Transformer-Coupled 2.5GHz BAW oscillator with 12.5fs RMS-Jitter and 1-kHz Figure-of-Merit (FOM) of 210dB

This paper reports two high-performance parallel resonance 2.5GHz BAW oscillators in 130nm SiGe BiCMOS technology. The proposed architecture concurrently improves 1kHz-FOM by more than 3.8dB together with jitter, and close-in phase-noise performance over prior works and further extends the state of the art in MEMS oscillator design. The design optimizes multiple transformer windings to step-down the high-Q resonator impedance and gain multiple benefits: i) cross-coupled pair size increase without performance tradeoff, ii) reduction in base swing, non-linearity and, flicker noise up-conversion and iii) low-voltage compatible operation. Resistive degeneration and inductive coupling at the BJT emitter are considered. Both topologies achieves <12.5fs RMS-Jitter. Resistive degeneration achieves 1kHz-FOM of 210dB, while the inductively coupled emitter allows for more robust operation.