A new class of low phase noise vackar VCO in CMOS technology

In this paper, we present differential Vackar voltage-controlled oscillator (VCO) implemented for the first time in CMOS technology. The Vackar VCO provides good isolation between LC tank and loss-compensating active circuit; thus, excellent frequency stability is achieved over the frequency tuning range. Simple analysis and simulations examine the transistor loading effect and amplitude stability. Results indicate that the Vackar VCO has improved amplitude stability compared to the Colpitts VCO. The improved amplitude stability is favorable for suppressing amplitude-to-phase (AM/PM) noise conversion. Two Vackar VCOs were fabricated to examine their phase noise. C-band Vackar VCO implemented in 0.18 μm RF CMOS shows oscillation frequency ranged from 4.85 to 4.93 GHz. The measured phase noise of the C-band Vackar VCO is -124.9 dB/Hz from 1 MHz offset at 4.9 GHz with a figure-of-merit (FOM) of -188 dBc/Hz. K-band Vackar VCO with gate inductive feedback is implemented in a 0.13 μm RF CMOS process. The oscillation frequency ranges from 19 to 19.95 GHz. The measured phase noise is -103 dBc/Hz from 1 MHz offset at 19.5 GHz with FOM of -182 dBc/Hz.