Single-resonator dual-frequency AIN-on-Si MEMS oscillators

Area of Science:

• Electrical Engineering
• Materials Science
• Microelectromechanical Systems (MEMS)

Background:

• Dual-frequency oscillators require sophisticated interface circuitry for stable operation.
• High quality factor (Q) resonators, like AlN-on-silicon, offer excellent frequency stability.
• Minimizing phase noise is critical for oscillator performance in various applications.

Purpose of the Study:

• To design and implement low-power interface integrated circuits (ICs) for dual-frequency oscillators.
• To optimize the phase-noise performance of oscillators utilizing dual-mode AlN-on-silicon resonators.
• To compare the phase-noise characteristics of different transimpedance amplifier (TIA) topologies.

Main Methods:

• Design and fabrication of two 0.5-μm CMOS transimpedance amplifiers (TIAs) with different topologies (RGC and inverter with shunt-shunt feedback).
• Interfacing TIAs with dual-mode AlN-on-silicon resonators operating at distinct frequency pairs (35.5/105.7 MHz and 35.5/174.9 MHz).
• Incorporation of an on-chip switching network within each TIA for frequency selection.

Main Results:

• Measured phase noise at 1 kHz offset: -114 dBc/Hz (low freq) and -108 dBc/Hz (high freq) for the 35/105 MHz oscillator.
• Measured phase noise at 1 kHz offset: -108 dBc/Hz (low freq) and -105 dBc/Hz (high freq) for the 35/175 MHz oscillator.
• Phase noise below -140 dBc/Hz achieved far from the carrier in all configurations.

Conclusions:

• The developed low-power interface ICs effectively support dual-frequency oscillation with high-Q resonators.
• The inverter with shunt-shunt feedback TIA topology demonstrates superior gain and lower phase noise compared to the RGC topology.
• The study provides valuable insights into TIA design for optimizing phase noise in dual-mode oscillators.