Resonant-Inductive Degeneration for Manifold Improvement of Phase Noise in Bipolar LC-Oscillators

Resonant-inductive degeneration of bias current source is described in this paper as a method for a manifold improvement of phase noise in inductance-capacitance (LC) voltage- controlled oscillators. For the verification of this phase-noise reduction method, a test bipolar LC-oscillator has been designed using a phase-noise model obtained from the spectral noise analysis. By forming a resonance at twice the oscillation frequency in the emitter of the bias current source transistor, phase noise of the LC-oscillator is improved by 6 dB. Phase noise of - 112 dBc/Hz at 1 MHz offset from a 5.7 GHz-band carrier has been realized using oscillator with resonant-inductive degeneration, while drawing 4.8 mA from a 2.2 V supply. The test oscillator achieves a frequency tuning range of 600 MHz, between 5.45-6.05 GHz.