A Quad-Core Dual-Mode Colpitts Voltage-Controlled Oscillator with Octave Tuning Range and Low Phase Noise

In this paper, a novel Colpitts voltage-controlled oscillator (VCO) with low phase noise and an octave frequency tuning range is presented. To achieve low phase noise and a wide tuning range concurrently, the designed VCO employs quad-core-coupled structures, series resonators, dual-mode-coupled inductors, and push–push structures. The quad-core-coupled structures are used for phase noise improvement. The presented series resonators effectively expand the tuning range while reducing phase noise deterioration from amplitude-to-phase modulation (AM/PM) conversion. The dual-mode operation based on coupled inductors and quad-core structures further expands the tuning range. In addition, the adopted push–push structure increases the output frequency. Designed in a 180 nm SiGe BiCMOS process, the proposed Colpitts VCO operates from 7.2 to 14.5 GHz with an octave tuning range of 67.3%. The phase noise ranges from −131.4 to −121.8 dBc/Hz with a peak figure-of-merit (FoM) of 183.0 dBc/Hz and figure-of-merit-tuning (FoMT) of 199.5 dBc/Hz at a 1 MHz offset. The proposed VCO exhibits superior performance in phase noise and tuning range and achieves an octave tuning range for the first time in Colpitts VCOs.