An Ultra-Low Phase Noise Class-F 2 CMOS Oscillator With 191 dBc/Hz FoM and Long-Term Reliability

In this paper, we propose a new class of operation of an RF oscillator that minimizes its phase noise. The main idea is to enforce a clipped voltage waveform around the LC tank by increasing the second-harmonic of fundamental oscillation voltage through an additional impedance peak, thus giving rise to a class-F 2 operation. As a result, the noise contribution of the tail current transistor on the total phase noise can be significantly decreased without sacrificing the oscillator´s voltage and current efficiencies. Furthermore, its special impulse sensitivity function (ISF) reduces the phase sensitivity to thermal circuit noise. The prototype of the class-F 2 oscillator is implemented in standard TSMC 65 nm CMOS occupying 0.2 mm 2 . It draws 32-38 mA from 1.3 V supply. Its tuning range is 19% covering 7.2-8.8 GHz. It exhibits phase noise of -139 dBc/Hz at 3 MHz offset from 8.7 GHz carrier, translated to an average figure-of-merit of 191 dBc/Hz with less than 2 dB variation across the tuning range. The long term reliability is also investigated with estimated >10 year lifetime.