An X-Band Oscillator Utilizing Overtone Lithium Niobate MEMS Resonator and 65-nm CMOS

This paper presents an 8.6 GHz oscillator utilizing a third antisymmetric overtone ($A_{3}$) in a lithium niobate (LiNbO3) resonator for 5G communications. The oscillator consists of an acoustic resonator in a closed loop with cascaded RF tuned amplifiers (TAs) built on TSMC RF GP 65 nm CMOS. The TAs bandpass response, set by on-chip inductors, satisfies the Bark-hausen's oscillation conditions for $A_{3}$ while suppressing the fundamental and higher-order resonances. The oscillator achieves a measured phase noise of −56 and −113 dBc/Hz at 1 kHz and 100 kHz offsets from an 8.6 GHz output while consuming 10.2 mW of dc power. The oscillator also attains a figure-of-merit of 201.6 dB at 100 kHz offset, surpassing the state-of-the-art (SoA) EM and RF-MEMS oscillators.