A Passively-Coupled 39.5 GHz Colpitts Quadrature VCO in SiGe HBT Technology

A quadrature voltage controlled oscillator (VCO) using Colpitts topology is presented. The quadrature voltage controlled oscillator (QVCO) facilitates low phase noise due to an innovative coupling mechanism between two differential cores. The passive capacitive coupling operates in-phase, utilizing injection locking technique and is unambiguous in its phase position. A prototype monolithic microwave integrated circuit (MMIC) using heterojunction bipolar transistors in 0.13μm SiGe BiCMOS technology achieves a measured differential output power of 0dBm at the output of each core and a phase noise of -104dBc/Hz at 1MHz offset, with 39.5GHz center frequency of oscillation. The frequency tuning range is 6.4% and power efficiency is 1.25%.