Disclosed is a filter bank module having a substrate, an antenna port terminal, and a filter bank die. The filter bank die is fixed to the substrate and includes a first acoustic wave (AW) filter having a first antenna terminal coupled to the antenna port terminal and a first filter terminal, wherein the first AW filter is configured to pass a first passband and attenuate frequencies outside the first passband, and a second AW filter having a second filter terminal, and a second antenna terminal coupled to the first antenna terminal to effectively diplex signals that pass through the first AW filter and the second AW filter, wherein the second AW filter is configured to pass a second passband that is spaced from the first passband to minimize interference between first bandpass and the second bandpass while attenuating frequencies outside the second passband.

Disclosed is a filter bank die having a first acoustic wave (AW) filter having a first antenna terminal and a first filter terminal, and a second AW filter having a second filter terminal, and a second antenna terminal coupled to the first antenna terminal to effectively diplex signals that pass through the first AW filter and the second AW filter.

An acoustic wave filter includes a first signal terminal, an antenna terminal, a ladder-type filter connected between the first signal terminal and the antenna terminal and including one or more serial resonators and one or more parallel resonators connected in a ladder shape, and a capacitor part and an inductor part which are connected in series between the first signal terminal and a reference potential.

A multiplexer includes a transmission filter and a reception filter connected to a common terminal, a first inductor connected to the common terminal, and a multilayer substrate on which the transmission filter and the reception filter are mounted and which includes dielectric layers. The transmission filter includes a parallel-arm resonator connected to a path between the common terminal and a transmission terminal and a parallel-arm terminal, and a second inductor connected to the parallel-arm terminal and ground. The first inductor includes a first coil pattern on a first dielectric layer and a second coil pattern on a second dielectric layer. The second inductor includes a third coil pattern on the first dielectric layer and that is magnetically coupled to the first coil pattern. The inductance value of the second coil pattern is greater than that of the first coil pattern.

A transmission filter is arranged in a first filter region and has one or more acoustic wave resonators, a plurality of terminal electrodes, and a plurality of wires. A reception filter is arranged in a second filter region and has one or more acoustic wave resonators, a plurality of terminal electrodes, and a plurality of wires. The first filter region and the second filter region are arranged adjacently to each other and have at least sides constituting a pair and opposing to each other. At least either one of the first filter region and the second filter region has no wire extending along one side in a forbidden region that is defined by a width including a terminal electrode nearest to the one side, along the one side and over the one side opposing to the other filter region.

A transmit filter circuit includes an input terminal, an output terminal, plural series arm resonators, and a parallel arm resonator. The input terminal receives a transmit signal. The output terminal is electrically connected to an antenna. The plural series arm resonators are electrically connected in series with each other on a line between the input and output terminals. The plural series arm resonators include first and second series arm resonators. The first series arm resonator is closest to the output terminal. The second series arm resonator is second closest to the output terminal. A first end of the parallel arm resonator is electrically connected to a node between the first and second series arm resonators. A reference potential is provided to a second end of the parallel arm resonator. The resonant frequency of the first series arm resonator is higher than that of the second series arm resonator.

Aspects of this disclosure relate to a multiplexer that includes a switchable acoustic wave filter. The switchable acoustic wave filter can include one or more acoustic wave resonators, switchable acoustic wave resonators, and a switch configurable into at least a first state and a second state. The switch can select a different subset of the switchable acoustic wave resonators to filter a radio frequency signal together with at least the one or more acoustic wave resonators in the first state than in the second state. Related filters, radio frequency systems, wireless communication devices, and methods are also disclosed.

A SAW resonator comprises two reflectors and a transducer arranged between the reflectors. A resonant space between the transducer and a respective reflector is set large enough to enable occurrence of main resonance and at least one further resonance of comparable admittance. Thus, a multiple resonant resonator is achieved that can be used as a parallel resonator in a filter circuit with a DMS track for example to improve attenuation in a stop band.

When a current flowing in a series circuit including an equivalent resistance, an equivalent inductor, and an equivalent capacitance in an electric equivalent circuit of a specific resonator in each filter is defined as an acoustic path current, under conditions that a phase of an acoustic path current of a first transmission filter at a side of a common terminal at a frequency within a first transmission band is represented as θ1.sub.Tx, a phase of an acoustic path current of the first transmission filter at the side of the common terminal at a frequency within a second transmission band is represented as θ2.sub.Tx, a phase of an acoustic path current of a first reception filter at the side of the common terminal at a frequency within the first transmission band is represented as θ1.sub.Rx, and a phase of an acoustic path current of the first reception filter at the side of the common terminal at a frequency within the second transmission band is represented as θ2.sub.Rx, a multiplexer satisfies a first condition: |(2.Math.θ1.sub.Tx−θ2.sub.Tx)−(2.Math.θ1.sub.Rx−θ2.sub.Rx)|=180°±90°, or a second condition: |(2.Math.θ2.sub.Tx−θ1.sub.Tx)−(2.Math.θ2.sub.Rx−θ1.sub.Rx)|=180°±90°.

A high-isolation and anti-glue-invasion Surface Acoustic Wave (SAW) duplexer includes a transmitting filter and a receiving filter. The isolation of the duplexer is improved by adjusting the positions of parallel resonance arms of the receiving filter and optimizing the distances between a grounding metal wiring of a Double Mode Structure (DMS) filter in the receiving filter and other grounding metal wirings and a distance between the grounding metal wiring of the DMS filter in the receiving filter and a signal metal wiring, and the grounding metal wiring is further arranged to surround the series resonance arms and the parallel resonance arms, so as to fill blank positions between the resonance arms and the edge of a package.