A Tuning Range Extension Technique for Waveform-Shaping Single-Core CMOS Oscillators With No Dedicated Harmonic Tuning

Abstract

This brief presents a tuning range extension technique for output voltage waveform-shaping single-core CMOS oscillators. First, the parasitic capacitors in previous waveform-shaping oscillators that limit the tuning range are analyzed. Next, a triple coupled LC resonator (TCLCR) is proposed to separate the differential-mode and common-mode (CM) resonance path which improves the tuning range significantly. The TCLCR is also able to establish the harmonically tuned impedance without using dedicated harmonic tuning both at CM 2rd harmonic and 3rd harmonic for oscillator’s implicit CM resonance or class-F23 operation to suppress the white noise and flicker noise conversion to phase noise. Finally, as a proof of concept, a 2.79-to-4.9 GHz class-F23 oscillator prototype covering a wide tuning range of 54.9% is designed and fabricated in a 130-nm CMOS technology. The oscillator achieves figure-of-merit with tuning range (FOMT) of 199.4/202.2 dBc/Hz, 196.3/200.9 dBc/Hz and 195/199.7 dBc/Hz at 100-kHz/1-MHz offset from 2.79, 3.83 and 4.9 GHz.