In a multilayer filter, first and second resonant circuits are arranged in a direction crossing a stacking direction of a plurality of dielectric layers. An input/output portion includes an input/output port group including an unbalanced port and a pair of balanced ports or an input/output port group including two pairs of balanced ports. The second resonant circuit includes an inductor conductor, a first capacitor conductor, and a second capacitor conductor. The inductor conductor includes first and second ends. The first capacitor conductor is connected to the first end. The second capacitor conductor is connected to the second end. The second dielectric layer has a dielectric constant lower than that of the first dielectric layer. The first and second capacitor conductors are provided in the first dielectric layer. At least a part of the inductor conductor is provided in the second dielectric layer.

A coupled resonator filter including a first parallel resonator including a first capacitance connected in parallel with a first inductance. The filter includes a second parallel resonator including a second capacitance connected in parallel with a second inductance and a third parallel resonator including a third capacitance connected in parallel with a third inductance. Magnetic coupling between the first inductance and the second inductance, between the second inductance and the third inductance, and between the first inductance the third inductance occurs in accordance with first, second and third coupling factors, respectively. A frequency response of the coupled resonator filter includes a notch when values of the first coupling factor, the second coupling factor and the third coupling factor satisfy predetermined conditions.

Aspects of this disclosure relate to a band pass filter that includes LC resonant circuits coupled to each other by a capacitor. A bridge capacitor can be in parallel with series capacitors, in which the series capacitors include the capacitor coupled between the LC resonant circuits. The bridge capacitor can create a transmission zero at a frequency below the passband of the band pass filter. The LC resonant circuits can each include a surface mount capacitor and a conductive trace of the substrate, and an integrated passive device die can include the capacitor. Band pass filters disclosed herein can be relatively compact, provide relatively good out-of-band rejection, and relatively low loss.

Certain aspects of the present disclosure provide a filter circuit and techniques for filtering using the filter circuit. The filter circuit generally includes a first filter stage having a first acoustic wave resonator coupled in a series path between a first port of the filter circuit and a second port of the filter circuit, a first inductor-capacitor (LC) tank circuit, a first capacitor coupled between a first terminal of the first acoustic wave resonator and the first LC tank circuit, the first LC tank circuit being coupled between the first capacitor and a reference potential node, and a second capacitor coupled between a second terminal of the first acoustic wave resonator and the first LC tank circuit. In some aspects, the filter circuit includes one or more other filter stages coupled to the first filter stage.

In a multilayer filter, first to fourth resonant circuits are connected to an input/output portion. The input/output portion includes an input/output port group including an unbalanced port and a pair of balanced ports or an input/output port group including two pairs of balanced ports. Each of the first to fourth resonant circuits includes an inductor conductor and first and second capacitor conductors. The inductor conductor includes first and second ends. The first capacitor conductor is connected to the first end. The second capacitor conductor is connected to the second end. The second and third resonant circuits are magnetically coupled to each other. The second and third resonant circuits are arranged between the first resonant circuit and the fourth resonant circuit in a first direction. Each of first and second electrodes of a jump capacitor conductor is connected to the inductor conductors of the first and fourth resonant circuits.

A filter device includes a multilayer body including dielectric layers, an input terminal, an output terminal, a ground terminal, a common electrode, a ground electrode, resonators, a shield electrode, and ground vias. A first ground via couples the shield electrode and the ground electrode via the common electrode. A second ground via directly couples the shield electrode and the ground electrode without passing the common electrode. A first via of a first resonator has one end coupled to the common electrode and another end coupled to the input terminal. A first plate electrode is coupled to the first via and at least partially overlaps the ground electrode when viewed in plan view. A second resonator includes second vias and a second plate electrode. The second plate electrode is coupled to the second via and at least partially overlaps the ground electrode when viewed in plan view in the stacking direction.

A magnet-free non-reciprocal device realized using modulated filters. The device includes one or more filters in one or more branches, where each branch connects two ports or a port and a central node. The poles and zeros of each of the first, second and third filters are modulated in time such that degenerate modes at each pole and zero is split thereby destructively interfering at one or more output ports and adding up at another output port allowing non-reciprocal transmission, isolation and/or non-reciprocal phase shift. The device is able to realize a magnet-free full-duplex communication scheme implementing a magnet-free circulator for radio frequency cancellation or a magnet-free isolator or gyrator.

A compact band pass filter (BPF), including a first transmission line electromagnetically coupled to a second transmission line; an isolating surface positioned between the first transmission line and the second transmission line, wherein the isolating surface includes at least one aperture designed to produce a desired electromagnetic coupling between the first transmission line and the second transmission line wherein the coupling produces a passband such that certain frequencies within an input transmission signal are filtered out; and an array of vias configured to minimize signal energy loss within the BPF.

A high-frequency front end circuit includes a fixed frequency filter and an interference-wave suppression variable filter. The fixed frequency filter attenuates a high-frequency signal outside a specific frequency band. The interference-wave suppression variable filter attenuates a high-frequency signal in at least one used communication channel, among used communication channels that are used by a system and that causes an interference wave occurring in a neighbor frequency domain including a wireless communication channel.

According to one embodiment, a compact broadband radio frequency (RF) receiver circuit includes a low noise amplifier which includes a first amplifier stage, a second amplifier stage, an inter-stage network including a higher order filter network, where the inter-stage network is coupled between the first amplifier stage and the second amplifier stage, and a double resonance transformer network coupled to an output of the second amplifier stage. The RF receiver circuit includes a low pass filter and a mixer circuit coupled between the low noise amplifier and the low pass filter.