Abstract: A radio frequency circuit includes a multilayer substrate, series arm circuits in a first path connecting the input/output terminals (T1 and T2) on the multilayer substrate, a parallel arm circuit in a second path connecting a node on the first path and a ground, a wiring A on the multilayer substrate connected to the input/output terminal (T1) as a part of the first path, a wiring B on the multilayer substrate connected to the input/output terminal (T2) as a part of the first path, and a wiring C on the multilayer substrate as a part of the second path. The parallel arm circuit includes an impedance variable circuit, the wiring A and the wiring B in a layer different from the multilayer substrate. When viewed in a plan view, the wiring C does not overlap with the wiring A and the wiring B.

Abstract: A multiplexer capable of concurrently sending a radio-frequency signal in one of Band A and Band B belong to a low band group and a radio-frequency signal in a Band C belongs to a high band group that includes: a common terminal and input/output terminals; a low-pass filter arranged between the common terminal and the input/output terminal and whose pass band is frequencies in the low band group and whose attenuation band is frequencies in the high band group; and a high-pass filter arranged between the common terminal and the input/output terminal and whose pass band is the frequencies in the high band group and whose attenuation band is the frequencies in the low band group. The low-pass filter includes a first frequency-variable circuit including a switch, and at least one of the pass band and the attenuation band of the low-pass filter is changeable.

Abstract: A multilayer substrate includes a dielectric substrate, a pair of capacitor electrodes, and an input/output electrode that is an electrode for input, an electrode for output, or an electrode for input and output. The dielectric substrate has a first main surface and a second main surface that are opposite to each other in a thickness direction of the dielectric substrate. The pair of capacitor electrodes is disposed in the dielectric substrate. Electrodes of the pair of capacitor electrodes face each other in the thickness direction. The input/output electrode is disposed on the second main surface of the dielectric substrate. A capacitor that includes the pair of capacitor electrodes and a portion being part of the dielectric substrate and located between the electrodes of the pair of capacitor electrodes at least partially overlaps the input/output electrode electrically connected to the capacitor.

Abstract: A filter device (100) includes a flat-shaped insulator (20), a filter (FLT1) that is disposed at the insulator (20) and is configured to pass a radio-frequency signal and a switching circuit (SWIC) configured to change at least one of a pass band and an attenuation band of the filter (FLT1). A control line (62 or 63) configured to supply driving power or a control signal to the switching circuit (SWIC) is formed at the insulator (20). The control line (62 or 63) is disposed so as not to overlap a radio-frequency line that passes a radio-frequency signal in the filter (FLT1) when the insulator (20) is viewed in plan.

Abstract: A multilayer substrate includes a dielectric substrate, a pair of capacitor electrodes, and an input/output electrode that is an electrode for input, an electrode for output, or an electrode for input and output. The dielectric substrate has a first main surface and a second main surface that are opposite to each other in a thickness direction of the dielectric substrate. The pair of capacitor electrodes is disposed in the dielectric substrate. Electrodes of the pair of capacitor electrodes face each other in the thickness direction. The input/output electrode is disposed on the second main surface of the dielectric substrate. A capacitor that includes the pair of capacitor electrodes and a portion being part of the dielectric substrate and located between the electrodes of the pair of capacitor electrodes at least partially overlaps the input/output electrode electrically connected to the capacitor.

Abstract: A multiplexer capable of concurrently sending a radio-frequency signal in one of Band A and Band B belong to a low band group and a radio-frequency signal in a Band C belongs to a high band group that includes: a common terminal and input/output terminals; a low-pass filter arranged between the common terminal and the input/output terminal and whose pass band is frequencies in the low band group and whose attenuation band is frequencies in the high band group; and a high-pass filter arranged between the common terminal and the input/output terminal and whose pass band is the frequencies in the high band group and whose attenuation band is the frequencies in the low band group. The low-pass filter includes a first frequency-variable circuit including a switch, and at least one of the pass band and the attenuation band of the low-pass filter is changeable.

Abstract: A radio frequency circuit includes a multilayer substrate, series arm circuits in a first path connecting the input/output terminals (T1 and T2) on the multilayer substrate, a parallel arm circuit in a second path connecting a node on the first path and a ground, a wiring A on the multilayer substrate connected to the input/output terminal (T1) as a part of the first path, a wiring B on the multilayer substrate connected to the input/output terminal (T2) as a part of the first path, and a wiring C on the multilayer substrate as a part of the second path. The parallel arm circuit includes an impedance variable circuit, the wiring A and the wiring B in a layer different from the multilayer substrate. When viewed in a plan view, the wiring C does not overlap with the wiring A and the wiring B.