Abstract
This article presents an 8.6-GHz oscillator utilizing the third-order antisymmetric overtone ( A3 ) 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 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 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 L -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.
Highlights
C URRENTLY, the sub-3-GHz frequency bands are too congested to meet the ever-increasing data rates demanded by many cellular users
We develop a direct frequency synthesizer based on integrating an X-band LiNbO3 radio frequency microelectromechanical systems (RF-MEMS) oscillator with complementary metaloxide semiconductor (CMOS) open-loop frequency dividers
Our approach has the following vital benefits: 1) lower-power consumption; 2) a smaller footprint when compared to off-chip XOs/phase-locked loops (PLLs); 3) RF carriers with lower-phase noise/jitter for better receiver sensitivity; 4) spurs-free phase noise for enhancing receiver selectivity; and 5) a faster response and lower-energy dissipation from removing the overhead for XO startup or a PLL locked to an XO
Summary
C URRENTLY, the sub-3-GHz frequency bands are too congested to meet the ever-increasing data rates demanded by many cellular users. Our approach has the following vital benefits: 1) lower-power consumption; 2) a smaller footprint when compared to off-chip XOs/PLLs; 3) RF carriers with lower-phase noise/jitter for better receiver sensitivity; 4) spurs-free phase noise (unlike PLL) for enhancing receiver selectivity; and 5) a faster response and lower-energy dissipation from removing the overhead for XO startup or a PLL locked to an XO. To this end, this article presents an X-band oscillator utilizing a third antisymmetric overtone ( A3) in a LiNbO3 RF-MEMS resonator and 65-nm CMOS.
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