A filter circuit comprises a main operating unit (MU) arranged in the series signal line providing most of the filter function of the filter circuit. A micro acoustic last series resonator (RL.sub.s) as a last element of the main operating unit in the series signal line is prone to excite a spurious mode that is damped with a final series capacitance (CE.sub.s) circuited between the last element and the antenna terminal (AT).

A multiplexer includes a common terminal, reception output terminals (120 and 130), a filter (20) that is connected between the common terminal and the reception output terminal (120), a filter (30) that is connected between the common terminal and the reception output terminal (130) and has a pass band different from a pass band of the filter (20), and an impedance matching circuit that is arranged between the common terminal and the filter (30). The impedance matching circuit includes a parallel-arm resonator that is connected between a node (N1) on a path connecting the common terminal to the filter (30) and a ground.

RF filtering circuitry comprises a first node, a second node, and a series signal path between the first node and the second node. A number of acoustic resonators are coupled to one or more of the first node and the second node via the series signal path. A first one of the acoustic resonators is associated with a first quality factor and a first electromechanical coupling coefficient. A second one of the acoustic resonators is associated with a second quality factor and a second electromechanical coupling coefficient. The first quality factor is different from the second quality factor and the first electromechanical coupling coefficient is different from the second electromechanical coupling coefficient.

An RF diplexer circuit device using modified lattice, lattice, and ladder circuit topologies. The diplexer can include a pair of filter circuits, each with a plurality of series resonator devices and shunt resonator devices. In the ladder topology, the series resonator devices are connected in series while shunt resonator devices are coupled in parallel to the nodes between the resonator devices. In the lattice topology, a top and a bottom serial configurations each includes a plurality of series resonator devices, and 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. A multiplexing device or inductor device can be configured to select between the signals coming through the first and second filter circuits.

An acoustic wave filter includes: a series-arm resonator disposed on a path that connects input/output terminals; and a parallel-arm circuit connected to a node on the path and a ground. The parallel-arm circuit includes a parallel-arm resonator and a capacitor connected in parallel to each other. The capacitor includes a comb-shaped electrode that includes electrode fingers. A frequency at which impedance of the capacitor has a local maximum value is located outside a passband of the acoustic wave filter. The comb-shaped electrode has at least two different electrode finger pitches or at least two different electrode finger duty ratios.

In an array of single crystal acoustic resonators, the effective coupling coefficient of first and second strained single crystal filters are individually tailored in order to achieve desired frequency responses. In a duplexer embodiment, the effective coupling coefficient of a transmit band-pass filter is lower than the effective coupling coefficient of a receive band-pass filter of the same duplexer. The coefficients can be tailored by varying the ratio of the thickness of a piezoelectric layer to the total thickness of electrode layers or by forming a capacitor in parallel with an acoustic resonator within the filter for which the effective coupling coefficient is to be degraded. Further, a strained piezoelectric layer can be formed overlying a nucleation layer characterized by initial surface etching and piezoelectric layer deposition parameters being configured to modulate a strain condition in the strained piezoelectric layer to adjust piezoelectric properties for improved performance in specific applications.

Multiplexing circuits with bulk acoustic wave (BAW) resonators as network elements for higher performance are provided. Multiplexing networks which support newer fourth generation (4G) and fifth generation (5G) standards may include a combination of multiplexers having a number of radio frequency (RF) filters connected to an antenna at the same time. One critical aspect of such a multiplexer design is the loading of these filters to each other, in which the static capacitance presented by a filter can be beneficial or detrimental to other filters in the multiplexing network. Aspects of the present disclosure introduce a BAW resonator to improve multiplexing network performance using the frequency-dependent capacitance, resonance, and/or anti-resonance of the BAW resonator.

The invention provides a filter device, an RF front-end device and a wireless communication device. The filter device comprises a substrate, at least one resonance device, a passive device and a connector, wherein the at least one resonance device has a first side and a second side opposite to the first side, the substrate is located on the first side, and the passive device is located on the second side. The at least one resonance device is connected to the passive device through the connector. The RF filter device formed by integrating the resonance device (such as an SAW resonance device or a BAW resonance device) and the passive device (such as an IPD) in one die can broaden the passband width, has a high out-of-band rejection, and occupies less space in an RF front-end chip.

A radio frequency module includes a mount board, an acoustic wave filter, a temperature sensor, and a correction circuit. The mount board has a first principal surface and a second principal surface on opposite sides of the mount board. The acoustic wave filter is disposed on the first principal surface side of the mount board. The temperature sensor is disposed on the second principal surface side of the mount board. The correction circuit corrects a pass band of the acoustic wave filter in accordance with a temperature measured by the temperature sensor.

Embodiments of the invention include an acoustic wave resonator (AWR) module. In an embodiment, the AWR module may include a first AWR substrate and a second AWR substrate affixed to the first AWR substrate. In an embodiment, the first AWR substrate and the second AWR substrate define a hermetically sealed cavity. A first AWR device may be positioned in the cavity and formed on the first AWR substrate, and a second AWR device may be positioned in the cavity and formed on the second AWR substrate. In an embodiment, a center frequency of the first AWR device is different than a center frequency of the second AWR device. In additional embodiment of the invention, the AWR module may be integrated into a hybrid filter. The hybrid filter may include an AWR module and other RF passive devices embedded in a packaging substrate.