APN1006 Datasheet, PDF (1/8 Pages) Skyworks Solutions Inc. – A Colpitts VCO for Wideband (0.95–2.15 GHz) Set-Top TV Tuner Applications

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, broad-
band 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 cov-
erage 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 incorpo-
rates 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 correla-
tion 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 • [e-mail] • www.skyworksinc.com
200316 Rev. A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • July 21, 2005
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