A filter, a radio frequency device and an electronic apparatus. The filter includes a series branch, N parallel branches and a bridged branch; the series branch includes M series resonators; each of the N parallel branches includes a parallel resonator; the bridged branch includes a bridged resonator and a first inductor, the first end of each of the parallel branches is grounded, the second end of each of the parallel branches is connected with the series branch, the third end is located at a side of the bridged resonator away from the first inductor, the fourth end is located at a side of the first inductor away from the bridged resonator, the third end is connected to the first end of the ith parallel branch, the fourth end is connected to the second end of the (i+k)th parallel branch.

The present disclosure provides a bandpass filter circuit. An example band pass filter circuit comprises, in series, a first high-pass filter, a bandpass filter, and a second high-pass filter. The bandpass filter comprises: first and second acoustic resonators serially disposed between first and second nodes; two first coils disposed in series with each other, and disposed in parallel to the first acoustic resonator; two second coils disposed in series with each other, and disposed in parallel to the second acoustic resonator; a third acoustic resonator disposed between a third mid-node between the first coils and a fourth node; and a fourth acoustic resonator disposed between a fifth mid-node between the second coils and the fourth node.

An RF circuit device using modified lattice, lattice, and ladder circuit topologies. The devices can include four resonator devices and four shunt resonator devices. In the ladder topology, the resonator devices are connected in series from an input port to an output port while shunt resonator devices are coupled the nodes between the resonator devices. In the lattice topology, a top and a bottom serial configurations each includes a pair of resonator devices that are coupled to differential input and output ports. A pair of shunt resonators is cross-coupled between each pair of a top serial configuration resonator and a bottom serial configuration resonator. The modified lattice topology adds baluns or inductor devices between top and bottom nodes of the top and bottom serial configurations of the lattice configuration. These topologies may be applied using single crystal or polycrystalline bulk acoustic wave (BAW) resonators.

A Lamb wave filter is provided which has improved out of band rejection, the filter including a substrate having a center region and two edge regions, a first set of electrodes arranged as a first interdigital transducer displaced on one of the two edge regions and configured to receive an input signal, a second set of electrodes arranged as a second interdigital transducer displaced on the other of the two edge regions and configured to provide a filtered output signal, and a third set of electrodes disposed parallel to the first and second sets of electrodes on the center region of the substrate.

A filter, a radio frequency device and an electronic apparatus. The filter includes a series branch, N parallel branches and a bridged branch; the series branch includes M series resonators; the bridged branch includes a bridged resonator and a first inductor, the first end of the parallel branch is grounded, the second end of the parallel branch is connected with the series branch, the bridged branch includes a third end and a fourth end, the third end is located at a side of the bridged resonator away from the first inductor, the fourth end is located at a side of the first inductor away from the bridged resonator, the third end is connected to the first end of the ith parallel branch, the fourth end is connected to the second end of the (i+k)th parallel branch, a value of k is 2, values of M and N are equal.

According to the present disclosure, an acoustic wave filter is provided. The acoustic wave filter has a pass band and is configured to filter a radio frequency signal. The acoustic wave filter comprises a series resonator and a shunt resonator, the shunt resonator having a primary mode defined by a resonant frequency of the shunt resonator and a secondary mode defined by a longitudinal mode of the shunt resonator, the primary mode defining a lower edge of the pass band and the secondary mode being of a higher frequency than the primary mode. A corresponding radio-frequency module and wireless mobile device comprising said acoustic wave filter are also provided.

A piezoelectric device includes a piezoelectric layer including a thickness in a first direction, and upper and lower surfaces, a support on a side of the lower surface of the piezoelectric layer, an upper electrode on the upper surface of the piezoelectric layer, a lower electrode on the lower surface of the piezoelectric layer with at least a portion of the lower electrode facing the upper electrode, and a reinforcement film on at least one of the upper and lower surfaces of the piezoelectric layer. The support includes a space portion in a region overlapping with at least a portion of the upper and lower electrodes. In plan view seen in the first direction, the reinforcement film overlaps with at least a portion of a border between a region overlapping with the space portion and a region not overlapping with the space portion.