A Single-Switch 3.1–4.7 GHz 194.52-dB FoM Class-D VCO With 495μW Power Consumption

This brief presents an ultra-low-power class-D voltage-controlled oscillator (VCO) designed for GHz applications that mandate decent phase noise performance. A waveform-centric approach of phase noise reduction by controlling the ratio between the floating and single-ended (SE) capacitors in an oscillator tank is proposed. By co-designing an RF choke with the tank inductor to introduce high impedance for the floating capacitors, the optimum capacitance ratio is maintained across the tuning range. The VCO is fabricated in 65nm Bulk CMOS technology and achieves a measured phase noise of −118.36 dBc/Hz and −138.64 dBc/Hz, and figure-of-merit of 192.89 dBc/Hz and 194.52 dBc/Hz at 1 MHz and 10 MHz offset frequencies, respectively. The VCO’s lowest measured $1/f^{3}$ corner is approximately 50kHz, which enables a decent figure-of-merit (FoM) down to a frequency offset of 10 kHz. The VCO features a tuning range of 40% (3.1 GHz - 4.66 GHz) using a one-bit switch to realize two-point modulation in phase-locked loops (PLLs) with milliwatt-level power consumption.