AbstractThis article presents an eight‐phase low phase noise CMOS voltage controlled oscillator (VCO). The low noise CMOS VCO has been implemented with the TSMC 0.18 μm 1P6M CMOS technology and adopts two quadrature cross‐coupled nMOS‐core VCOs injection‐locked through the second‐harmonic. The VCO operates from 5.1 GHz to 5.5 GHz with 7.54% tuning range. The measured phase noise at 1 MHz offset from 5.1 GHz is about −115.4 dBc/Hz. The power consumption of the VCO core is 7.43 mW at the supply voltage of 1 V. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1225–1228, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24270