Journal
IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS II-EXPRESS BRIEFS
Volume 68, Issue 2, Pages 538-544Publisher
IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
DOI: 10.1109/TCSII.2020.3043165
Keywords
Flicker noise up-conversion; flicker phase noise reduction; impulse sensitivity function (ISF); cross-coupled oscillators; complementary oscillators; class-C; gate-drain phase shift
Categories
Funding
- Science Foundation Ireland [14/RP/I2921]
- Microelectronic Circuits Centre Ireland
- Science Foundation Ireland (SFI) [14/RP/I2921] Funding Source: Science Foundation Ireland (SFI)
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The article comprehensively reviews the evolution of flicker noise upconversion theories in oscillators and clarifies their controversial and confusing parts. The study identifies that non-resistive terminations in voltage-biased LC-tank oscillators contribute to flicker noise upconversion, and further discusses three mechanisms for reducing phase noise.
A deep understanding of how to reduce flicker phase noise (PN) in oscillators is critical in supporting ultra-low PN frequency generation for the advanced communications and other emerging high-speed applications. Unfortunately, the current literature is either full of conflicting theories and ambiguities or too complex in mathematics, hiding the physical insights. In this brief, we comprehensively review the evolution of flicker noise upconversion theories and clarify their controversial and confusing parts. Two classes of such upconversion mechanisms in voltage-biased LC-tank oscillators (nMOS-only and complementary) are specifically compared and numerically verified using a commercial simulation model of 28-nm CMOS. We identify that non-resistive terminations of both 2nd and 3rd harmonic currents contribute to oscillation waveform asymmetries that lead to the flicker noise upconversion. Further, we discuss three 1/f(3) PN reduction mechanisms: waveform shaping, narrowing of conduction angle, and gate-drain phase shift.
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