In a filter device, first and second filter sections are connected in parallel between an input terminal and an output terminal. The first filter section is a longitudinally coupled resonator-type elastic wave filter including first and second inter-stage wiring lines with a two-stage cascading connection. The second filter section is a longitudinally coupled resonator-type elastic wave filter including third and fourth inter-stage wiring lines with a two-stage cascading connection. The phases of signals flowing in the third inter-stage wiring line and the second inter-stage wiring line are inverse. Terminal portions of an interdigital transducer electrode connected to the second inter-stage wiring line and an interdigital transducer electrode connected to the third inter-stage wiring line that are connected to a potential that is not a hot-side potential are connected by a virtual ground wiring line. A hot-side wiring portion that is adjacent to the virtual ground wiring line is disposed on an insulating film provided on the piezoelectric substrate.

A high-frequency filter including first and second signal terminals, a filter circuit having a passband and a stopband and being connected between the first signal terminal and the second signal terminal, and an additional circuit connected in parallel with the filter circuit between the first signal terminal and the second signal terminal. The filter circuit is configured to provide a first output signal responsive to receipt of an input signal. The additional circuit has an attenuation band within the stopband, and is configured to provide a second output signal responsive to receiving the input signal, the first and second output signals having phase components opposite to each other in the attenuation band.

A front-end module may include an acoustic wave filter with a first and second interdigital transducer electrode, and a low noise amplifier (LNA) that converts a differential input to a single-ended output with respect to ground. The first interdigital transducer electrode may be single-ended with a first input bus bar configured to receive an input signal and a second input bus bar connected to ground. The second interdigital transducer electrode may be differential with a first output bus bar connected to a first output terminal and a second output bus bar connected to a second output terminal. The LNA may have a differential input connected to the acoustic wave filter, a first input transistor that receives a first signal from the first output terminal of the acoustic wave filter, and a second input transistor that receives a second signal from the second output terminal of the acoustic wave filter.

An apparatus is disclosed for a lattice-type filter. In example aspects, the apparatus includes a filter circuit having a first port that is single-ended and a second port that is single-ended. The filter circuit also includes a transformer, a first resonator, a second resonator, a third resonator, and a fourth resonator. The transformer includes a first terminal, a second terminal, and a third terminal, with the third terminal coupled to the second port. The first resonator is coupled between the first port and the first terminal of the transformer. The second resonator is coupled between the first port and the second terminal of the transformer. The third resonator is coupled between the first terminal of the transformer and a ground. The fourth resonator is coupled between the second terminal of the transformer and the ground.

A method for manufacturing a wafer on which are formed resonators, each resonator including, above a semiconductor substrate, a stack of layers including, in the following order from the substrate surface: a Bragg mirror; a compensation layer made of a material having a temperature coefficient of the acoustic velocity of a sign opposite to that of all the other stack layers; and a piezoelectric resonator, the method including the successive steps of: a) depositing the compensation layer; and b) decreasing thickness inequalities of the compensation layer due to the deposition method, so that this layer has a same thickness to within better than 2%, and preferably to within better than 1%, at the level of each resonator.

A high-frequency filter including first and second signal terminals, a filter circuit having a passband and a stopband and being connected between the first signal terminal and the second signal terminal, and an additional circuit connected in parallel with the filter circuit between the first signal terminal and the second signal terminal. The filter circuit is configured to provide a first output signal responsive to receipt of an input signal. The additional circuit has an attenuation band within the stopband, and is configured to provide a second output signal responsive to receiving the input signal, the first and second output signals having phase components opposite to each other in the attenuation band.

A surface acoustic wave device including a piezoelectric layer, an interdigital transducer electrode over the piezoelectric layer, and a polymeric roof layer arranged over the piezoelectric layer and interdigital transducer electrode. The polymeric roof layer is spaced apart from the piezoelectric layer to define a cavity to accommodate the interdigital transducer electrode. The polymeric roof layer is supported along a span of the polymeric roof layer by at least one pillar. The thermal conductivity of the pillar is greater than the thermal conductivity of the polymeric roof layer. Related wafer-level packages, radio frequency modules and wireless communication devices are also provided.