A high-frequency transformer includes a primary coil and a secondary coil coupled to each other by magnetic field coupling and sharing a coil winding axis, a first terminal connected to a first end of the primary coil, a second terminal connected to a first end of the secondary coil, and a common terminal connected to a second end of the primary coil and a second end of the secondary coil. The primary and secondary coils are helical coils including loop conductor patterns, and the number of turns of a first loop conductor pattern closest to the second end of the primary coil is larger than an average number of turns of other loop conductor patterns included in the primary coil.

Methods and apparatuses are provided for a matched band pass filter utilized in a duplexer or multiplexer. In one embodiment, the matched band pass filter includes a filter part and a port-matching part that is coupled to and in signal communication with the filter part. The filter part is configured to filter an RF signal and includes an input port. The port-matching part includes an output port. The port-matching part is configured to provide impedance matching through the output port.

A diplexer includes a low-band band pass filter between a common input/output terminal and a low-band input/output terminal and a high-band band pass filter between the common input/output terminal and a high-band input/output terminal, wherein the low-band band pass filter includes LC resonators including a first-stage LC resonator to a final-stage LC resonator in order from the common input/output terminal toward the low-band input/output terminal, the high-band band pass filter includes LC resonators including a first-stage LC resonator to a final-stage LC resonator in order from the common input/output terminal toward the high-band input/output terminal, a matching capacitor is between the common input/output terminal and the low-band band pass filter, and the capacitance of a capacitor of the first-stage LC resonator of the low-band band pass filter is smaller than the capacitance of a capacitor of the final-stage LC resonator.

A reconfigurable microacoustic filter is specified which comprises a ladder-type-like filter topology and a suitably placed adjustable capacitive element.

The present disclosure provides a radio frequency duplexer circuit and a radio frequency substrate. The radio frequency duplexer circuit includes a first terminal, a second terminal, a third terminal, a low-pass filter, and a high-pass filter. The low-pass filter includes N first filter sub-circuits coupled in series and a first tuning sub-circuit. Among the N first filter sub-circuits coupled in series, a first end of a 1.sup.st first filter sub-circuit is coupled to the first terminal, and a second end of a N.sup.th first filter sub-circuit is coupled to the second terminal. The high-pass filter includes M second filter sub-circuits coupled in series and a second tuning sub-circuit. Among the M second filter sub-circuits coupled in series, a first end of a 1.sup.st second filter sub-circuit is coupled to the first terminal, and a second end of a M.sup.th second filter sub-circuit is coupled to the third terminal.

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 this disclosure relate to a multiplexer with a hybrid acoustic passive filter. The multiplexer includes a plurality of filters configured to filter respective radio frequency signals, a shared filter coupled between each of the plurality of filters and a common node, and a radio frequency filter coupled to the common node. At least a first filter of the plurality of filters includes acoustic resonators and a non-acoustic passive component. Related multiplexers, wireless communication devices, and methods are disclosed.

Circuits with filters and acoustic resonators. In some embodiments, a radio-frequency circuit can include a plurality of nodes and a common node. The radio-frequency circuit can further include a signal path implemented between each of the plurality of nodes and the common node. Each corresponding signal path can include a filter having a first Q-factor value and a respective resonator having a second Q-factor value higher than the first Q-factor value.

Provided is a frequency multiplexer. The frequency multiplexer includes a stacked structure. The stacked structure includes at least one insulating layer and a plurality of metal layers arranged alternately along a stacked direction. The stacked structure forms at least one first inductive element and at least one capacitive element. At least two of the plurality of metal layers are provided with respective first patterned metal structures. The first patterned metal structures in the at least two of the plurality of metal layers are electrically connected to form a first multilayer planar spiral coil structure. The first multilayer planar spiral coil structure constitutes the first inductive element.

A diplexer includes a common terminal, first and second terminals, and first and second filters which are electrically connected to the common terminal. The first filter passes a high frequency signal in a first frequency band. The second filter passes a high frequency signal in a second frequency band higher than the first frequency band. Each filter includes an inductor and a capacitor in a dielectric substrate. The first filter includes a first inductor with one end electrically connected to the common terminal, and a first capacitor electrically connected between another end of the first inductor and a ground. An inductance of the first inductor is smaller than an inductance of another inductor included in the first filter. A frequency of an attenuation pole defined by the first inductor and the first capacitor is higher than a frequency of the second frequency band.