A fully integrated, 5.6 GHz low‐phase noise Colpitts quadrature voltage‐controlled oscillator (VCO/QVCO) is presented. This QVCO is a complementary cross‐coupled voltage‐controlled Colpitts oscillator with a three‐bit switched capacitor array parallel to the inductor to form LC‐resonant tank and was implemented in TSMC 0.18 μm CMOS technology with 1.8 V supply voltage. Without buffer circuits, measured results achieve a tunable frequency range from 4.81 to 5.75 GHz, corresponding to 17.8%, a phase noise of −121 dBc/Hz at 1 MHz offset frequency from 5.64 GHz, while the QVCO draws 3.8 mA current and 6.84 mW consumption, respectively. Including pads, the chip area is 1.046 mm2 (1.35 × 0.775 mm2). The output power is −10.04 dBm with 50‐Ω termination at the frequency of 5.64 GHz, and the calculated figure of merit is −187.7 dBc/Hz. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1490–1493, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27629