Understand the various biasing methods and tradeoffs in GSM/EDGE mobile unit PA stages
By David Ripley, Technical Director, Skyworks Solutions, Inc.
RF Designline
(06/08/2009 7:00 AM EDT)
A key requirement within the modern mobile-handset power amplifier (PA) is a need to detect and control the transmitted power. This three-part article first explores the various methods of power control for amplifiers operating in both saturated and linear modes. The discussion continues with power detection techniques used in modern handsets. Topics include current, voltage, diode, power, logarithmic (log), and RMS detection, including performance characteristics such as RF bandwidth, video bandwidth, dynamic range, temperature compensation, and VSWR insensitivity.
This three-part series examines the subject as follows:
- Part 1: Power amplifier biasing for power control (click here)
- Part 2: Power detection methods (click here)
- Part 3: Power control feedback (click here)
David S. Ripley received his B.S. degree in electrical engineering from Iowa State University, Ames, in 1992 and the M.S EE degree from National Technical University (NTU), Minneapolis, MN, in 2002. From 1992 to 1999, he worked in the Cellular Subscriber Division, Motorola, Libertyville, IL, where he was involved in the design and development of TDMA and AMPS handsets including RFIC design of receiver and synthesizer functions. Since 1999, he has been with Skyworks Solutions, Inc. (previously Conexant Systems, Inc.), Cedar Rapids, IA, where he has been involved with the design of multiband HBT power amplifiers modules for the GSM and CDMA cellular handsets. He holds seven patents.
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