1/f3 (Close-in) Phase Noise Reduction by Tail Transistor Flicker Noise Suppression Technique

In this paper, a novel circuit method is proposed to reduce 1/f(3) (close-in) phase noise in a cross-coupled LC Voltage Control Oscillator (VCO) by suppressing flicker noise power of the tail transistor. Using an added resistor between drain and gate of the tail transistor, that works as a negative feedback, the tail transistor flicker noise is suppressed, and therefore, the 1/f(3) output phase noise is reduced by 5.7dB. Also, the added resistor helps in better tail current shaping for phase noise reduction. The proposed oscillator is designed in a 0.18 mu m CMOS technology with 1.8V supply and 3.6mW power consumption. Post-layout simulations predict a phase noise of -104dBc/Hz for the proposed oscillator at 100KHz offset from 3.1GHz carrier frequency. Mathematical analysis is included in the paper for confirmation of the phase noise performance enhancement. The Figure of Merit (FOM) of the proposed oscillator is 188.3 and 190.6dBc/Hz at 100KHz and 1MHz offsets, respectively.