Filter circuits having a resonator-based filter and a magnetically-coupled filter are disclosed. A filter circuit is deployed with a resonator-based passband filter connected to a magnetically-coupled filter which mitigates or reduces flyback of the resonator-based filter. The magnetically-coupled filter can be a passband filter with a relatively low insertion loss. The magnetically-coupled filter can be designed to mitigate flyback of the resonator-based filter by attenuating frequency response at selected frequency ranges.

Acoustic resonators, such as bulk acoustic wave (BAW) resonators, are disclosed that include phase shift structures. Acoustic resonators, including stacked crystal filters (SCFs) and coupled resonator filters (CRFs), may include inverted piezoelectric layers that are configured to provide built-in phase shift capabilities. Circuit topologies that include such SCFs may be provided with simplified structures and reduced loss. Circuit topologies with such CRFs may be provided with more symmetrical electrical connections and improved phase balance over operating frequencies. SCFs with phase shift structures may additionally include spurious mode suppression by modifying piezoelectric coupling profiles within one or more layers. Mode suppression configurations may include structures with one or more inverted polarity piezoelectric layers, one or more non-piezoelectric layers, one or more thicker electrodes of the SCF, and combinations thereof.

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.

An acoustic waveguide having high-Q resonator characteristics is disclosed and a fabrication method is described. Various waveguide-based test-vehicles, implemented in single crystal silicon and transduced by thin aluminum nitride films, are demonstrated. Silicon resonators with type-I and type-II dispersion characteristics are presented to experimentally justify the analytical mode synthesis technique for realization of high quality-factor silicon Lamb wave resonators. An analytical design procedure is also presented for geometrical engineering of the waveguides to realize high-Q resonators without the need for geometrical suspension through narrow tethers or rigid anchors. The effectiveness of the dispersion engineering methodology is verified through development of experimental test-vehicles in 20 m-thick single-crystal silicon (SCS) waveguides with 500 nm aluminum nitride transducers.

A compensation circuit reduces the negative effects of antenna-to-antenna coupling between proximately located antennas. The compensation circuit is coupled between first and second antenna ports. A first transmit/receive path extends from radio frequency (RF) circuitry to the first antenna port. A second transmit/receive path extends from the RF circuitry to the second antenna port. Antennas are coupled to each of the antenna ports. The compensation circuit includes negatively coupled first and second inductors, which are coupled in series between the first antenna port and the second antenna port. At least one shunt acoustic resonator is coupled between a fixed voltage node and a common node between the first and second inductors. In operation, the compensation circuit presents a negative capacitance between the first antenna port and the second antenna port over the first frequency range to reduce the effects of the antenna-antenna coupling.

A filter may include a plurality of bulk acoustic wave resonators including one or more series resonators and one or more shunt resonators formed by a first electrode, a piezoelectric layer, and a second electrode sequentially stacked on a substrate, a cap accommodating the plurality of bulk acoustic wave resonators therein, and one or more switches provided on the cap.

A bulk acoustic wave resonator includes a substrate, a lower electrode connection member, a lower electrode, a piezoelectric layer, an upper electrode, an upper electrode connection member, and a dielectric layer in which the lower electrode, the piezoelectric layer, and the upper electrode are embedded. The lower electrode, the piezoelectric layer, and the upper electrode constitute a resonant portion. An extension portion extends away from either the lower electrode or the upper electrode to protrude outwardly from the resonant portion. A capacitor portion is constituted by the extension portion, a portion of the upper electrode connection member disposed above the extension portion, and a portion of the dielectric layer disposed between the extension portion and the portion of the upper electrode connection member disposed above the extension portion.

A filter includes: series resonators connected to each other in series; shunt resonators connected to first nodes between some of the series resonators; and a variable capacitor connected to a second node between some of the series resonators, and forming a pole configured to suppress harmonics.

A coupled resonator filter includes a first resonator, a second resonator, one or more intervening layers, a first border ring, and a second border ring. The first resonator includes a first piezoelectric layer and a first electrode in contact with the first piezoelectric layer. The second resonator includes a second piezoelectric layer and a second electrode in contact with the second piezoelectric layer. The one or more intervening layers are between the first resonator and the second resonator and acoustically couple the first resonator and the second resonator. The first border ring is on the first electrode. The second border ring is on the second electrode. By providing both the first border ring and the second border ring, spurious modes in the coupled resonator filter may be suppressed, thereby improving the performance thereof.

An RF triplexer 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.