High-frequency Reference System Implementations Utilizing Mirror-encapsulated BAW Resonators

This paper introduces TI's mirror-encapsulated bulk acoustic wave (BAW) resonator technology and two novel system applications. Similar to other BAW resonators, the dual-Bragg acoustic resonator (DBAR) utilizes piezoelectric aluminum nitride (AIN) thin film between two metal electrodes. However, the DBAR operation requires no cavity on either side of the resonant body. This unique micro-acoustic resonator technology enables cost-effective system integration in mass production. The first system application is a novel network synchronizer based on an integrated ultra-low noise voltage-controlled BAW oscillator (VCBO). When operating as a jitter cleaner, the synthesized output clock rms jitter can be reduced to less than 60 fs (12 kHz–20 MHz). The second application uses this 2.5 GHz DBAR-oscillator as a high-frequency reference clock, achieving a ±30 ppm Bluetooth Low Energy (BLE) compliant crystal-less radio.