Analysis and design of LC oscillators associated with frequency multipliers: a phase noise perspective

摘要

When a local oscillator signal generation system is based on an LC oscillator and a frequency multiplier, the question of determining the optimal multiplication factor is a key issue. In this paper, the problem is addressed in order to minimize the 1/f(2) phase noise within a tuning range constraint. The analysis, with a practical graphical representation, reveals the oscillator phase noise dependence on the oscillating frequency in the transition from two different regimes, named the inductor-limited quality factor and the capacitor-limited quality factor. The results obtained enable the evaluation of the phase noise performance of systems based on a sub-harmonic and super-harmonic oscillators and how they compare with an oscillator in the fundamental mode. Crucial questions like the phase noise improvement that these systems can achieve are analytically answered. A design methodology is thus proposed and verified through measurements on a frequency source at 31GHz, composed by a sub-harmonic voltage-controlled oscillator followed by an injection-locked frequency tripler, dedicated to backhauling applications, designed on a BiCMOS process technology. The tuning range is 10%, and the phase noise at a 1-MHz offset is -112dBc/Hz. Copyright (c) 2017 John Wiley & Sons, Ltd.