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.

Aspects of the disclosure relate to wireless communication, and high-frequency filters with resonators configured to systematically modify phase characteristics of an antenna reflection coefficient. One example is a wireless communication apparatus for a multi-band system comprising a frequency band filter circuit having a filter passband that includes a first band of the multi-band system. The frequency band filter circuit comprises a plurality of resonators coupled between an antenna port and a signal port and a resonant structure electrically coupled to the plurality of resonators. The resonant structure has a resonance outside of the first band and a second band of the multi-band system, the resonance being closer to the second band than to the first band.

Systems, methods, and devices for operating in either frequency division duplexing (FDD) or time division duplexing (TDD) for wireless communications using the same electrical balance duplexer (EBD) circuitry in a transceiver device are provided. A series of switches may selectively couple components of the EBD, such as a low noise amplifier (LNA), a power amplifier (PA), and balancing impedance, to ground based on selected operation mode (e.g., FDD or TDD) while reducing insertion loss of the receiver (RX) and transmitter (TX) signals. Tuned matching network blocks for the LNA and PA may be used in addition to the series of switches to provide impedance matching for additional reduction of insertion loss.

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 switchable RF transmit/receive (TX/RX) multiplexer, which includes a group of RF TX bandpass filters, a group of RF TX switching elements, and a group of RF RX bandpass filters; is disclosed. The group of RF TX bandpass filters includes a first RF TX bandpass filter and a second RF TX bandpass filter, such that each of the first RF TX bandpass filter and the second RF TX bandpass filter is coupled to a first filter connection node. The group of RF TX switching elements includes a first RF TX switching element coupled between the first filter connection node and a first common connection node, which is coupled to a first RF antenna. Each of the group of RF RX bandpass filters is coupled to the first common connection node.

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.

Embodiments relate to a transformer-based impedance matching network that may dynamically change its characteristic impedance by engaging different inductor branches on a primary side and optionally, on the secondary side. A primary side transformer circuit includes a primary inductor (311) and secondary inductor (321) configured to provide impedance matching over a first frequency band. One or more additional inductor branches (314A, 314B, are switchably coupled to either or both of the primary and secondary inductors to modify the impedance matching characteristics over additional operating frequencies. One or more LC filter branches (321, 322, 326, 327, 336, 330) can be included at the output of the secondary side to filter harmonic frequencies in each of the operating frequency bands.

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 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 multiplexer (100) includes a first filter (FLT1) that passes a signal in a first frequency band, a second filter (FLT2) that passes a signal in a second frequency band lower than the first frequency band, and a third filter (FLT3) that passes a signal in a third frequency band. The third frequency band is a frequency band higher than the first frequency band, or a frequency band lower than the second frequency band. The first filter includes a first inductor (L11) that forms a first attenuation pole on a low-frequency side of the first frequency band. The second filter includes a second inductor (L23) that forms a second attenuation pole on a high-frequency side of the second frequency band. At least a portion of a component constituting the third filter is disposed between the first inductor and the second inductor.