Double-port AlN/Sapphire High overtone Bulk Acoustic Resonators for the stabilization of radio-frequency Oscillators

The interest of double-port AlN/Sapphire high overtone bulk acoustic resonators for the stabilization of radio-frequency oscillators is investigated. Resonators are built by depositing AlN onto Sapphire to provide high quality factors, as required for stable oscillators. The resonators are based on laterally-coupled single resonators exchanging energy via a gap of few tens of mu m separating them and adjusted to optimize the quality factor. Combining AlN with high acoustic quality materials finally has provided a quality factor of 53,000 at 1.8 GHz (Q.f product of about 9.5 x 10(13)) at room temperature. An oscillator stabilized with this resonator has been characterized, yielding a phase noise floor of -155 dBc/Hz and an Allan deviation of 10(9) for tau = 1 s.