L- and X-Band Dual-Frequency Synthesizer Utilizing Lithium Niobate RF-MEMS and Open-Loop Frequency Dividers

Abstract

This article presents an 8.6-GHz oscillator utilizing the third-order antisymmetric overtone (<inline-formula> <tex-math notation= LaTeX >${A}_{{3}}$ </tex-math></inline-formula>) in a lithium niobate (LiNbO₃) radio frequency microelectromechanical systems (RF-MEMS) resonator. The oscillator consists of an acoustic resonator in a closed loop with cascaded RF tuned amplifiers (TAs) built on Taiwan Semiconductor Manufacturing Company (TSMC) RF general purpose (GP) 65-nm complementary metal-oxide semiconductor (CMOS). The TAs bandpass response, set by on-chip inductors, satisfies Barkhausen’s oscillation conditions for <inline-formula> <tex-math notation= LaTeX >${A}_{{3}}$ </tex-math></inline-formula> while suppressing the fundamental and higher order resonances. Two circuit variations are implemented. The first is an 8.6-GHz standalone oscillator with a source-follower buffer for direct 50-<inline-formula> <tex-math notation= LaTeX >$\\Omega $ </tex-math></inline-formula>-based measurements. The second is an oscillator-divider chain using an on-chip three-stage divide-by-two frequency divider for a ~1.1-GHz output. The standalone oscillator achieves a measured phase noise of −56, −113, and −135 dBc/Hz at 1 kHz, 100 kHz, and 1 MHz 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) oscillators-based electromagnetic (EM) and RF-MEMS. The oscillator-divider chain produces a phase noise of −69.4 and −147 dBc/Hz at 1 kHz and 1 MHz offsets from a 1075-MHz output while consuming 12 mW of dc power. Its phase noise performance also surpasses the SoA <inline-formula> <tex-math notation= LaTeX >${L}$ </tex-math></inline-formula>-band phase-locked loops (PLLs). With further optimization, this work can enable low-power multistandard wireless transceivers featuring high speed, high sensitivity, and high selectivity in small-form factors.