APN1006 Datasheet | Skyworks Solutions

.Data Sheet.co.kr APPLICATION NOTE APN1006: A Colpitts VCO for Wideband (0.95- 2.15 GHz) Set-Top TV Tuner Applications Introduction Modern set-top DBS TV tuners require high-performance, broadband voltage control oscillator (VCO) designs at a petitive 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. VCO Model Figure 1 shows the VCO model built for open loop analysis in Libra Series IV. Figure 1. VCO Model Built for Open Loop Analysis in Libra Series IV Skyworks Solutions, Inc. - Phone [781] 376-3000 - Fax [781] 376-3100 - sales@skyworksinc. - .skyworksinc. 200316 Rev. A - Skyworks Proprietary Information - Products and Product Information are Subject to Change Without Notice. - July 21, 2005 Datasheet pdf - http://..net/ .Data Sheet.co.kr APPLICATION NOTE - APN1006 This circuit schematic, which is a simple Colpitts structure, uses a series back-to-back connection of two SMV1265-011 varactors instead of a single varactor. This connection allows lower capacitance at high voltages, while maintaining the tuning ratio of a single varactor. The back-to-back varactor connection also helps reduce distortion and the effect of fringing and mounting capacitances. These parasitic capacitances are included in the model as C5, valued at 0.6 p F. This value may change...