A configurable 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. Each of the group of RF RX bandpass filters is coupled to a first common connection node. Each of the group of RF TX switching elements is coupled between a corresponding one of the group of RF TX bandpass filters and the first common connection node, which is coupled to a first RF antenna.

An apparatus includes an impedance circuit and a plurality of inductors coupled to the impedance circuit. Each of the plurality of inductors is coupled in parallel to a corresponding switch of a plurality of switches.

A radio frequency (RF) circuit is described that comprises a plurality of switching arms selectively activatable and associated with corresponding RF input ports. A switch source impedance is associated with each of the RF input ports. The switch source impedance is frequency dependent with its value matched to a characteristic impedance value within a first frequency range. The value of the switch source impedance is not matched to the characteristic impedance value within a second frequency range. When an RF signal within the first frequency range is transmitted through the RF circuit, between one of the RF input ports and an a common port, an RF distortion voltage within a distortion frequency range results at the common port; and the amplitude of a resultant RF distortion voltage is lower than an RF distortion voltage if the switched source impedance is matched to the characteristic impedance within the second frequency range.

A tunable duplexer circuit is described, wherein the frequency response as well as bandwidth and transmission loss characteristics can be dynamically altered, providing improved performance for transceiver front-end applications. The rate of roll-off of the frequency response can be adjusted to improve performance when used in duplexer applications. A method is described where the duplexer circuit characteristics are optimized in conjunction with a specific antenna frequency response to provide additional out-of-band rejection in a communication system. Dynamic optimization of both the duplexer circuit and an active antenna system is described to provide improved out-of-band rejection when implemented in RF front-end circuits of communication systems. Other features and embodiments are described in the following detailed descriptions.

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 filter is provided that includes a set of cascaded resonator stages coupled between a filter input and a first filter output, wherein the filter includes a second filter output coupled to an output of a first or an intermediate one of the set of cascaded resonator stages. Another filter includes a set of cascaded resonator stages coupled between a first filter input and a filter output, wherein the filter includes a second filter input coupled to an input of an intermediate or a last one of the set of cascaded resonator stages. Both filters are configured to apply a first filter frequency response to a first signal propagating via the set of cascaded resonator stages, and apply a second filter frequency response to a second signal propagating via a subset of one or more of the set of cascaded resonator stages.

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.

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 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.

An aspect of the disclosure relates to a receiver, including: a low noise amplifier (LNA); and an input stage coupled to the LNA, wherein the input stage is configured to provide a first passband for a first signal across at least a portion of a first frequency band and a notch to substantially reject a second signal within the first frequency band or a second frequency band in accordance with a first mode of operation, and a second passband for the second signal across the second frequency band in accordance with a second mode of operation. In the first mode, the input stage includes a parallel L-C resonance frequency and an L-match impedance matching circuit. In the second mode, the input stage includes a modified bridge T-coil impedance matching circuit with substantially no electromagnetic coupling between the inductors of the circuit.