Bragg Mirror BAW Resonator Tuning Without Q-Factor Loss
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Solution Overview
Problem
Frequency tuning of bulk-acoustic wave (BAW) resonators is difficult to achieve without compromising the quality factor and increasing power consumption, which is a challenge in scaling down quartz crystal oscillators for modern electronic systems.
Innovation Solution
A tunable BAW resonator design incorporating a Bragg mirror with a metal layer and dielectric layer, coupled with an RF signal source and amplifier circuit, allows for adjustment of the parallel resonance frequency and quality factor by modifying the RF signal applied to the metal layer, enabling precise frequency tuning without reducing the quality factor or increasing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a capacitor is added across the BAW resonator to enable frequency tuning, then frequency tuning capability is improved, but quality factor decreases and power consumption increases
Solution Approach 1:
The patent introduces a Bragg mirror as an intermediary structure between the BAW resonator and the tuning capacitor. The Bragg mirror, consisting of alternating high and low impedance layers, acts as an acoustic reflector that isolates the resonator from the capacitive loading effect. This allows frequency tuning to be achieved through the interaction between the RF signal applied to the Bragg mirror and the resonator, rather than directly coupling a capacitor across the resonator terminals, thereby maintaining high quality factor while enabling tuning capability
Solution Approach 2:
The patent utilizes parameter changes in the Bragg mirror structure to achieve frequency tuning. By applying an RF signal to the Bragg mirror and adjusting the signal parameters (frequency, amplitude), the acoustic impedance of the Bragg mirror changes, which in turn modifies the resonant frequency of the BAW resonator. This parameter-based tuning approach avoids the need for direct capacitive coupling and maintains the resonator's quality factor
2Adaptability or versatility
If a capacitor is added across the BAW resonator to enable frequency tuning, then frequency tuning capability is improved, but power consumption increases
Solution Approach 1:
The Bragg mirror serves as an intermediary that enables frequency tuning through acoustic wave interaction rather than direct electrical capacitive coupling. The RF signal applied to the Bragg mirror modulates the acoustic impedance, which tunes the resonator frequency. This indirect tuning mechanism through the Bragg mirror intermediary reduces the power consumption compared to direct capacitive coupling methods
Solution Approach 2:
The patent replaces the electrical capacitive tuning mechanism with an acoustic-based tuning mechanism using the Bragg mirror. Instead of using electrical capacitors that consume power through continuous charging and discharging, the system uses acoustic wave propagation and reflection in the Bragg mirror layers to achieve frequency tuning, thereby reducing power consumption
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design allows for precise frequency tuning of BAW resonators, improving their scalability and performance in modern electronic systems while maintaining high quality factor and reducing power consumption.
Implementation Method 1
BAW resonators use a piezoelectric effect to convert electrical energy into mechanical energy resulting from an applied RF voltage and vice versa
Implementation Method 2
A Bragg mirror is formed by a number of alternating high and low impedance layers
Implementation Method 3
an amplifier circuit between the Bragg mirror metal layer and either the first electrode or the second electrode
Data Source
AI summary
A tunable bulk acoustic wave (BAW) resonator includes: a first electrode adapted to be coupled to an oscillator circuit; a second electrode adapted to be coupled to the oscillator circuit; and a piezoelectric layer between the first electrode and the second electrode; and a Bragg mirror. The Bragg mirror has: a metal layer; and a dielectric layer between the metal layer and either of the first electrode or the second electrode. The tunable BAW resonator also includes: a radio-frequency (RF) signal source having a first end and a second end, the first end coupled to the first electrode, and the second end coupled to the second electrode; and an amplifier circuit between either the first electrode or the second electrode and the Bragg mirror metal layer.