A 7/24-GHz CMOS VCO with High Band Ratio Using a Current-Source Switching Topology

In this paper, a 7/24-GHz dual-band voltage-controlled oscillator (DVCO) using a current-source switching topology is designed, implemented, and verified in a 0.18-μm CMOS technology for C-band and K-band radar applications. The low- and high-frequency bands are obtained by the Colpitts mode oscillation and the cross-coupled pairs (CCP) mode oscillation, respectively. Unlike conventional dual-band VCOs realized by resonator-switching topologies, the proposed VCO is based on the composite Colpitts and CCP architecture to avoid additional losses in the resonator, or lower its power consumption. The fabricated VCO occupies a chip area of 0.95×0.71 mm2 including all testing pads. Measurements show that the VCO operating in the Colpitts mode provides a phase noise of -112.5 dBc/Hz at 1 MHz offset from the 7.4-GHz oscillation frequency under 7.5-mW power consumption. When the VCO operating in the CCP mode, it provides a phase noise of -99.9 dBc/Hz at 1 MHz offset from the 24-GHz oscillation frequency with 9.7-mW power dissipation. Moreover, the DVCO achieves a high band ratio (fH/fL=24/7) of 3.43. To the authors' best knowledge, the design features the highest band ratio, low power dissipation, and comparable electrical performances among previously reported DVCOs.