Introduction
Modern set-top DBS TV tuners require high-performance, broadband voltage control oscillator (VCO) designs at a competitive cost. To meet these goals, design engineers are challenged to create high-performance, low-cost VCOs.

The Colpitts oscillator is a traditional design used for many VCO applications. Designing a broadband Colpitts oscillator with coverage from 1–2 GHz requires the selection and interaction of an appropriate varactor diode for its resonator. This application note describes the design of a broadband Colpitts VCO that incorporates the SMV1265-011 varactor diode. This varactor diode was specifically developed at Skyworks for this application. The VCO design, based on Libra Series IV simulation, shows good correlation between measured and simulated performance. This application note includes a board layout and materials list.