A wireless communication device and a filter are provided. The filter has an input end and an output end and includes a first energy storage element, a first series resonant circuit, a second series resonant circuit, a first parallel resonant circuit and a second parallel resonant circuit. The first and the second series resonant circuits respectively have a first capacitor and a first inductor connected in series. The first and the second parallel resonant circuits respectively have a second capacitor and a second inductor connected in parallel. The first series resonant circuit and the first parallel resonant circuit are electrically connected in cascade between a first end of the first energy storage element and a ground, and the second series resonant circuit and the second parallel resonant circuit are electrically connected in cascade between a second end of the first energy storage element and the ground.

A filter with three phases comprising for each phase an input terminal, an output terminal and a capacitor, wherein for each of the three phases the input terminal is electrically connected via a connection point to the output terminal, wherein the connection points of the three phases are electrically connected via the three capacitors in star and/or delta form, wherein the filter comprises a housing containing two coil blocks, wherein the housing comprises a first side and a second side opposite the first side, wherein the two coil blocks are arranged along a line between the first side and the second side, wherein a fan for cooling the two coil blocks is arranged on the first side of the housing, wherein the larger of the two coil blocks is arranged between the fan and the smaller of the two coil blocks.

A filter includes shunt circuits coupled between a reference node and each of an input port, an output port, a first node, and a second node. Resonant networks are coupled between the input port and the second node, and between the first node and the output port. Storage element circuits are coupled between the input port and the first node, and between the second node and the output port. The shunt circuits have an equivalent shunt circuit frequency response that partly defines a high passband frequency of the filter, the resonant networks have an equivalent resonant network frequency response that partly defines a low passband frequency of the filter, and the storage element circuits have an equivalent storage element circuit frequency response that defines a stopband frequency of the filter between the low passband frequency and the high passband frequency.

A filter device that removes a noise current generated by an inverter includes a first filter capacitor that is provided in parallel to a direct-current unit of the inverter, a first filter reactor that is provided between a high-potential side of the first filter capacitor and an overhead line that is a power supply source of direct-current power, and a series circuit unit in which a fuse serving as a circuit disconnecting unit that is disconnected when a current larger than a rated current flows therein, a second filter reactor serving as an inductance element, and a second filter capacitor serving as a capacitance element are connected in series, where one end of the series circuit unit is connected to a low-potential side of the first filter capacitor and one end of the first filter reactor is connected to the series circuit unit.

A filter circuit is provided which allows the pass band to be tuned to a desired communication signal while achieving increased attenuation in a given frequency band that lies outside the pass band. A filter circuit includes a fixed filter and a tunable filter. The fixed filter has a pass band wider than a frequency band corresponding to a predetermined communication signal and overlapping with the frequency band corresponding to the communication signal. The tunable filter has a stop band narrower than the pass band of the fixed filter and having tunable frequency. The fixed filter and the tunable filter are connected in series.

Aspects of this disclosure relate to a hybrid acoustic LC filter cascaded with a non-acoustic LC filter. The hybrid acoustic filter can filter a radio frequency signal. The hybrid acoustic LC filter can include acoustic resonators, an inductor, and a capacitor. The inductor and capacitor can be external to an acoustic resonator die. The non-acoustic LC filter includes an LC circuit. Related multiplexers, wireless communication devices, and methods are disclosed.

A high pass filter includes a first LC series resonator including a first end connected to a signal path, and a second end connected to at least one ground terminal, a second LC series resonator including a third end electrically connected to the signal path, and a fourth end connected to the at least one ground terminal, and a third capacitor between a first portion extending from a first capacitor to a first inductor and a second portion extending from a second capacitor to a second inductor.

In one aspect, the present disclosure provides a surface-mounted low-pass filter, including: a mounting surface having an input terminal electrode, an output terminal electrode, and a ground terminal electrode; a parallel resonant circuit between the input terminal electrode and the output terminal electrode; and a series resonant circuit between one end of the parallel resonant circuit and the ground terminal electrode, wherein the series resonant circuit has a first capacitor and a first inductor, and wherein, when the low-pass filter is viewed from above in a direction perpendicular to the mounting surface with the mounting surface on the bottom, the first inductor of the series resonant circuit is above the first capacitor.

Integrated filter and electromagnetic coupler assemblies. In certain examples, an integrated filter and electromagnetic coupler assembly includes a filter having a capacitance and a series inductance, the series inductance being connected between an input port and an output port of the integrated filter and electromagnetic coupler assembly, and combination of the capacitance and the series inductance being selected to provide the filter with a passband and a stopband. The integrated filter and electromagnetic coupler assembly further includes a coupling element positioned physically proximate the series inductance and extending between a coupled port and an isolation port of the integrated filter and electromagnetic coupler assembly, the integrated filter and electromagnetic coupler assembly being configured to provide at the coupled port a coupled signal via inductive coupling between the series inductance and the coupling element responsive to receiving an input signal at the input port.

The present subject matter relates to systems, devices, and methods for adaptively tuning antenna elements and/or associated filter elements to support multiple frequency bands. For example, a tunable filter having an input node and an output node can be selectively tunable to define one or more pass bands associated with one or more first signal bands and one or more reject bands associated with one or more second signal bands. The tunable filter can be configured to pass signals having frequencies within the first signal bands between the input node and the output node and to block signals having frequencies within the second signal bands. Furthermore, the tunable filter can be configured to selectively tune the pass bands to have a minimum pass band insertion loss at any of a variety of frequencies, including frequencies that are greater than and less than frequencies within the reject bands.