Analysis of Phase Noise Dependence on Bias Current in CMOS LC-Tank Oscillators
Date Issued
2009
Date
2009
Author(s)
Li, Cheng-Lung
Abstract
In wireless communication systems, the local oscillator (LO) plays an important role. The local oscillator is usually realized as a frequency synthesizer so as to achieve the stable as well as precise oscillation frequency. Further, phase noise of a frequency synthesizer significantly affects the noise performance of the whole transceiver. In a PLL-based frequency synthesizer, VCO phase noise often dominates PLL phase noise in the 1/f^2 regime. Thus, deeper theoretical analysis is essential to give an objective insight.n this thesis, the relationship between phase noise and bias current is discussed. Noise contributors in a LC-tank oscillator are primarily composed of inductor noise, gate-resistor noise, noise from cross-coupled transistors, and noise from bias circuitry. In a word, tendencies of phase noise vs. bias current will be different due to different noise dominators. More details are discussed in the thesis.n addition, a compact phase noise formula in the 1/f^2 regime for single- and double-switching oscillators is proposed to support qualitative analyses of phase noise. For some given system specifications, like phase noise and power consumption, the sizing prediction can be initially obtained by this compact phase noise formula.hese concepts are realized by the design of a 5.4-GHz CMOS LC-tank P-core VCO. Fabricated in TSMC 0.18-um CMOS mixed-signal process, related measured results are compared with simulation results and theoretical modeling curves to make several conclusions. Finally, the chip including ESD-PADs occupies an area of 1320 x 1190 um^2.
Subjects
Oscillator
Device Noise
Phase Noise
Type
thesis
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