A fully-integrated CMOS quadrature VCO implemented with balanced VCOs

A new CMOS quadrature voltage-controlled oscillator (QVCO) is proposed. The LC-tank QVCO consists of two balanced complementary Colpitts VCOs with differential outputs. The tail inductor output of the first balanced VCO is injected to the gate of the tail transistor in the second balanced VCO and vice versa to ensure the two balanced VCOs operate in quadrature. At the supply voltage of 1.2 V, the total power consumption is 4.32 mW. The free-running frequency tuning range is 13.4%, tunable from 5.92 to 6.77 GHz as the tuning voltage is varied from 0 to 2 V. The QVCO has been implemented with the TSMC 0.18 μm CMOS technology and the die area is 0.843 × 1.024 mm2. The measured phase noise at 1 MHz offset is −121.67 dBc/Hz at the oscillation frequency of 6.74 GHz and the figure of merit of the proposed QVCO is about −191.89 dBc/Hz. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:700–703, 2013; View this article online at wileyonlinelibrary.com. DOI: 10.1002/mop.27433