A low phase-noise CMOS voltage-controlled oscillator with a series LC resonator

This paper proposes a novel phase-noise (PN) reduction technique for high performance voltage-controlled oscillator (VCO) using a cross-coupled series LC resonator, rather than parallel LC resonator. While the series connected inductor and capacitor enhances the fundamental frequency swing at the LC connection node, it gives a cleaner spectral purity output and suppresses the overall noise at the drain node of the cross-coupled switching cell. The proposed technique is verified using a 65 nm CMOS process with the VCO operating at around 3.6 GHz frequency range. The phase noise of the VCO is -122.4 dBc/Hz, -125.0 dBc/Hz, and -136.7 dBc/Hz at 600 kHz, 800 kHz, and 3 MHz offset frequencies, respectively, which satisfy the stringent phase noise requirements such as GSM standards operating at 900-MHz, 1800-MHz and 1900-MHz band. The proposed VCO consumes 5.6 mW dc power from a 1-V supply.