Resonant-inductive degeneration for a fourfold phase-noise improvement of a 5.7GHz-band VCO

Resonant-inductive degeneration of tail-current noise in a VCO is presented in this paper. Two test oscillators are described: one designed with, and the other without resonant degeneration. By forming a resonance at twice the oscillation frequency in the emitter of the bias current source, phase noise is improved by 6dB. Phase noise of -112dBc/Hz at 1MHz offset from a 5.7GHz-band carrier and a 5.45-6.05GHz frequency tuning range are realized using oscillator with resonant-inductive degeneration, while drawing 4.8mA from a 2.2V supply.