteristic of the first variable filter is set such that a transmission frequency band falls within a pass band of the first variable filter and a reception frequency band falls within an attenuated band of the first variable filter, and a band characteristic of the second variable filter is set such that the reception frequency band falls within a pass band of the second variable filter and the transmission frequency band falls within an attenuated band of the second variable filter;
• at a time when time division duplex communication signals are to be transmitted, the pass band of the first variable filter is adjusted to match a transmission frequency band and an impedance of the second variable filter is adjusted such that the impedance of the second variable filter in the transmission frequency band seen from the common terminal side is open;
• and
• at a time when the time division duplex communication signals are to be received, the pass band of the second variable filter is adjusted to match a reception frequency band and an impedance of the first variable filter is adjusted such that the impedance of the first variable filter in the second frequency band seen from the common terminal side is open.