Series-resonant VHF micromechanical resonator reference oscillators

TLDR

The authors demonstrate series‑resonant micromechanical resonator oscillators using a single‑stage zero‑phase‑shift sustaining amplifier and planar‑processed resonators with Q in the thousands, including two 10‑MHz clamped‑clamped beams of differing widths and a 64‑µm‑diameter 60‑MHz disk that offers the highest Q and power handling. Tradeoffs between Q and power handling dominate the close‑to‑carrier and far‑from‑carrier phase noise, with the 60‑MHz disk resonator achieving –110 dBc/Hz at 1‑kHz offset and –132 dBc/Hz at far‑off, and when divided to 10 MHz it reaches –125 dBc/Hz at 1‑kHz and –147 dBc/Hz far‑off.

Abstract

Series-resonant vibrating micromechanical resonator oscillators are demonstrated using a custom-designed single-stage zero-phase-shift sustaining amplifier together with planar-processed micromechanical resonator variants with quality factors Q in the thousands that differ mainly in their power-handling capacities. The resonator variants include two 40-/spl mu/m-long 10-MHz clamped-clamped-beam (CC-beam) resonators, one of them much wider than the other so as to allow larger power-handling capacity, and a 64-/spl mu/m-diameter 60-MHz disk resonator that maximizes both Q and power handling among the resonators tested. Tradeoffs between Q and power handling are seen to be most important in setting the close-to-carrier and far-from-carrier phase noise behavior of each oscillator, although such parameters as resonant frequency and motional resistance are also important. With a 10/spl times/ higher power handling capability than the wide-width CC-beam resonator, a comparable series motional resistance, and a 45/spl times/ higher Q of 48 000, the 60-MHz wine glass resonator reference oscillator exhibits a measured phase noise of -110 dBc/Hz at 1-kHz offset, and -132 dBc/Hz at far-from-carrier offsets. Dividing down to 10 MHz for fair comparison with a common conventional standard, this oscillator achieves a phase noise of -125 dBc/Hz at 1-kHz offset, and -147 dBc/Hz at far-from-carrier offsets.