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

This paper presents an 8.6 GHz oscillator utilizing the third-order antisymmetric overtone (A3) in a lithium niobate (LiNbO3) radiofrequency microelectromechanical systems (RF-MEMS) resonator. 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 Barkhausen’s oscillation conditions for A3 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 Ω-based measurements. The second is an oscillator-divider chain using an on-chip 3-stage divide-by-2 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 L-band PLLs. With further optimization, this work can enable low-power multi-standard wireless transceivers featuring high speed, high sensitivity, and high selectivity in small form factors.