Abstract: A bridge-T filter is disclosed. In one aspect, the bridge-T filter may include one or more inductors associated with acoustic resonators to assist in providing out-of-band rejection while improving fractional bandwidth of the filter. In specific aspects, the additional inductors may be placed in series or parallel to the acoustic resonators. The improved fractional bandwidth and better out-of-band rejection reduces unwanted signals and improves the user experience.

Abstract: A transformer balun for high rejection unbalanced lattice filters includes two symmetrical coils separated by a shielding element. In a further exemplary aspect, the transformer may include a conductor, which may be a third coil that operates with a capacitor to form a resonant circuit that enhances mutual coupling. Using either of the exemplary transformers provides improved performance in the passband while concurrently providing out-of-band rejection at levels exceeding seventy decibels (70 dB).

Abstract: Reversed semilattice filters with improved common mode rejection characteristics are disclosed. In one aspect, a filter may include two interior nodes coupled with an impedance that treats unwanted signals as common mode signals and provides rejection for common mode signals while passing differential signals of interest. The impedance is modified to have a resonant circuit that improves signal rejection in the stop band by lowering the effective impedance at those frequencies while leaving the pass band unaffected.

Abstract: A filter circuit includes a first inductor circuit connected in series with a second inductor circuit, and a first capacitor circuit connected in series with a second capacitor circuit. The first inductor circuit and the second inductor circuit are connected between a first input/output port and a second input/output port of the filter circuit. A third inductor circuit is connected between a reference node and a first node that is between the first inductor circuit and the second inductor circuit. A resonator circuit is connected to a second node between the first capacitor circuit and the second capacitor circuit. A fourth inductor circuit is connected between the resonator circuit and the reference node. In some embodiments, another resonator circuit is connected between the input port and the output port of the filter circuit.

Abstract: A transformer balun for high rejection unbalanced lattice filters includes two symmetrical coils separated by a shielding element. In a further exemplary aspect, the transformer may include a conductor, which may be a third coil that operates with a capacitor to form a resonant circuit that enhances mutual coupling. Using either of the exemplary transformers provides improved performance in the passband while concurrently providing out-of-band rejection at levels exceeding seventy decibels (70 dB).

Abstract: Disclosed is a Bulk Acoustic Wave (BAW) filter structure with a conductive bridge forming an electrical loop with an electrode for reduced electrical losses. In exemplary aspects disclosed herein, the BAW filter structure includes a transducer with electrodes, a piezoelectric layer between the electrodes, and at least one conductive bridge offset from at least a portion of one of the electrodes by an insulating volume. The conductive bridge forms a first electrical loop between a medial end and a distal end of the electrode. Such a configuration reduces electrical resistance, heat resistance, and/or ohmic losses for improved electrical loss of the BAW filter structure.

Abstract: Disclosed is a Bulk Acoustic Wave (BAW) filter structure with a conductive bridge forming an electrical loop with an electrode for reduced electrical losses. In exemplary aspects disclosed herein, the BAW filter structure includes a transducer with electrodes, a piezoelectric layer between the electrodes, and at least one conductive bridge offset from at least a portion of one of the electrodes by an insulating volume. The conductive bridge forms a first electrical loop between a medial end and a distal end of the electrode. Such a configuration reduces electrical resistance, heat resistance, and/or ohmic losses for improved electrical loss of the BAW filter structure.

Abstract: Disclosed is a Bulk Acoustic Wave (BAW) filter structure with a conductive bridge forming an electrical loop with an electrode for reduced electrical losses. In exemplary aspects disclosed herein, the BAW filter structure includes a transducer with electrodes, a piezoelectric layer between the electrodes, and at least one conductive bridge offset from at least a portion of one of the electrodes by an insulating volume. The conductive bridge forms a first electrical loop between a medial end and a distal end of the electrode. Such a configuration reduces electrical resistance, heat resistance, and/or ohmic losses for improved electrical loss of the BAW filter structure.

Abstract: 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.

Abstract: Acoustic resonators, such as bulk acoustic wave (BAW) resonators and, in particular, acoustic resonators including stacked crystal filters (SCFs) are disclosed. SCF structures are disclosed with increased spurious free ranges by providing various arrangements of acoustically soft materials in one or more locations that correspond with high stress regions of one or more modes. For SCFs operating in first order modes, relative amounts of acoustically soft materials within shared electrodes may be increased. One or more additional layers of acoustically soft materials may also be added to SCF structures near shared electrodes. Accordingly, SCFs may be provided with increased frequency spreads between first order modes and second order modes.

Abstract: Acoustic resonators, such as bulk acoustic wave (BAW) resonators, are disclosed that include mode suppression structures. Acoustic resonators, including stacked crystal filters (SCFs), are disclosed that include spurious mode suppression by modifying a piezoelectric coupling profile within one or more layers of an SCF. 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. Symmetric input and output electrical response for SCFs with mode suppression configurations may be exhibited by including piezoelectric materials with different electromechanical coupling values and/or by dividing stress profiles differently by configuring different thicknesses for input and output sides of SCFs.

Abstract: Acoustic resonators, such as bulk acoustic wave (BAW) resonators, are disclosed that include mode suppression structures. Acoustic resonators, including stacked crystal filters (SCFs), are disclosed that include spurious mode suppression by modifying a piezoelectric coupling profile within one or more layers of an SCF. 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. Symmetric input and output electrical response for SCFs with mode suppression configurations may be exhibited by including piezoelectric materials with different electromechanical coupling values and/or by dividing stress profiles differently by configuring different thicknesses for input and output sides of SCFs.

Abstract: 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.

Abstract: Compensation of on-die inductive parasitics in ladder filters through negative mutual inductance between ground inductors is disclosed herein. An exemplary ladder filter includes a primary arm of series resonators and two or more shunt resonator arms connecting nodes between the series resonators to ground. The resonators of the ladder filter are disposed over a semiconductor substrate, to form a circuit die. Constructed ladder filter dice may fail to achieve design filter rejection due to inductive parasitics (e.g., undesired magnetic induction between components). A first shunt arm and a second shunt arm are provided with mutual negatively coupled inductors in order to compensate for these parasitics and improve filter performance.

Abstract: Acoustic resonators, such as bulk acoustic wave (BAW) resonators and, in particular, acoustic resonators including stacked crystal filters (SCFs) are disclosed. SCF structures are disclosed with increased spurious free ranges by providing various arrangements of acoustically soft materials in one or more locations that correspond with high stress regions of one or more modes. For SCFs operating in first order modes, relative amounts of acoustically soft materials within shared electrodes may be increased. One or more additional layers of acoustically soft materials may also be added to SCF structures near shared electrodes. Accordingly, SCFs may be provided with increased frequency spreads between first order modes and second order modes.

Abstract: Compensation of on-die inductive parasitics in ladder filters through negative mutual inductance between ground inductors is disclosed herein. An exemplary ladder filter includes a primary arm of series resonators and two or more shunt resonator arms connecting nodes between the series resonators to ground. The resonators of the ladder filter are disposed over a semiconductor substrate, to form a circuit die. Constructed ladder filter dice may fail to achieve design filter rejection due to inductive parasitics (e.g., undesired magnetic induction between components). A first shunt arm and a second shunt arm are provided with mutual negatively coupled inductors in order to compensate for these parasitics and improve filter performance.

Abstract: Embodiments of the disclosure are directed to a Bulk Acoustic Wave (BAW) filter structure with internal electrostatic shielding. In exemplary aspects disclosed herein, a shielded BAW filter structure includes a substrate, a plurality of transducers over the substrate, and a planar electrostatic shield between the substrate and a top electrode of the plurality of transducers. Each of the plurality of transducers forms a portion of a BAW resonator and resides in a filter including a parasitic capacitance. The planar electrostatic shield is coupled to a ground node and interrupts an electrical field associated with the parasitic capacitance of the filter to reduce the parasitic capacitance. Accordingly, the shielded BAW filter structure reduces the influence of parasitic capacitance providing improved filtering performance compared to an unshielded BAW filter structure.

Abstract: Embodiments of the disclosure are directed to a Bulk Acoustic Wave (BAW) filter structure with internal electrostatic shielding. In exemplary aspects disclosed herein, a shielded BAW filter structure includes a substrate, a plurality of transducers over the substrate, and a planar electrostatic shield between the substrate and a top electrode of the plurality of transducers. Each of the plurality of transducers forms a portion of a BAW resonator and resides in a filter including a parasitic capacitance. The planar electrostatic shield is coupled to a ground node and interrupts an electrical field associated with the parasitic capacitance of the filter to reduce the parasitic capacitance. Accordingly, the shielded BAW filter structure reduces the influence of parasitic capacitance providing improved filtering performance compared to an unshielded BAW filter structure.

Abstract: An integrated cavity filter/antenna system includes a substrate, a cavity filter formed in or on the substrate. A first cavity resonator is in or on the substrate that is enclosed by metal walls. At least a second cavity resonator is formed in or on the substrate that is enclosed by metal walls. An inter-resonator coupling structure couples energy between the first cavity resonator and the second cavity resonator. An antenna is integrated with one of the cavity resonators so that the antenna acts as both a port of the cavity filter and as a radiating element for the filter/antenna system. A connector is coupled to one of the cavity resonators for coupling energy into the filter/antenna system.

Abstract: An integrated cavity filter/antenna system includes a substrate, a cavity filter formed in or on the substrate. A first cavity resonator is in or on the substrate that is enclosed by metal walls. At least a second cavity resonator is formed in or on the substrate that is enclosed by metal walls. An inter-resonator coupling structure couples energy between the first cavity resonator and the second cavity resonator. An antenna is integrated with one of the cavity resonators so that the antenna acts as both a port of the cavity filter and as a radiating element for the filter/antenna system. A connector is coupled to one of the cavity resonators for coupling energy into the filter/antenna system.