The letter highlights the importance of modeling the phase noise of an oscillator using the impulse sensitivity function. A Colpitts oscillator in the common collector configuration is analyzed to obtain an expression for its phase noise. The oscillator design is thus optimized for phase noise with respect to process and design parameters. The fabricated voltage‐controlled oscillator at an oscillating frequency of 52.8 GHz has a measured phase noise of −98.9° dBc/Hz at 1 MHz offset. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:290–295, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27320