Abstract: A filter includes a resonant circuit defining at least a portion of a signal path connected between a first terminal and a second terminal, an elastic wave resonator including one end that is grounded, a first inductor including one end connected to one end of the resonant circuit and another end connected to another end of the elastic wave resonator, and a second inductor including one end connected to another end of the resonant circuit and another end connected to the other end of the elastic wave resonator. The resonant circuit is an LC series resonant circuit in which a third inductor and first and second capacitors are connected in series with each other.

Abstract: A filter includes a resonant circuit defining at least a portion of a signal path connected between a first terminal and a second terminal, an elastic wave resonator including one end that is grounded, a first inductor including one end connected to one end of the resonant circuit and another end connected to another end of the elastic wave resonator, and a second inductor including one end connected to another end of the resonant circuit and another end connected to the other end of the elastic wave resonator. The resonant circuit is an LC series resonant circuit in which a third inductor and first and second capacitors are connected in series with each other.

Abstract: A high-frequency filter coupled between an input-output terminal and another input-output terminal includes series arm resonators, parallel arm resonators, and an inductor defining an LC resonant circuit. Frequencies at a first attenuation pole defined by resonant frequencies or anti-resonant frequencies of the series arm resonators and the parallel arm resonators and a frequency at a second attenuation pole defined by a resonant frequency of the LC resonant circuit are included in one stop band of the high-frequency filter, and the frequencies at the first attenuation pole are located closer than the frequency at the second attenuation pole to a pass band of the high-frequency filter.

Abstract: A high-frequency filter coupled between an input-output terminal and another input-output terminal includes series arm resonators, parallel arm resonators, and an inductor defining an LC resonant circuit. Frequencies at a first attenuation pole defined by resonant frequencies or anti-resonant frequencies of the series arm resonators and the parallel arm resonators and a frequency at a second attenuation pole defined by a resonant frequency of the LC resonant circuit are included in one stop band of the high-frequency filter, and the frequencies at the first attenuation pole are located closer than the frequency at the second attenuation pole to a pass band of the high-frequency filter.

Abstract: A high pass filter includes a first end connected to a first terminal and is a filter that transmits a signal in a first frequency band. A second terminal is connected to a second end of the high pass filter. A first switch includes a first end connected to the second end of the high pass filter. A third terminal is connected to a second end of the first switch. A low pass filter includes a first end connected to the first terminal and is a filter that transmits a signal in a second frequency band lower than the first frequency band. A fourth terminal is connected to a second end of the low pass filter. A second switch includes a first end connected to the second end of the low pass filter. A fifth terminal is connected to the second end of the second switch.

Abstract: A high frequency circuit module includes a variable inductance circuit portion and a reactance circuit portion. The variable inductance circuit portion is connected between an antenna port and ground. The variable reactance circuit is connected between the antenna port and a front-end port. The variable inductance circuit portion includes a first inductor, a second inductor, and a switch. The first inductor is connected between the antenna port and the ground. The second inductor and the switch are connected in series, and this series circuit is connected in parallel to the first inductor.

Abstract: A high pass filter includes a first end connected to a first terminal and is a filter that transmits a signal in a first frequency band. A second terminal is connected to a second end of the high pass filter. A first switch includes a first end connected to the second end of the high pass filter. A third terminal is connected to a second end of the first switch. A low pass filter includes a first end connected to the first terminal and is a filter that transmits a signal in a second frequency band lower than the first frequency band. A fourth terminal is connected to a second end of the low pass filter. A second switch includes a first end connected to the second end of the low pass filter. A fifth terminal is connected to the second end of the second switch.

Abstract: An antenna matching device includes an antenna terminal connected to an antenna and an RF terminal connected to an RF circuit. The antenna terminal and the RF terminal are connected to each other through a first transmission path only via an inductor. The antenna terminal and the RF terminal are connected to each other through a second transmission path only via an SPST switch. By switching between the open state and the closed state of the switch in accordance with the frequency of an RF signal, the first transmission channel or the second transmission channel is selected.

Abstract: A low-frequency radiating element and a high-frequency radiating element are configured so as to respectively operate in a relatively low frequency band and a relatively high frequency band that are non-contiguous with each other. A matching circuit is inserted between a transmission/reception circuit and a branching point. A high-frequency variable reactance circuit is inserted between the branching point and the high-frequency radiating element. A low-frequency variable reactance circuit is inserted between the branching point and the low-frequency radiating element. The high-frequency variable reactance circuit and the low-frequency variable reactance circuit are configured such that their reactances can be adjusted independently of each other.

Abstract: A high frequency circuit module includes a variable inductance circuit portion and a reactance circuit portion. The variable inductance circuit portion is connected between an antenna port and ground. The variable reactance circuit is connected between the antenna port and a front-end port. The variable inductance circuit portion includes a first inductor, a second inductor, and a switch. The first inductor is connected between the antenna port and the ground. The second inductor and the switch are connected in series, and this series circuit is connected in parallel to the first inductor.

Abstract: An antenna matching device includes an antenna terminal connected to an antenna and an RF terminal connected to an RF circuit. The antenna terminal and the RF terminal are connected to each other through a first transmission path only via an inductor. The antenna terminal and the RF terminal are connected to each other through a second transmission path only via an SPST switch. By switching between the open state and the closed state of the switch in accordance with the frequency of an RF signal, the first transmission channel or the second transmission channel is selected.

Abstract: A low-frequency radiating element and a high-frequency radiating element are configured so as to respectively operate in a relatively low frequency band and a relatively high frequency band that are non-contiguous with each other. A matching circuit is inserted between a transmission/reception circuit and a branching point. A high-frequency variable reactance circuit is inserted between the branching point and the high-frequency radiating element. A low-frequency variable reactance circuit is inserted between the branching point and the low-frequency radiating element. The high-frequency variable reactance circuit and the low-frequency variable reactance circuit are configured such that their reactances can be adjusted independently of each other.