A radio-frequency filter includes a series-arm circuit on a circuit path that connects a first input/output terminal and a second input/output terminal. A parallel-arm circuit is connected to a node on the path and ground. The series-arm circuit includes a first impedance element, a first switch element connected to the first impedance element, and a series-arm resonator connected in parallel to the first impedance element and the first switch element. The parallel-arm circuit includes a first parallel-arm resonator, and a first switch circuit connected in series to the first parallel-arm resonator, the first switch circuit includes a second switch element. The first and second switch elements and the second switch elements include one or more transistors, and a gate width of the transistors included in the second switch element is larger than that of at least one of the transistors included in the first switch element.

An adjustable inductor including a toroidal core defining a plurality of gaps, a compressible gap material positioned in the gaps, at least one winding wound on the core, a force-applying structure, and a film substantially covering the adjustable inductor. The force-applying structure is operable to apply a force to the core to adjust the gaps and thereby an inductance of the adjustable inductor. The film is configured to prevent movement of force-applying structure when above a predetermined temperature threshold, and allow movement of the force-applying structure when below the predetermined threshold.

Reducing harmonics in a radio transmitter can involve using an electronically tunable harmonic filter (ETHF) in a transmit path at the output of an RF power amplifier stage to reduce harmonic signal components in the RF transmit signal. At least one filter characteristic of the ETHF is selectively controlled using one or more RF switch. The one or more RF switches that are used to control the ETHF can include a CMOS-SOI and/or a MEMs type of switch. Various filter characteristics of the ETHF can be controlled including a bandwidth and/or a center frequency of the ETHF.

A radio-frequency module is provided that includes a structure, a filtering element disposed on the structure, a switching element embedded in the structure, and an impedance element connected to the switching element and the filtering element. In a plan view of the structure, the switching element and the filtering element overlap each other in at least part thereof. The structure has a plurality of vias including a via , a via and a via. The via connects the input-output terminal and the filtering element. The via connects the ground terminal and an impedance adjustment circuit including the switching element and the impedance element. In a plan view, the via is located in a smallest rectangular region encompassing the vias.

A technique relates to a lossless microwave switch discussed herein. Multiple ports are included in the lossless microwave switch. Tunable filters are included in the lossless microwave switch. Each of the ports is operatively coupled a corresponding one of the tunable filters.

In accordance with an embodiment, an RF system includes a transmit path having a first tunable transmit band stop filter, and a power amplifier coupled to an output of the first tunable transmit band stop filter, where the first tunable transmit band stop filter is configured reject a receive frequency and pass a transmit frequency; a receive path comprising an LNA; and a duplex filter having a transmit path port coupled to an output of the power amplifier, a receive path port coupled to an input of the LNA, and an antenna port, where the duplex filter is configured to pass the transmit frequency and reject the receive frequency between the antenna port and the transmit path port, pass the receive frequency and reject the transmit frequency between the antenna port and the receive path port.

Reducing harmonics in a radio transmitter can involve using an electronically tunable harmonic filter (ETHF) in a transmit path at the output of an RF power amplifier stage to reduce harmonic signal components in the RF transmit signal. At least one filter characteristic of the ETHF is selectively controlled using one or more RF switch. The one or more RF switches that are used to control the ETHF can include a CMOS-SOI and/or a MEMs type of switch. Various filter characteristics of the ETHF can be controlled including a bandwidth and/or a center frequency of the ETHF.

A package for a tunable filter is disclosed. In an embodiment, the tunable filter includes a substrate having a first interconnection plane and a semiconductor device assembled on the substrate in a first component plane, the semiconductor device electrically connected to the first interconnection plane and containing tunable passive components. The filter further includes a control unit arranged in the first component plane, a dielectric layer arranged above the first component plane, a second component plane arranged on the dielectric layer and discrete passive devices arranged in the second component plane and interconnected with the semiconductor device, wherein the tunable passive components are tunable by the control unit.

An adjustable inductor including a toroidal core defining a plurality of gaps, a compressible gap material positioned in the gaps, at least one winding wound on the core, a force-applying structure, and a film substantially covering the adjustable inductor. The force-applying structure is operable to apply a force to the core to adjust the gaps and thereby an inductance of the adjustable inductor. The film is configured to prevent movement of force-applying structure when above a predetermined temperature threshold, and allow movement of the force-applying structure when below the predetermined threshold.

Apparatus and methods for tunable filtering are provided. In certain embodiments, a tunable filter is implemented using one or more controllable capacitors formed on a semiconductor die and using one or more shielded integrated inductors formed on a secondary circuit board that attaches to a carrier circuit board. Additionally, the shielded integrated inductors are formed from patterned metallization layers of the secondary circuit board, and shielding is provided on the secondary circuit board and/or the carrier circuit board to shield the inductors from the semiconductor die and/or other components.