A differential amplification circuit includes a differential amplifier configured to output a signal including harmonics and first and second filters configured to reduce level of an even harmonic included in output from the differential amplifier. The first and second filters are connected to output of the differential amplifier. The first filter includes a resonant circuit composed of a capacitor and an inductor and a resonant circuit composed of a capacitor and the inductor. The second filter includes a resonant circuit composed of a capacitor and an inductor and a resonant circuit composed of a capacitor and the inductor. A center frequency of the first filter is lower than a center frequency of the even harmonic. A center frequency of the second filter is higher than the center frequency of the even harmonic.

A branching filter includes a common port, a first signal port, a second signal port, a first filter, which is provided between the common port and the first signal port, that selectively passes a signal of a frequency within a first passband, a second filter, which is provided between the common port and the second signal port, that selectively passes a signal of a frequency within a second passband different from the first passband, and a capacitor that has a first end and a second end and connects the first filter and the second filter.

A multilayer circuit board with an LC resonant circuit that has an electronic component package including the multilayer circuit board with the LC resonant circuit are provided. The multilayer circuit board with the LC resonant circuit configured by alternately laminating conductive layers and insulating resin layers on both sides of a core substrate includes a first set of wiring lines, a set of vias, and a second set of wiring lines. The first set of wiring lines configures both ends of the LC resonant circuit and is formed in a first one of the conductive layers. The set of vias extends through the insulating resin layers. The second set of wiring lines is connected to an input/output terminal of the LC resonant circuit and is formed in a second one of the conductive layers. The first set of wiring lines is connected to the second set of wiring lines.

A multiplexer includes: a first terminal; a second terminal; a third terminal; a first filter connected between the first and second terminals, including a first capacitor, a first inductor, and one or more first acoustic wave resonators, and having a first passband; a second filter connected between the first and third terminals, including a second capacitor, a second inductor, and one or more second acoustic wave resonators, and having a second passband higher than the first passband; a substrate having a surface on which at least one first acoustic wave resonator of the one or more first acoustic wave resonators and at least one second acoustic wave resonator of the one or more second acoustic wave resonators are located; and a metal structure located on the surface and located between the at least one first acoustic wave resonator and the at least one second acoustic wave resonator.

A filter circuit module includes a filter circuit element, a circuit board with the filter circuit element mounted thereon, and a first inductor. The filter circuit element includes a resonant circuit capacitor defining a portion of an LC parallel resonant circuit, and a phase-shift circuit. The circuit board includes a second inductor. A primary coil and a secondary coil of the phase-shift circuit are overlapped with the second inductor, viewed in a direction of a winding axis. The resonant circuit capacitor is closer to a mounting surface on which the filter circuit element is mounted on the circuit board, compared with the primary coil and the secondary coil. The resonant circuit capacitor includes a capacitor electrode covering a coil opening of the primary coil and a coil opening of the secondary coil, viewed in the direction of the winding axis.

Examples provide a wideband filter structure and apparatus, a radio transceiver, a mobile terminal, and a method for filtering a radio signal. The wideband filter structure (10) for a radio signal comprises a combination of at least one acoustic resonator (12) and at least one analog resonator (14). The acoustic resonator (12) is coupled to the analog resonator (14). The wideband filter structure (10) comprises a further component (16), which is coupled to the combination of the acoustic resonator (12) and the analog resonator (14).

Radio frequency (RF) systems with tunable filters are provided herein. In certain embodiments, an RF system includes a first RF processing circuit configured to process a first frequency band of a first communication standard and a second frequency band of a second communication standard. The first frequency band and the second frequency band are close in frequency and/or partially overlapping in frequency. The first RF processing circuit includes a tunable filter for changing the bandwidth of the first RF processing circuit to enhance the robustness of the first RF processing circuit to blocker or jammer signals of a third frequency band.

An apparatus includes a transceiver circuit, a series capacitor, and a shunt switch. The transceiver circuit may comprise a transmit chain including an output matching network and a receive chain including an input matching network. An output of the output matching network may be connected directly to an input/output of the transceiver circuit. The series capacitor may be connected between an input of the input matching network and the output of the output matching network. The shunt switch may be connected between the input of the input matching network and a circuit ground potential of the transceiver circuit.

A noise suppressor includes a first differential-mode transmission module, a second differential-mode transmission module and a common-mode absorption module. The first and second differential-mode transmission modules are configured to receive a differential signal at one of the first and second differential-mode transmission modules, and output the differential signal at the other of the same. The common-mode absorption module is electrically connected to a reference node, and is configured to absorb common-mode noise of the differential signal from at least one of the first differential-mode transmission module or the second differential-mode transmission module.

An LC resonator includes a laminate body including dielectric layers that are laminated in a lamination direction. The LC resonator includes a first capacitor, a second capacitor, and an inductor connected between the first capacitor and the second capacitor. A first end of the inductor is isolated in a direct current from a ground node by the first capacitor. A second end of the inductor is isolated in a direct current from the ground node by the second capacitor.