An Ultra-Low Close-In Phase Noise Series-Resonance BAW Oscillator in a 130-nm BiCMOS process

MEMS resonators offer excellent alternatives to crystal oscillators with potential cost and area savings from silicon co-packaging/integration. Despite having lower quality factor (Q) when compared to crystals, the availability of a direct low noise high frequency reference offers wider design choices and flexibilities whether be it in addressing close-in or far out phase noise needs – long term clock stability or integrated jitter. Additionally, silicon integration aside from saving cost, dedicated pin for XO and PCB real estate, allows for on-chip thermal compensation around the resonator for superior noise and drift performance. One such promising technology is the bulk acoustic wave (BAW) oscillator [1]. This work reports an indigenous BAW resonator (BAWR) based series-resonance oscillator that provides best-in-class frequency-normalized close-in phase noise (PN) performance $(\gt5$ dB better at 1kHz and lower offsets) along with an excellent Figure-of-Merit (FoM) of -202.5dBc/Hz at 1kHz. The design addresses integrated reference needs for 100+ Gbps multi-lane wireline and multi-channel clocking applications requiring ultra-low PLL jitter for high fidelity and very low BER $(\lt1 \mathrm{x}10^{-12})$.