Phase Noise Reduction in a VHF MEMS-CMOS Oscillator Using Phononic Crystals

This paper presents experimental results showing reduced phase noise in a very high frequency band microelectromechanical systems (MEMS) oscillator. This has been achieved by engineering the embedded MEMS resonator with phononic crystal structures. The aluminum nitride on silicon MEMS resonator with phononic crystal tethers achieves an unloaded quality factor (Q_u) 2.3 times of the same resonator with a simple tether design. The increase in Q_u leads to a measured 6dB close-to-carrier phase noise reduction in an MEMS-based oscillator that sustained by a transimpedance amplifier implemented in 65nm CMOS process. The 141 MHz MEMS-CMOS oscillator with phononic crystal tethers has a phase noise better than-83dBc/Hz at 1 kHz offset and-134dBc/Hz at the far-from-carrier range while consuming less than 3mW.