The present disclosure relates to a Bulk Acoustic Wave (BAW) resonator with tunable electromechanical coupling. The disclosed BAW resonator includes a bottom electrode, a top electrode, and a multilayer transduction structure sandwiched therebetween. Herein, the multilayer transduction structure is composed of multiple transduction layers, and at least one of the transduction layers is formed of a ferroelectric material, whose polarization will vary with an electric field across the ferroelectric material. Upon adjusting direct current (DC) bias voltage across the bottom electrode and the top electrode, an overall polarization of the multilayer transduction structure and an overall electromechanical coupling coefficient of the multilayer transduction structure are capable of being changed. Once the change of the overall electromechanical coupling coefficient of the multilayer transduction structure is completed, the overall electromechanical coupling coefficient of the multilayer transduction structure will remain unchanged after removing the DC bias voltage.

The present disclosure relates to a Bulk Acoustic Wave (BAW) resonator, which includes a bottom electrode, a top electrode structure, and a ferroelectric layer sandwiched in between. Herein, the ferroelectric layer is formed of a ferroelectric material, which has a box-shape polarization-electric field (P-E) curve. The ferroelectric layer includes a ferroelectric border (BO) portion positioned at a periphery of the ferroelectric layer and a ferroelectric central portion surrounded by the ferroelectric BO portion. The ferroelectric BO portion has a first polarization and a first electromechanical coupling coefficient, and the ferroelectric central portion has a second polarization and a second electromechanical coupling coefficient. An absolute value of the first polarization is less than an absolute value of the second polarization, and the first electromechanical coupling coefficient is less than the second electromechanical coupling coefficient. The ferroelectric central portion is configured to provide a resonance of the BAW resonator.

The present disclosure relates to a Bulk Acoustic Wave (BAW) resonator, which includes a bottom electrode, a top electrode structure, and a multilayer transduction structure sandwiched therebetween. Herein, the multilayer transduction structure is composed of multiple transduction layers, at least one of which is formed of a ferroelectric material with a box-shape polarization-electric field curve. Each transduction layer includes a transduction border (BO) portion positioned at a periphery of a corresponding transduction layer and a transduction central portion surrounded by the transduction BO portion. A combination of all transduction BO portions forms a transduction BO section of the multilayer transduction structure, and a combination of all transduction central portions forms a transduction central section of the multilayer transduction structure. An electromechanical coupling coefficient of the transduction BO section is less than an electromechanical coupling coefficient of the transduction central section.

A voltage sensor device includes an oscillator unit, the oscillator unit having a tunable bulk acoustic wave (BAW) resonator device and an oscillator core. The voltage sensor device also includes a frequency analyzer configured to obtain frequency measurements for the oscillator unit and to determine a voltage sense value based on a comparison of at least some of the obtained frequency measurements. The voltage sensor device also includes an output interface configured to store or output voltage sense values determined by the frequency analyzer.

Examples of increasing yield and operating temperature range of transmitters are disclosed. In one example, a transmitter has an a thin-film bulk acoustic (FBAR) resonator. The transmitter may be a Bluetooth Low Energy (BLE) transmitter. In this example, the FBAR-based BLE transmitter does not require or have a phase locked loop, and does not require or have a crystal reference. The FBAR-based BLE transmitter may have an oscillator with a split capacitor array. The oscillator may be a Pierce oscillator with a split capacitor array. The FBAR-based transmitter and calibration methods described herein provide a greater yield and wider operating range than prior transmitters.

A digitally tunable acoustic wave resonator includes, in part, a first electrode positioned above a substrate, a composite stack positioned above the first electrode, and a second electrode positioned above the composite stack. The composite stack may include one or more alternate layers of a ferroelectric layer and a transition-metal nitride layer. The transition-metal nitride layer can be positioned above the ferroelectric layer, except the ferroelectric layer at the top of the composite stack. The ferroelectric layer comprises an aluminum scandium nitride layer Al.sub.1-xSc.sub.xN, where 0<x<1.

The present disclosure relates to a tunable Bulk Acoustic Wave (BAW) resonator with a top electrode, a bottom electrode, a piezoelectric layer sandwiched between the top electrode and the bottom electrode, and a reflection region underneath the bottom electrode. The reflection region includes a reflection layer and an ion-conductible structure between the bottom electrode and the reflection layer. Herein, the ion-conductible structure has a first terminal layer coupled to the bottom electrode, a second terminal layer coupled to the reflection layer, and an ion conductor between the first terminal layer and the second terminal layer. The ion conductor is eligible to transport ions between the first terminal layer and the second terminal layer, so as to achieve a mass-loading shift between the first terminal layer and the second terminal layer, and consequently, to tune a resonance frequency of the tunable BAW resonator.

A digitally tunable acoustic wave resonator includes, in part, a first electrode positioned above a substrate, a composite stack positioned above the first electrode, and a second electrode positioned above the composite stack. The composite stack may include one or more alternate layers of a ferroelectric layer and a transition-metal nitride layer. The transition-metal nitride layer can be positioned above the ferroelectric layer, except the ferroelectric layer at the top of the composite stack. The ferroelectric layer comprises an aluminum scandium nitride layer Al.sub.1-xSc.sub.xN, where 0<x<1.

A system includes a tunable bulk acoustic wave (BAW) resonator device and a direct-current (DC) tuning controller coupled to the tunable BAW resonator device. The system also includes an oscillator circuit coupled to the tunable BAW resonator device. The DC tuning controller selectively adjusts a DC tuning signal applied to the tunable BAW resonator device to adjust a signal frequency generated by the oscillator circuit.

The present invention provides tunable film bulk acoustic resonators (FBARs) with the resonant frequency of the acoustic wave to be excited and to be transmitted tuned by digital to analog converters which convert an input digital signal to an output DC voltage and provide DC bias voltages to the FBARs through integrated thin film biasing resistors. The polarity and the value of the output DC voltage are controlled by the input digital signal to achieve selection and tuning of the resonant frequency of the FBARs. A plurality of the tunable FBARs are connected to form microwave filters with tunable bandpass frequencies and oscillators with selectable resonating frequencies by varying the input digital signals applied to the digital to analog converters.