Abstract: A directional coupler includes a main line, a first sub-line, a second sub-line, a first phase shift circuit, a first short-circuit path, and a first short-circuit switch. The first phase shift circuit is connected between the first sub-line and the second sub-line. The first short-circuit path short-circuits both ends of the first phase shift circuit. The first short-circuit switch switches between conduction and non-conduction of the first short-circuit path.

Abstract: A directional coupler includes a first main line, a second main line, first sub-lines, second sub-lines, a first output terminal, a second output terminal, a first inductor, and a second inductor. The first output terminal is configured to be coupled to the first sub-lines. The first output terminal is configured to output a first detection signal corresponding to a first radio-frequency signal transferred through the first main line. The second output terminal is configured to be coupled to the second sub-lines. The second output terminal is configured to output a second detection signal corresponding to a second radio-frequency signal transferred through the second main line. The first inductor is provided in a first signal path including the first output terminal. The second inductor is provided in a second signal path including the second output terminal.