A 10-MHz Micromechanical Resonator Pierce Reference Oscillator for Communications

Abstract

A modified Pierce circuit topology has been used to first demonstrate a 9.75 MHz µmechanical resonator reference oscillator, then to assess the ultimate frequency stability of such an oscillator via accurate measurement of its close-to-carrier phase noise, which seems to exhibit an unexpected 1/f 3 dependence that limits the phase noise to −80 dBc at a 1 kHz offset from the carrier-a value that must be improved before use in most communications applications. Through theoretical analysis, this 1/f 3 dependence seems to derive from aliasing of active circuit 1/f noise onto the carrier caused by nonlinearity in the capacitive transducer of the µmechanical resonator.

Micromechanical disk array for enhanced frequency stability against bias voltage fluctuations

“…Here, high impedance is defined relative to the impedance presented by the shunt Coi at the resonator I/O terminals, i.e., the resistance presented by the drive/sense circuit loading each I/O port is considered "high" when it is at least 5 times larger than 1/(sCoi). This suggests that to maximize frequency stability against environmental variations, a Pierce oscillator [24] configuration would be a better choice than the commonly used transresistance sustaining amplifier.…”

Modeling and characterization of three kinds of MEMS resonators fabricated with a thick polysilicon technology

“…As a consequence, at least ideally, they do not exert any bending moment on the main beam, so that the main beam is minimally affected by supports and anchors; basically, the supports are used to decouple the main beam from the anchors. This design choice should reduce the so called "anchor losses", which are generally considered as limiting mechanism for the quality factor of RF MEMS [3]. The electrodes were shaped to obtain a high electro-mechanical coupling for the desired (1st or 3rd) mode-shape, i.e.…”

“…The use of such devices as frequency references for RF communication systems is very attractive. Their very high quality factor [2,3] implies a very low phase noise for oscillators including a MEMS resonator as the frequency selective element, D. Paci ( ) IEIIT-Sezione di Pisa, CNR, Via Caruso, 56122 Pisa, Italy e-mail: dario.paci@iet.unipi.it D. Paci · M. Mastrangeli · A. Nannini · F. Pieri Dipartimento di Ingegneria dell'Informazione, Università di Pisa, Via Caruso, 56122 Pisa, Italy which, in turns, implies a very high short term stability [2]. To evaluate their overall performance as frequency references, many studies about long term stability of the resonance frequency [4] and its dependence on the temperature [5,6] have been carried out.…”

Entrainment of Micromechanical Limit Cycle Oscillators in the Presence of Frequency Instability

“…Resonant MEMS have also been fabricated within active-electrical [15], active-optical [16], or natural-optical [17]- [23] feedback loops to demonstrate self-oscillation. In such systems, DC electricity or unmodulated light is converted into harmonic power, making them particularly useful for MEMS clocks [24] or filters [25], if frequency instability is sufficiently low. For MEMS resonators, 1 illuminated within an optical interference field, coupling between displacement and either photothermal stress [17]- [20], [22], [23], [26]- [29], electric charge [21], or light pressure [30]- [36] may lead to a natural closed feedback loop.…”