A high-frequency switch includes an input interface configured to receive a high-frequency signal; an output interface configured to output the high-frequency signal to outside; and a reactance switch inserted between the input interface and the output interface. The reactance switch includes a plurality of reactance circuits connected in a cascade arrangement between the input interface and the output interface. Each of the plurality of reactance circuits is configured to form a common passband for the high-frequency signal based on a reactance of a respective predetermined values, and at least one of the reactance circuits is a variable reactance circuit having a reactance which changes in response to a control signal input from the outside so that the passband of the variable reactance circuit changes.

A switch module includes a first terminal, first and second filters, and first and second switches. Impedance of the first filter for a signal in a stop band is capacitive. When the first switch is turned OFF, impedance of the first switch is capacitive, and impedance of the first filter seen from an end portion of the first switch connected to the first filter is not in a short state and impedance of the first filter seen from the first terminal is in an open state.

A front end module includes a base filter configured to operate as a bandpass filter passing a pass band of an input radio frequency signal; a switch connected to the base filter, and a first notch filter and a second notch filter selectively connected to the base filter through the switch, wherein a stop band of the first notch filter and a stop band of the second notch filter overlap the pass band of the base filter in a band equal to or higher than a center frequency of the pass band of the base filter.

Provided is a low-leakage automatic adjustable diplexer including a body, a thin plate and two resonant regulators. The body has therein cuboid waveguide channels each having a feeding portion, a reception port portion, a transmission port portion, a fitting portion, a first filtering portion, a second filtering portion, first E/H conversion units connected to two ends of the first filtering portion, respectively, and second E/H conversion units connected to two ends of the second filtering portion, respectively. The thin plate is clamped inside the body. The resonant regulators each have a plurality of frequency disturbance elements adjustably protruding into the first and second filtering portions. Given the E/H conversion units and the frequency disturbance elements penetratingly disposed on the H-side sidewall of the cuboid waveguide cavity, it is unnecessary for the cuboid waveguide channels to undergo any processing process for forming therein any protrusion-style insulation walls, thereby attaining low leakage.

An integrated isolator circuit for isolating receiver and transmitter in a Time-Division Duplex transceiver is disclosed. The integrated isolator circuit comprises a first node, a second node and a third node. The integrated isolator circuit further comprises a first capacitor connected in series with a first switch and connected between the first and second nodes. The integrated isolator circuit further comprises a first inductor connected between the first and second nodes and a second capacitor connected between the second node and the third node. The first switch has an on state and an off state, and the integrated isolator circuit is configured to have a different impedance at a certain operating frequency by controlling the state of the first switch.

A radio frequency module includes a transmit filter of Band A and Band B, a transmit amplifier, and a switch circuit and can perform CA using a transmit signal of Band A and a receive signal of Band B, a transmit band of Band B including a receive band of Band C. The switch circuit includes a switch switching connection between a common terminal and a first selection terminal, a switch switching connection between the common terminal and a second selection terminal, and a switch switching connection between the second selection terminal and a third selection terminal. The common terminal is connected to the transmit amplifier. The first selection terminal is connected to the transmit filter of Band A. The second selection terminal is connected to the transmit filter of Band B. The third selection terminal is connected to a receive path of Band C.

A high frequency amplification circuit includes transmission amplification circuits 11 and 12; a transmission filter D-Tx whose pass band is a band D of a first frequency band group; transmission filters E-Tx and G-Tx whose pass bands are respectively bands E and G of a second frequency band group; an output matching circuit 31 configured to match the transmission amplification circuit 11 and the transmission filter D-Tx; and an output matching circuit 32 configured to match the transmission amplification circuit 12 and the transmission filters E-Tx and G-Tx. The band D is positioned at a high frequency-side end portion of the first frequency band group, and the band E is positioned at a low frequency-side end portion of the second frequency band group. The output matching circuit 31 includes a low-pass circuit, and the output matching circuit 32 includes an impedance-variable circuit.

A filter includes a first resonant circuit having one or more first resonant frequencies, a second resonant circuit having one or more second resonant frequencies different from the first resonant frequency, and a switch connected to the first resonant circuit and the second resonant circuit. The switch switches between a first state in which a radio-frequency signal of the first resonant frequency flows from an IN terminal to an OUT terminal via the first resonant circuit and a radio-frequency signal of the second resonant frequency flows from the IN terminal to ground via the second resonant circuit and a second state in which a radio-frequency signal of the first resonant frequency flows from the IN terminal to ground via the first resonant circuit and a radio-frequency signal of the second resonant frequency flows from the IN terminal to the OUT terminal via the second resonant circuit.

Methods and system for using a multifunctional filter to minimize insertion loss in a multi-mode communications system are described. Specifically described is a multifunctional filter that is configurable to operate in a band-pass mode when a first type of signal is propagated through the multifunctional filter, and to operate in a low-pass mode when a second type of signal is propagated through the multifunctional filter. The multifunctional filter presents a lower insertion loss to the second type of signal when operating in the low-pass mode than in the band-pass mode.

A multiplexer includes: a multilayered body including dielectric layers stacked and having first and second surfaces; a common terminal, a first terminal, a second terminal, and a ground terminal disposed on a surface of the multilayered body; a first filter disposed in the multilayered body and electrically connected between the common terminal and the first terminal; a second filter including: a first inductor electrically connected between the common terminal and the second terminal; and a second inductor connected in series with the first inductor between the first inductor and the second terminal, the second inductor at least partially overlapping with the first inductor, a capacitance between a first end of the second inductor electrically closer to the common terminal and the ground terminal being larger than a capacitance between a first end of the first inductor electrically closer to the common terminal and the ground terminal.