A Low-phase-noise Voltage-controlled Oscillator Based on Wideband Harmonic Shaping

A wideband voltage-controlled oscillator (VCO) with low phase noise is presented.A Class-D topology with a periodically time-varying inductor is adopted in this VCO, and the common-mode resonance extension technique is applied to the resonator. Wideband harmonic shaping is thus achieved, and the phase noise performance across the full operating bandwidth is optimized. Furthermore, the conventional N-channel metal-oxide-semiconductor pair is replaced with a P-channel metal-oxide-semiconductor cross-coupled pair to reduce the superior flicker noise and lower channel thermal noise. Fabricated in SMIC 55-nm CMOS technology, the chip occupies an area of 0.47 mm2, including pads. Measurement results demonstrate that the VCO achieves a continuous tuning range from 3.5 GHz to 5.1 GHz (38.4%). The output power ranges from 7.5 dBm to 7.1 dBm, and a phase noise of -125.8 dBc/Hz at a 1 MHz offset is measured at 3.5 GHz. Operating with a 1.8 V supply voltage, the VCO core consumes 21.3 mA to 23.0 mA, while the output buffer draws 14.4 mA to 15.3 mA. The corresponding figure of merit with tuning range (FoMT) is between 192.4 dBc/Hz and 189.6 dBc/Hz.